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Full text of "The geomagnetic field, its description and analysis"

D- 



32107 



DEPARTMENT OF TERRESTRIAL MAGNETISM 

M. A. TUVE, Director 

J. A. FLEMING, Director 
(Retired June 30, 1946) 



The Geomagnetic Field, Its Description 

and Analysis 



E. H. VESTINE LUCILE LAPORTE 

ISABELLE LANGE W. E. SCOTT 



CARNEGIE INSTITUTION OF WASHINGTON PUBLICATION 580 

WASHINGTON, D. C. 
1947 



•WT. TERRESTRIAL MA9NETI8W 

SABNEaiE INSTITUTION 

%MHJN«T9N, ©,c, 

3870 7^ 



Lithoprinted from copy supplied by author 

by 

Edwards Brothers, Inc. 

Ann Arbor, Michigan, U.SA. 



December, 1947 



PREFACE 



This book continues a descriptive study of geomag- 
netism begun with Carnegie Institution of Washington 
Publication 578, which was principally concerned with 
the description of the Earth's main magnetic field and 
its secular change. The present volume extends this 
work to the various known geomagnetic variations, with 
inclusion of some analyses. 

To a considerable extent, the present book is actually 
a by-product of Publication 578, since extensive informa- 
tion on geomagnetic variations was required for the im- 
proving of estimates therein of geomagnetic secular 
change for the period 1905 to 1945. Because the latter 
required descriptive information respecting shorter- 
period time -variations on a world-wide scale and over 
these many years, the general scope of coverage is con- 
siderable. Moreover, the emphasis has been upon the 
description rather than upon the interpretation of results. 

It is believed that the two volumes together comprise 
the first convenient detailed compendium of geomagnetic 
data especially suited to the needs of those engineering 
workers who are mainly concerned with the practical ap- 
plications of geomagnetism. The wide use of illustrative 
diagrams (many initially drawn as a training exercise for 
the draftsmen who drew the maps of the first volume) en- 
hances the effective description of geomagnetic phenom- 
ena of our environment. The books emerge therefore as 
a kind of picture supplement to the standard treatise 
Geomagnetism : the writer hopes that his teacher, Pro- 
fessor Chapman, senior author of that treatise, will not 
object to such suggestion, provided he be not held at fault 
for any mistakes that we may have made. 

In the course of pursuing the major descriptive ob- 
jectives of this war project, the writers could not resist 
the temptation to undertake some serious investigations 
of the extensive new data available. Hence attempts at 



explanation of certain phenomena will be found at inter- 
vals, between the stacks of figures and tables, along with 
some short discussions linking the present with previous 
work. The writers hope that in this way a more interest- 
ing and readable account has been provided. 

The writers wish to thank our many coworkers whom 
we represent as authors of this volume. We wish to re- 
cord especial indebtedness to Dr. J. A. Fleming for ma- 
terial assistance over a period of several years. We 
have benefited much also by the interest and encourage- 
ment of Dr. M. A. Tuve, Director, which facilitated 
the speedy production of a book including much trouble- 
some detail. Among our many other coworkers, there 
were especially valuable contributions by E. Balsam, 
N. Davids, W. N. Dove, H. D. Harradon, D. T. Heck, W. 
C. Hendrix, H. F. Johnston, CM. Martin, R. Mason, H. 
M. Myers, A. M. Palmer, W. E. Scott, J. W. Smith, M. B. 
Smith (administrative matters), E. J. Snyder, and O. W. 
Torreson (publication). We wish also to mention the 
skilled assistance of R. E. Tritt in the operation of 
punched-card computing equipment. 

Finally, grateful acknowledgment is made to the Naval 
Ordnance Laboratory, United States Navy Department, for 
the financial help covering this work and report; it is a 
pleasure to record also our appreciation to the Naval 
technical representative, Dr. G. H. Shortley, now of Ohio 
State University, whose quick grasp of the problems of 
geomagnetism facilitated execution of this project. 

This volume completes a final report on work done 
for the most part during the war period 1942 to 1946 
under Contract NOrd-392. 



E. H. Vestine, 
Department of Terrestrial Magnetism 



iii 



Digitized by the Internet Archive 

in 2012 with funding from 

LYRASIS Members and Sloan Foundation 



http://archive.org/details/geomagneticfieldOOcarn 



CONTENTS 

CHAPTER I n 

Page 

Introduction 1 

1. General scope of descriptive data of volume 1 

2. Analyses of geomagnetic fields 1 

CHAPTER II 

The Earth's Main Field and Its Analysis 3 

1. Scope and data 3 

2. Method of analysis 3 

3. Results of analysis 4 

4. Estimate of external part of field 4 

5. Test of Schrodinger's new field theory 4 

6. Comparison of present with earlier analyses 4 

7. The geomagnetic poles for epoch 1945 4 

8. The main field within and beyond the Earth's atmosphere 5 

9. Effect of the electric currents causing geomagnetic variations and disturbances upon 

the computed values 5 

10. Table of the Earth's surface potential of main field 5 

11. Charts of vertical gradients of field components 5 

12. Simple electric current functions at various depths reproducing main field at Earth's 

surface, or those for the residual part 5 

Tables 1-32 7 

Figures A-G and 1-8 25 

CHAPTER III 

Geomagnetic Secular Change and Its Analysis 35 

1. Introductory remarks 35 

2. Data analyzed 35 

3. Secular -change values at various heights 35 

4. Secular change in V 35 

5. The vertical derivatives of field components of secular change at various epochs .... 35 

6. Current functions at various depths, reproducing secular change at the surface of the 

ground 36 

Tables 33-101 37 

Figures 9-28 ; 73 

CHAPTER IV 

The Geomagnetic Variation With Sunspot-Cycle, RV 85 

Figures 29-34 87 

CHAPTER V 

The Geomagnetic Annual Variation, AV 93 

1 . General remarks 93 

2. The annual variation for all days, Polar Year, 1932-33 93 

3. The latitude distributions of the symmetrical and sinusoidal parts of the annual variation 94 

Table 102 . . '. 96 

Figures 35-46 97 

CHAPTER VI 

The Geomagnetic Post-Perturbation, P 119 

1. General remarks 119 

2. The latitude distribution of the post-perturbation, P 119 

Figures 47-49 121 

CHAPTER VII 

The Solar Daily Variation on Quiet Days, S q 129 

1. Previous studies of Sq, scope of present work 129 

2. The solar daily variation on international quiet days by seasons and year, Polar Year, 

1932-33 129 

3. The solar daily variation on international quiet days, by months, seasons, and year, 

1922 to 1933 129 

4. The dependence of Sq on longitude 130 

5. The variation in the amplitude of Sq with sunspot-cycle 130 

6. The daily variability of S q 130 

Table 103 132 

Figures 50-87 133 



CONTENTS 



CHAPTER VIII 

Page 

The Disturbance Daily Variation, S D , and Storm-time Variation, D S { 171 

1. Introduction 171 

2. Disturbance daily variation, Sd, on disturbed days , by seasons and year, Polar Year, 

1932-33 . . 172 

3. Disturbance daily variation, Sd, by months, season, and year, 1922 to 1933 172 

4. Disturbance daily variation, Sd, by months, season, and year, for various parallels 

of latitude 172 

5. Variation of Sd with longitude 172 

6. The storm-time variation D s t 172 

7. The values of Sd and Dst on individual days of storm 173 

8. The irregular geomagnetic disturbance Dj 173 

9. The latitude distributions of noncyclic change, NC 174 

Figures 88-128 175 

CHAPTER IX 

Frequencies of Geomagnetic Fluctuation of Various Intensities and Durations 257 

1. General remarks 257 

2. Magnetic variometers 257 

3. General theory of magnetic variometers 1 258 

4. Solution of the response equation 259 

5. Experimental determinations of responses of la Cour variometers to various impressed 

fields 261 

6. Estimates of magnitudes of micropulsations in the Earth's field 262 

7. Comparison of calculated responses of magnetic variometers with observation 262 

8. Stability of magnet-system 262 

9. Effect of change in damping on the response of variometer 262 

10. Survey of world-wide distribution of ranges with time in magnetic elements, horizontal 

intensity (H), declination (D), and vertical intensity (Z) 263 

11. Survey of weekly, monthly and yearly ranges in magnetic fluctuations 264 

12. Tables of probabilities and expectations of ranges in magnetic elements 265 

13. Isochronic charts showing expectations of ranges in H, D, and Z 265 

14. Survey of short-period magnetic fluctuations 265 

15. Latitude distribution of fluctuation 268 

16. Frequency distribution of fluctuations of duration five minutes to ten hours 268 

17. Geographical distribution of short-period magnetic fluctuations • 268 

18. The nature of magnetic fluctuations and their possible current systems 269 

19. Dependency of frequency and magnitude of small fluctuations on magnetic activity .... 270 

20. Short-period magnetic fluctuations on land compared with those over or within ocean 

areas 270 

21. Measurements of fluctuations of very short period with instruments of improved 

response and increased time resolution 270 

22. Fluxmeter apparatus 271 

23. Fluxmeter installation at Cheltenham, Maryland 271 

24. Fluxmeter installation at College, Alaska 271 

25. Results of fluxmeter measurements, Cheltenham and College 272 

26. Unusually large short-period geomagnetic fluctuations measured at Ivigtut, Greenland . 273 

27. Background, very small short-period fluctuations at Turtle Mound, Florida, with port- 

able magnetograph 273 

Tables 104-125 275 

Figures 129-226 297 

CHAPTER X 

Magnetic Storms and Associated Phenomena 357 

1. Introduction 357 

2. The electric current system 357 

3. The polar field of magnetic storms 357 

4. The electric current systems for individual hours of storm 358 

5. Earth current system of magnetic bays 361 

6. Association of magnetic disturbances with ionospheric phenomena and cosmic rays . . . 361 

7. Solar radiation responsible for magnetic disturbance and allied phenomena 362 

8. Statistical fluctuations in stream density 362 

9. Rocket experiments 363 

Figures 227-241 365 

CHAPTER XI 

Prediction of Geomagnetic Fluctuations 375 

1. General remarks 375 

2. Bases for prediction 375 

3. Formal methods of prediction 375 

4. Measures of magnetic activity 375 

5. Relation of average auroral and geomagnetic characteristics 376 

6. The prediction of the systematic geomagnetic variations 376 

Tables 126-129 377 

Figures 242-250 381 

Literature Cited 388 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 

CHAPTER I 
INTRODUCTION 



1. General scope of descriptive data of volume. - -The 
present volume supplements the descriptions of geomag- 
netic phenomena given in a previous volume [1] which 
was devoted largely to the technique and results of map- 
ping of the main magnetic field of the Earth and its secu- 
lar change. The descriptions are here extended to in- 
clude results of measurements of various geomagnetic 
variations, usually for all available well-distributed ob- 
servatories. The new compilations are based in most 
cases on large samples of homogeneous data. Where av- 
eraged variations appear, these cover, in so far as pos- 
sible, exactly the same time intervals at all observato- 
ries. Moreover, the time intervals used have been 
lengthened to include from one to three sunspot-cycles. 
Certain variations such as, for instance, the solar daily 
variation, are given in the form of 12-year averages by 
months rather than as an average by seasons and an in- 
dividual year. Indication of the amplitude of the solar 
daily variation on every day for a period of approximate- 
ly 40 years is likewise provided as being interesting be- 
cause of its connection with ultraviolet radiation from 
the Sun. In the case of the disturbance daily variation, 
the average characteristics are shown for the first time 
on a world-wide scale (except in very high latitudes) for 
each month of the year throughout a sunspot-cycle. In- 
cluded also are new data for the annual variation, post- 
perturbation, noncyclic change, and geomagnetic varia- 
tion with sunspot-cycle, usually not previously deduced 
at more than a few stations. For many of these effects, 
data are given which are appropriate to almost all avail- 
able observatories, throughout the period 1900 to 1942. 

Hourly estimates of the storm -time and disturbance 
daily variation are made for a period of one year for low 
latitudes. Previous studies descriptive of the average 
storm -time variation in low and middle latitudes have 
also been extended, and the new data have been used to 
estimate storm-time variation in high latitudes. Hourly 
features of selected magnetic storms are considered on 
a world-wide scale. In addition, many new data are pro- 
vided and summarized relating to various short-period 
geomagnetic fluctuations. 

2. Analyses of geomagnetic fields. --A few geomag- 
netic fields have been subjected to potential analysis. In 
this way, the geomagnetic phenomena are perceived not 



only as measured at the Earth's surface, but also as 
they appear in adjacent regions, within the Earth, and 
within the atmosphere. Finally, causes, known or prob- 
able, of the various fields are discussed. 

First on the list of great phenomena not yet under- 
stood is the Earth's main field and its secular change. 
There should, of course, be no such attribute of nature, 
so far as present day facts regarding the probable char- 
acter of the Earth's interior are concerned. But its ex- 
istence is verified by experiment, and its description in 
mapped form as given in a previous volume is subjected 
here to analysis. Chapters II and III include the results 
of such analysis, with calculated values of the field in 
the atmosphere and beyond, and of simple current func- 
tions at various depths within the Earth that could pro- 
duce it. It is concluded that the site where it originates 
may be in the region from, say, 1000 km to 3000 km 
depth within the Earth. 

The potential and space gradients of the main field 
and secular change are calculated and described for the 
Earth's surface. 

The results of some analyses of average features of 
various geomagnetic variations are also discussed, with 
particular reference to the average current systems re- 
sponsible for those features. 

In later chapters of this volume, there are consider- 
ed mainly some features of individual rather than aver- 
aged geomagnetic and allied phenomena. These studies 
relate chiefly to magnetic storms, bays, and accompany- 
ing ionospheric and cosmic-ray effects. Search is made 
for evidence of effects in magnetic disturbance of incom- 
ing particles of various energies. 

Finally, the field patterns of short-period geomagnet- 
ic disturbances are derived, on the basis of data from 
various magnetic observatories, especially those of the 
Polar Year 1932-33. There are provided also extensive 
statistical compilations relating to the frequency of small 
disturbances of various amplitudes and durations. These 
are tentatively discussed in relation to possible charac- 
teristics of various incoming solar streams of particles. 

In conclusion, a few remarks are appended concern- 
ing important outstanding problems of geomagnetism 
that challenge the attention and talents of future investi- 
gators in physical research. 



CHAPTER II 



THE EARTH'S MAIN FIELD AND ITS ANALYSIS 



1. Scope and data. — A new and improved description 
of the Earth's main field (Figures A to G, presented at 
the end of this chapter) and its secular change, gleaned 
from the magnetic observations of the past four decades, 
was presented in a preceding volume [1]. The general 
aim was that of marshalling the information in a form 
suited to practical applications of geomagnetism, with a 
descriptive summary of new procedures used in attempt- 
ing to obtain improved isomagnetic charts. The present 
treatment seeks to emphasize those features of purely 
scientific interest more adequately, the power of descrip- 
tion being enhanced by analysis. For instance, the anal- 
yses permit the description of the main field in extensive 
regions adjacent to the Earth's surface and of attributes 
of this field not yet susceptible of measurement. These 
are of both practical and theoretical import. 

From spherical harmonic coefficients there are com- 
puted on a world-wide scale the smoothed gradients of 
field in certain directions which are of interest in geo- 
physical prospecting. Similar calculations are made of 
the potential of the main field, but disregarding a possible 
constant unlikely to be of consequence. Tentative posi- 
tions of the geomagnetic poles for epoch 1945 are given. 
There are also included calculated spherical current 
sheets at various depths which could reproduce the re- 
sidual part of the main field. These afford one of the 
simplest modes of representing the observed features of 
the field. Finally, these are discussed in relation to the 
probable depth at which we may seek the cause of the field. 

The first spherical harmonic analysis of the main 
field was made by Gauss [2]. He proved that this field 
was almost entirely of internal origin. This was clearly 
a definite advance in the understanding of geomagnetism. 
Since the time of Gauss at least a dozen additional analy- 
ses have been made [3]. It seems that there has been 
consciousness of gradual improvement in the quality and 
quantity of magnetic observations. Consequently there 
has been, on the average, one such analysis per decade, 
though they seem to have appeared in groups. They have 
yielded coefficients of mathematical functions represent- 
ing the main field, and the changing values of the coeffi- 
cients have indicated how the main field, split into con- 
venient component parts, has varied with time, part by 
part. 

2. Method of analysis. --The procedures used here 
were similar to those used by Dyson and Furner [4] in 
their analysis of the British Admiralty charts of the mag- 
netic field for 1922, and there were employed tabulations 
of the spherical harmonic functions of Schmidt [5]. 

A magnetic potential V over the Earth's surface can 
usually be expressed in terms of the series [3] 

ce> n 
V = a £ 2 
n = m = 

,, m w / x n+ll . m 
+ (l-c n )(a/r) \A cos mX 

( in, . .n . m w , >n+11„ m . -i ,.,> 
+ {s n (r/a) + (l-s n )(a/r) JBj, sin mXj..(l) 



in 



(cos£>)[{ 



m , n 
c„ (r/a) 



where a_is the radius of the Earth, r the distance from 
the Earth's center, B the colatitude, and X the east lon- 
gitude; c n m and s n m are numbers lying between zero and 
one, representing the parts of the harmonic term P n m cos 

are due to 
are coeffi- 



m0 or P n m sin m0 , in v, which at r 



B 



matter outside the Earth. Also A 

cients usually sought in analysis. For the order m and 

degree n with m < n > 0, we have in the case m > 

P n m (cos 6) ={2(n-m)!/(n + m)!} l/2 P nm (cos 6) 



and when m = 



P n m (cos 6) 



P n;m (cos0) 



The function 



P nm (cos 6) = sin m 6 d m P n (cos 0)/d(cos 6 ) m 

may be written 

r> /„ a\ (2n)! . m „/ n-m fl 

P m (cos 6) = n i sin 0^ cos 6 
"> U1 2 n!(n-m)! I 



(n-m)(n-m-l) cos n-m-2 ( 
2(2n-l) 



+ (n-m)(n-m-l)(n-m-2)(n-m-3) cos n-m-4, 
2.4(2n-l)(2n-3) 



so that, for example, P2 i(cos 6) = 3/2 sin 2 6 . 
It is convenient here to define the functions X r 



....} 



m 



dP n u (cos 6 )/nd0 , and Y n 



m 



mP n (cos 6)/n sin 6, 
which together with Pn = Pn (cos 6 ) have been ex- 
tensively tabulated by Schmidt [5]. 

Noting that the north, east, and vertical intensities 
are X = dV/rdd , Y = - dV/r sin 6d\, and Z = dV/dr, 
respectively, at r = a we obtain from (1), drooping sum- 



m 



_ -o m 
- e n 



mation signs, and putting nA n u = A n , nBn 

X = X n (A n cos mX + B n sin mX) 

Y = Y n m (A n m sin mX - B n m cos mX) 

Z = P n m [{ nc n m - (n + l)(l-c n m )}(A n m /n)cos mX 

+ {ns n m - (n+l)(l-s n m )}(B n m /n)sin mX)] 

If c n and s n m are zero, in which case the field is en- 
tirely of origin internal to the Earth, 



...(2) 



Z = -P. 



mr(n+ 
n L n 



(n+1) . m 

- A n cos mX 



n+1 _ in 

—— B n sin mX 



] 



If c n and s n are not zero, we may analyze Z (at r 
a) in the form 

Z = P (a cos mX + (6 n sin mX) 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



m 



whence knowing a n and /3 n we evaluate c n and s n 
from the relations 

a n m ={nc n m -(n + l)(l-c n m )}A n m /n| ^ 

^={ns n m -(n + l)(l-s n m )}B>j 

The immediate problem here is that of finding the val- 
ues of A n m and B n m from world charts of the main field 
separately for X and Y, and likewise the values of a n m 
and j3 n m from the corresponding chart in Z. 

This is conveniently done by first analyzing the ob- 
served values of X, say, along parallels of colatitude in- 
to Fourier coefficients a m , b m of the series a m cos mX 
+ b m sin mX . The coefficients a m , bm are functions of 
colatitude only. These are next fitted by the functions 
X n m , for corresponding values of m, where m<n, by 
solving sets of linear equations to obtain the values of 

Tables 1, 2, and 3, presented at the end of this chap- 
ter, list in condensed form the data of the analyses. The 
actual data consist of new charted values of X, Y, and Z 
at 10°-intervals of latitude and longitude for epoch 1945.0. 
Values of am, b m along each 10° parallel of colatitude 
10°<8 5-170° were found for m<6, using 36-ordinate 
Fourier analyses and the more complete listing of values 
of the previous volume [1]. Weights w were assigned as 
follows: 



for 8 = 10° and 170°, w = 1; 8 = 20° and 160°, w = 2 

6 = 30° and 150°, w = 3; 9 = 40° and 140°, w = 5 

8 = 50° and 130°, w = 7; 8 = 60° and 120°, w = 8 

8 = 70° and 110°, w = 9; 8 = 80°, 90°, and 100°, 

w = 10. 



and thus were nearly similar to weights used previously 
by Dyson and Furner [4]. Normal equations were formed, 
the coefficients A n m , B n m being, on solution, given in 
terms of a m , b m - In fact, since weights were assigned 
symmetrically about 8 = 90°, the values A n or B n m 
were in no instance calculated by a process more com- 
plicated than summing (using predetermined factors from 
matrix-elements) three products involving am or bm- 
These same factors could again be used in later analyses 
of isoporic charts, where similar weights were assigned. 
3. Results of analysis. --Table 4 lists the coefficients 
of equation (2) for values up to n = 6, as found from anal- 
yses of the values of X, Y, and Z for 1945.0. On the 
whole, the coefficients found independently from analyses 
of X and Y show rather good agreement. Tables 5 and 6 
list observed minus computed values for X and Y. 



m 



4. Estimate of external part of field. --Values of c n , 
s n m were computed by meaning values of the coefficients 
An™, B n m derived from X and Y (except for zonal har- 
monic terms given by X alone). As was suggested by 
Dyson and Furner [4], the existence of an external part 
was not indicated with any great degree of certainty. In 
fact, though most values of c n m , Sn up to m = 3 and 
n = 3 indicated a few per cent of the field to be of exter- 
nal origin, the value of c-f was 0.000. It seems likely 
that Cj0 should be the largest fraction, yet our analysis 
for this component gives an external part less than 1 
per cent. In fact, our analysis-probably does not reveal 
the existence of any permanent external source of field. 

Table 7 lists observed minus computed values of Z, 
based on adopted coefficients obtained from appropriate 
means of the coefficients for X and Y. The agreement 



is so good, considering the necessarily smoothed char- 
acter of the computed distribution, that there seems little 
likelihood of an important contribution of external origin. 

5. Test of Schrodinger's new field theory. --Schrod- 
inger [6] has recently sketched a new unitary field theory 
for the gravitation, meson, and electromagnetic fields. 
One of the highly interesting consequences of the theory 
is that there should exist an external and nonpotential 
part of the main field of the Earth. Moreover, the verti- 
cal component of curl of field should not vanish but should 
vary with longitude. We have looked for this variation in 
longitude without success, using values of curl only for 
areas of chart without adjustments to give zero curl val- 
ue. These results are apparent from Table 8. 

We believe our charts to be more accurate than those 
of 1885 used by Schrodinger , and the estimated values of 
curl in the new charts are definitely of small average 
value. 

This- does not mean that Schrodinger's theory is nec- 
essarily incorrect, but rather that the constants he eval- 
uates from the charts for 1885 are incorrect. We like- 
wise find that the external field is probably very small, 
which on his theory presupposes a small value of the ver- 
tical component of curl. 

6. Comparison of present with earlier analyses. — 
Since we cannot definitely ascribe a small part of our co- 
efficients of Table 4 to an external field, we write 



gn 



m . m . m/„. . m tj m t, m/„ 
A n = A n /n; h n = B n = B n /n 



and obtain the Gauss coefficients (external plus internal) 
for our analysis. In Table 9 these are compared with 
those of previous analyses. The significance of these co- 
efficients as indicators of secular change will be discussed 
later, when our spherical harmonic analyses of isoporic 
charts at various epochs are presented. 

7. The geomagnetic poles for epoch 1945. --The first- 
degree terms in V/a may be written [3] 

v l /a = gi°Pi° + (gi 1 cos X + hj 1 sin XjPj 1 

= gj cos 8 + (gj cos X + hj sin X)sin 8 

Writing 

H = (gl ) + (§1 ) + ( h l ) i cos 6 = §1 / H o> 

tan X = hjVgj 1 

cos 9 = cos 8 cos 8q + sin 8 sin 8q cos(X-Xq) 

so that is the angle between the direction ( 8, X) and 
the special direction (0n, *o)- M tnen follows that 

Vj = H cos 9 

which is the same as that of a sphere uniformly magnet- 
ized along the direction (- 8q, -Xo), with equatorial hor- 
izontal intensity Ho- 

For 1945 we find for latitude and longitude of the 
north geomagnetic pole,<*> = 78°.6 N, X = 289°.9 E, 
and for the south magnetic pole, <£ = 78°.6 S, X = 
109°. 9 E. The magnetic moment of the Earth given by 
M = H a 3 is found to be 8.06 X 10 25 CGS. 

The 1945 values of <#>, X differ from those for 
1922 [3] (<f> = 78°.5, X = 291°.0) by -0°.l in tf> and 
-l°.l in X. 







THE EARTH'S MAIN FIELD AND ITS ANALYSIS 



8. The main field within and beyond the Earth's at- 
mosphere. --The components X, Y, and Z at any height 
h = r -a above the Earth's surface can be computed from 
expressions obtained on differentiating equation (1). These 
have been computed with IBM (International Business 
Machines) automatic (punched-card) machines, using 48 
coefficients derived from those for X and Y in Table 4, 
assuming c n m , Sn m to be zero .and are given in Tables 
10 to 24. The importance of c n , s n m will increase 
with increasing height h, since, if they are not zero, the 
terms in (r/a) n by which they are multiplied in (1) will 
increase rapidly with increasing r when n is large. 
However, the approximation for the internal contribution 
of the main field at various heights should be almost as 
good as indicated in the comparisons of Tables 5 to 7. 
The accuracy of the computations is expected to decrease 
as h increases, since the process is fundamentally one of 
analytic continuation. However, at modest heights the 
synthesized values might well give a better fit with ob- 
served values, if the latter are available, than at the 
Earth's surface, since we cannot hope to represent the 
field accurately at the Earth's surface with the harmon- 
ics up to degree six. Harmonics of very high degree 
would be needed to represent magnetic anomalies. Thus 
the main field at the Earth's surface is more complex 
than the present isomagnetic charts indicate, but it sim- 
plifies rapidly, without sensible contribution from high- 
degree harmonics, at modest heights. The computed val- 
ues of X, Y, and Z have application in electromagnetic 
problems of the ionosphere, and they may find practical 
application also in the guidance of air-borne vehicles and 
rockets. 

In some applications it may be of interest to have 
computations of D, H, I, and F at various heights. 
These can be speedily computed with the usual simple 
formulas from the values of Tables 10 to 24, but we have 
not undertaken this. For instance, tan D = Y/X, and 
H = (X 2 + Y 2 ) 1 ' 2 , at any height, where X and Y are the 
tabular values for that height. 

Charts of the main field at great heights must neces- 
sarily be especially simple. The greater the height, the 
more closely will the charts resemble those for the cen- 
tered dipole of the main field. 

9. Effect of the electric currents causing geomagnet- 
ic variations and disturbances upon the computed values. 
— Within the upper atmosphere there flow varying elec- 
tric currents in ionized regions. Except near the auroral 
zone, the electric conductivity varies slowly in any hori- 
zontal direction. Hence the electric currents are expect- 
ed to have magnetic fields like those of thin, nearly uni- 
form current sheets. Since their heights are usually 
small compared with the lateral dimensions of current 
flow, the field near these currents will not be very dif- 
ferent in magnitude from that observed at the Earth's 
surface. Proceeding upwards along any radius r the 
values of Z will be continuous and those of X (or Y) 
discontinuous on crossing the current sheet. 

Within two narrow belts of latitude, the northern and 
southern auroral zones, large and concentrated ejectric 
currents flow during strong and frequent magnetic dis- 
turbances [3]. At points near these currents, the field 
will vary nearly inversely as the distance to the current. 
However, very near the current, the field would scarcely 
be expected to exceed that of the main field itself, which 
presumably acts in some way as the guiding principle 
which brings it into being. Thus these currents, except 
under special circumstances and only within quite special 



regions, would seldom modify the computed values ap- 
preciably and then only by a few per cent. 

The auroral-zone currents, on an average, are ex- 
pected to be largest in the early morning and late after- 
noon, local time, and very small near noon and early 
evening. 

10. Table of the Earth's surface potential of main 
field . --Table 25 shows the potential calculated from syn- 
thesis of the 48 spherical harmonic terms. So far as we 
are aware, this is the only tabulation of the potential pub- 
lished since that of Gauss, a century ago. As expected, 
its characteristics are simpler than those for its space 
gradients or for the components of field. Table 26 gives 
the potential of the residual field (terms in PjO and Pjl 
removed). 

11. Charts of vertical gradients of field components. 
--Tables 27 to 29 give computed values for the vertical 
gradients of X, Y, and Z. 

Should the sources responsible for the main field be 
distributed within a layer of great thickness within the 
Earth, there arises an interesting point in connection 
with the charts of vertical gradients. Such charts reflect 
best the effects of sources quite near the Earth's surface. 
The distribution of potential at the Earth's surface, on the 
other hand, may include much greater proportionate con- 
tributions from distant internal sources than in the case 
of the gradients. 

However, the dipole terms (those with m = or 1, 
n = 1) dominate among the contributions of various har- 
monics of the main field. Hence the nondipole contribu- 
tions in the derivatives of X, Y, Z with respect to r 
also have been synthesized. These results are shown in 
Tables 30 to 32; they apply to what is usually called the 
residual field of the Earth. 

The complexities in pattern are now more evident, 
but it seems difficult definitely to relate them, say, to 
the surface distribution of continental areas, or to any 
other known geophysical phenomenon. The results seem 
compatible with a somewhat simple, broad distribution of 
sources with depth. However, they are also compatible 
with a distribution of sources within a thin layer. 

12. Simple electric current functions at various 
depths reproducing main field at Earth's surface, or 
those for the residual part. — There is a possibility that 
the main field is due to electric currents flowing within 
the Earth. If so, these are likely to be maintained con- 
tinuously by some mechanism not yet understood [7]. 
There is even a theoretical and somewhat academic pos- 
sibility that they might consist of a freely decaying sys- 
tem, a survival of some old order of things, provided the 
electric conductivity within the Earth approaches super- 
conductivity [8]. 

The studies of Chapman [3] and of Lahiri and Price 
[9] suggest very rapid increase in conductivity with depth 
near 700 km. Their estimates of conductivity were in- 
ferred from consequences of electromagnetic induction 
in relation to geomagnetic variations of aperiodic char- 
acter lasting a few days. 

Chapman and Whitehead [3] also inferred that the mag- 
netic permeability of the Earth was about unity to depths 
of a few hundred km. Moreover, the percentage content 
of magnetic material in surface rocks probably averages 
less than 1 per cent. At a modest depth, a few tens of km, 
the Curie point will probably be reached, judging from the 
experiments on shift of Curie point with increasing pres- 
sure [10]. Under these conditions, the magnetic charac- 
teristics of the Earth's interior may closely resemble 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



those for free space, for a depth approaching that for the 
source of main field nearest the Earth's surface. Thus 
we may be able to calculate the main field at various 
depths within the Earth, from the spherical harmonic co- 
efficients at the Earth's surface. The defects in the ana- 
lytic continuation at the greater depths may be the only 
important factor limiting accuracy, rather than the small 
amount of magnetic matter known to exist in the Earth's 
crust. 

We have not computed the field at various depths but 
have evaluated instead the current distribution over sev- 
eral thin spherical sheets, each concentric with the 
Earth. Any one of the computed distributions could re- 
produce the residual part of the main field at the surface 
of the ground. 

Figures 1 to 8 give the current functions J for depths 
0, 1000, 2000, and 3000 km for the main field and for the 
residual field. These become more complicated with in- 
creasing depth. They are found by summing the typical 
terms 

J n = (10/47r)[(2n+],)/n] V n (a/r) n+1 

where J n is the current function in amperes, a the radi- 
us of the Earth, r the radius of the spherical current 
sheet and V n its potential at (r, d). 

It will be noted that the quantity (a/r) n+1 becomes in- 
creasingly important as r diminishes, especially for 
larger values of n. Moreover, the series in V n at r = a 
does not converge rapidly. There are in fact neglected 
surface terms of degree greater than six needed to im- 
prove the fit of the potential at the Earth's surface. This 
means that the complex configuration for J shown for 
depth 3000 km is almost certain to be much too simple. 
Thus the current systems due to the thermoelectric 
forces recently discussed in a valuable and interesting 
series of papers by Elsasser [11] would be exceedingly 
complex. A highly complex current pattern is of course 



not impossible, yet we very much doubt from our work 
here that these currents arise from a depth as great as 
that postulated by Elsasser. 

In drawing our isomagnetic charts over ocean areas, 
we believe we have noted indications of possible anoma- 
lies 1000 to 2000 km in linear cross-section. These a- 
nomalies may be only apparent rather than real, a con- 
sequence of defects in present survey data. However, it 
is our present opinion that they are very likely to be real, 
a point which could now be readily verified by means of 
measurements of total intensity by aeroplane [12]. Such 
anomalies could not arise from sources at 3000 km depth, 
except possibly through combinations of fantastic current 
patterns. 

Smaller anomalies could and do arise in the Earth's 
crust.* Anomalies of cross-section somewhat similar to 
the depth "of the. Earth's crust taken, say, to the Curie- 
point isotherm, are unlikely to arise from deeper sources. 
There is need for study of such anomalies, and an oppor- 
tunity for important scientific contribution by those insti- 
tuting magnetic surveys by aeroplane. It seems likely that 
some of these anomalies, because of their size, should be 
ascribed to sources within the mantle, and not to sources 
at depths as great as that of the central core. 

We conclude that if the main field is due to electric 
currents the principal region of flow is likely to be below 
1000 km but above 3000 km depth. 

The current patterns calculated at various depths like- 
wise give the strength of equivalent magnetic shells in 
electromagnetic units at those depths, on dividing the 
current shown in amperes by ten. With this model, the 
permissible ranges in depths of source will be from 
about 3000 km depth and upwards almost to the Earth's 
surface. However, the surface rocks do not show any- 
thing approaching the degree of magnetic polarization 
required, and the Curie point for magnetic materials is 
reached at a few tens of kilometers. 



TABLES 1-32 



Table Page 

1-3. Scalings of north component (X), east component (Y), and vertical component (Z) 

of magnetic field intensity for 1 945 9 

4. Values of spherical harmonic coefficients, main field, 1C45 10 

5-7. Observed minus computed values of north component (X), east component (Y), and 

vertical component (Z), of magnetic field intensity for 1945 11 

8. Vertical air-earth currents computed from H- and D-charts of main field for 1945 and 

mean values 12 

9. The first eight Gauss coefficients of the Earth's magnetic potential (V) 13 

10-14. Computed values of north component (X) of magnetic field intensity for 1945 at heights 

100, 300, 500, 1000, and 5000 km 13 

15-19. Computed values of east component (Y) of magnetic field intensity for 1945 at heights 

100, 300, 500, 1000, and 5000 km 16 

20-24. Computed values of vertical component (Z) of magnetic field intensity for 1945 at 

heights 100, 300, 500, 1000, and 5000 km 18 

25. Computed values of magnetic potential (V), main field, for 1945 21 

26. Computed values of magnetic potential (V), residual field, for 1945 21 

27-29. Computed values of the vertical gradient of north component (3X/8r), east component 

(dY/dr), and vertical component (9Z/dr), of magnetic field intensity, main field for 1945 . 22 
30-32. Computed values of the vertical gradient of north component (dX/dr), east component 
(dY/8r), and vertical component (dZ/dr), of magnetic field intensity, residual field, 
for 1945 23 



Table 1. Scalings of values of north component (X) of magnetic field intensity for 1945 
expressed in units of 10-4 CGS from U. S. Hydrographic Office charts 



Geographic 
east 


Geographic colatitude in degrees 


longitude 


10 


20 


30 


40 


50 


60 


70 


80 


90 


in degrees 




















3 


67 4 


10 6 3 


15 4 


196 8 


2 52 9 


3 4 


3 4 


3 4 2 9 


309 3 


60 


50 2 


87 4 


14 13 


196 5 


2 5 9 9 


3 18 7 


3 62 


3 719 


3 4 2 3 


9 


27 


6 8 8 


129 7 


20 4 4 


2 8 5 9 


3 50 


3 9 3 8 


4 5 7 


3 85 4 


IPO 


27 8 


73 


1 4 4 8 


2 16 3 


2 8 R 5 


3 4 15 


3 77 


3 9 2 8 


3 R7 6 


ISO 


36 3 


10 15 


17? 2 


2 33 


2 7 5 9 


3 O 6 8 


3 310 


3 4 Q 3 


3 6 3 6 


18 


33 1 


1116 


1.838 


2 25 1 


2 4 6 9 


2*92 


2 917 


3 20 4 


34 6 1 


2 10 


17 4 


8 18 


1.438 


1 9 R 


2 3 1^ 


2 5R7 


2 8 7 


3 1 5 2 


3 317 


340 


17 


26 6 


9 4 


15 5 7 


2 2 1 


2 6 7 2 


30 16 


3 23 2 


3 2 3 7 


2 7 


R 2 


10 9 


5 5 4 


116 


18 6 5 


2/lM 


2 9 4 6 


3 17 6 


314 7 


3 


112 


4 13 


73 2 


1217 


1 70 7 


2 15 6 


2 55 8 


2 8 3 8 


295 3 


3 3 


4 4 4 


7*7 


114 8 


162 1 


2 8 6 


2 4 3 2 


2 6 8 4 


2 8 12 


2 70 


3 60 


6 9 2 


10 7 2 


14 14 


18 9 5 


2 3 8 4 


2 R R 1 


3 16 3 


3 12 5 


2 76 2 


Geographic 
east 








Geographic colatitude 


1 in degrees 








longitude 


100 


110 


120 


130 


140 


150 


160 


170 




in degrees 




















3 


2 4 4 2 


1 7R 9 


133 


123 5 


1316 


1307 


136 1 


3 4 5 




6 


2 8 14 


2 1 R 7 


163 4 


1 3 R 1 


130 6 


124 9 


10 40 


30 7 




9 


3 3 3 3 


266 1 


20 7 


14 80' 


113 9 


85 


3 8 9 


- 4 8 




12 


3 5 8 5 


317 8 


2 5 5 


1 R 4 8 


118 3 


6 10 


9 4 


8 9 




1 5 O 


3 5 9 2 


3 29 4 


2 7 5 5 


2 13 


14 2 


67 


8 7 


- 94 




1 R 


3 50 4 


3 26 7 


2 R 4 


2 3 3 7 


176 6 


10 3 5 


25 


- 6 10 




2 1 


3 30 5 


3 12 3 


2 R 3 9 


2 4 7 6 


2 4 9 


14 4 5 


69 


- 14 




2 4 


3 117 


2 96 9 


2 7 5 3 


2 5 3 3 


2 23 1 


176 9 


1110 


. 37 




2 70 


30 6 3 


2 77 6 


2 57 4 


2 4 3 


2 33 9 


2 115 


160 


10 3 8 




3 


2 R 3 


2 55 8 


2 36 


2 29 2 


2 35 4 


2 3 8 


2 7 


157 2 




3 3 


2 4 3 6 


2 10 


186 3 


1R5 


198 9 


2 10 5 


2 15 5 


185 




3 6 


2 2 6 5 


1 7 R 2 


1483 


14 1 


152 9 


162 3 


162 2 


164 1 





Table 2. Scalings of values of east component (Y) of magnetic field intensity for 1945 
expressed in units of 10-4 CGS from U. S. Hydrographic Office charts 



Geographic 
east 








G€ 


ographic colatitude 


in 


degrees 








longitude 


10 


20 


30 




40 


50 




60 


70 


80 


90 


in degrees 
























3 


9 2 


12 3 


13 9 




9 6 


7 9 




3 2 


3 


90 


2 5 


6 


29 1 


37 1 


36 8 




315 


24 1 




12 8 


3 2 


7 8 


- 22 1 


9 


26 7 


27 2 


24 3 




16 1 


5 5 


- 


3 7 


- 117 


- 15 6 


- 22 2 


12 


113 


12 


- 25 5 


- 


34 3 


- 29 3 


- 


18 5 


2 6 


117 


17 6 


15 


7 


- 17 4 


- 31 O 


- 


30 3 


- 25 1 


- 


10 7 


5 8 


214 


31 8 


1 8 


16 5 


17 7 


20 6 




29 2 


39 5 




45 5 


5 4 


54 2 


58 5 


2 ] 


20 7 


4 8 4 


67 5 




69 4 


74 3 




65 9 


5 8 9 


4 9 4 


53 7 


2 4 


9 9 


3 3 8 


59 1 




70 6 


7 3 2 




69 1 


62 5 


55 8 


53 


2 70 


- 16 


- 14 4 


- 13 3 




6 


13 




2 8 5 


37 7 


4 6 9 


52 1 


3 


- 4 3 6 


- 65 


- 65 2 


- 


69 2 


- 65 9 


- 


6 6 


- 52 


- 4 2 4 


- 316 


3 3 


- 4 3 2 


- 6 2 6 


- 67 1 


- 


73 5 


- 75 9 


- 


86 1 


- 98 8 


- 10 7 A 


- 1 5 8 


3 6 


- 16 1 


- 24 7 


- 27 5 




30 7 


- 35 6 




4 10 


- 4 8 4 


- 59 


- 70 4 


Geographic 
east 








Geographic 


: colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160. 


170 




3 


- 29 6 


- 38 4 


- 4 3 7 


_ 


5 4 9 


- 67 7 


_ 


92 2 


- 1 36 1 


- 1 6 4 




60 


- 38 1 


- 57 


- 75 5 


- 


93 9 


-1119 


- 


137 7 


- 1 6 5 2 


- 1 7 4 1 







- 33 3 


- 5 6 6 


- 77 


- 


10 6 


- 1 1 5 1 


- 


123 2 


- 1 3 6 6 


- 1 3 4 8 




12 


18 2 


117 





- 


20 7 


- 4 3 


- 


46 3 


- 4 4 2 


- 77 1 




1 5 


36 5 


4 16 


4 4 1 




4 14 


341 




26 9 


5 


3 




18 


6 3 


69 4 


719 




76 8 


77 9 




7 8 3 


7 6 


72 7 




2 10 


6 O 7 


6 9 8 


80 3 




8 8 7 


97 7 




1001 


10 11 


1140 




2 4 


57 8 


65 3 


77 4 




90 7 


10 5 9 




12 3 9 


1381 


15 6 




2 7 


5 9 5 


6 4 6 


74 8 




913 


10 6 6 




1 19 2 


134 7 


13 7 7 




3 0" 


- 20i 


8 9 


4 1 




19 2 


3 4 8 




52 8 


77 8 


7 4 6 




3 3 


9 6 4 


8 3 6 


- 70 


- 


5 R 3 


- 4 5 2 


- 


25 1 


- 10 5 


3 2 




3 6 


- 7 9 3 


- 8 16 


- 7 '8 9 


"■ 


75 1 


- 74 3 


— 


69 6 


- 82 5 


- 9 6 7 





Table 3. 



Scalings of values of vertical component (Z) of magnetic field intensity for 1945 
expressed in units of 10-4 CGS from U. S. Hydrographic Office charts 



Geographic 
east 








Geographic colatitude 


in degrees 








longitude 


10 


20 


30 


40 


50 


60 


70 


80 


90 


in degrees 




















3 


5 36 


5 110 


4 8 10 


4 3 7 


3 7 10 


2 79 


14 7 


P 


- 1 39 


6 o 


.5530 


5 4 6 


5 4 


4 9 4 


4 ?5 


3 2 6 


18 2 


37 


- 1 1 2 


q 


5 73 


5 8 4 


5 8 4 


5 4 4 


4 6 5 


34 2 


18 4 


16 


- 1 5 3 


1 2 o 


5 ? R n 


6 110 


5 9 3 0- 


5 43 


4 5P 


3 ? R 


187 


34 


-118 


15 


5 7 8 


5 72 


5 33 


4 5 R 


3 5 8 


2 62 


15 4 


4 6 


- 87 


IPO 


'5730 


5 510 


5 o n o 


4 18 


3 37 


2 55 


17 5 


8 4 


- 32 


P 1 


5 76 


5 6 4 


5 3P 


4 72 


3 94 


3 18 


2 27 


132 


14 


P 4 


5 79 


5 9 3 


5 9P 


5 56 


4 8 7 


3 9 6 


2 85 


163 


4 3 


P 70 


5 69 


5 R 1 


6 8 


5 9 80 


5 4 8 


4 6 8 


3 6 10 


2 35 


112 


3 


5 5 10 


5 5 9 


5 5 3 


5 3 8 


50 2 


4 4 10 


3 5 5 


2 5 8 


14 9 


3 3 


5 P 6 


5 1 3 


4 93 


4 62 


4 7 


3 22 


2 3 3 


13 30 


3 


3 6 


5 19 


5 10 


4 6 9 


4 27 


3 6 10 


2 7 10 


14 7 


8 


- 1 1 3 


Geographic 
east 








Geographic colatitude 


in degrees 








longitude 
in degrees 


100 


110 


120 


130 


140* 


150 


160 


170 




3 


- 2 33 


-2850 


- 2 9 8 


- 3 8 


- 3 30 


- 3 8 


- 4 7 3 


-5450 




60} 


- 3 33 


- 3 5 


- 3 26 


- 3 5 3 


- 3 76 


- 4 4 R 


- 5 3 2 


-5800 




9 i 


- 3 


- 4 4 


-4670 


- 5 2 0' 


-5150 


- 5 5 3 


- 5 9 8 


-6170 




1?0 


- 2 7 1 


-4060 


- 5 1 3 


- 5 8 5 


- 6 4 2 


- 6 5 1 


- 6 6 3 


-6530 




15 


- p 2 8 


- 3 67 


- 4 8 6 


- 5 7 6 


- 6 4 P 


- 6 8 5 


-6 97 


- 6 6 3 C 




1 8 


- l 6 n o 


- 3 3 


- 4 1 7 


- 50 7 


- 5 8 3 


- 6 5 4 


- 6 67 


-6560 




P 1 


- 1 1 2 


- 2 2 7 


- 3 36 


-4 ?8 


- 5 1 4 


-5 97 


- 6 P9 


-6370 




P 40 


- 67 


- 1 7 1 


-2670 


- 3 5 8 


- 4 4 3 


- 5 3 5 


- 5 6 3 


-5910 




270 


4 


- 1 7 


-18 7 


- 2 5 8 


- 3 33 


-4120 


-4 77 


-5470 




3 j 


44 


- 4 3 


- 1 7 


- 1 6 6 


- 2 36 


- 3 31 


-4 24 


-5180 




3 3 ( 
3 6 0j 


- 57 


- 1 1 R 


- 1 56 


- 1 8 8 


- 2 4 


-3110 


-4120 


-5110 




- 1 R 9 


— 2 P 9 


- 2 4 7 


- 2 6 3 


- 2 9 5 


- 3 37 


-4 27 


- 5 2 





Table 4. Values of spherical harmonic coefficients, main field, 1S45 
expressed in units of 10 _ 4 CGS 







A m 

A n 




n 


n m 


m 


m 


n 


















X 


Y 


Z 


X 


Y 


Z 




1 


- 3 5 7 






6114 










a 


- 25 3 






35 7 










4 


34 4 






- 42 7 










4 


36 8 






- 49 9 










b 


- 12 1 






19 2 










6 


3 4 






- 4 8 








1 


1 


- 19 


- 


? 3 


45 5 


57 7 


5 8 4 


-115 8 


1 


H 


59 4 




59 


- 882 


- 32 9 


- 33 4 


51 4 


1 


3 


- 510 


- 


52 7 


703 


- 15 4 


- 15 7 


187 


1 


4 


30 9 




313 


- 37 5 


70 


4 3 


5 8 


1 


b 


16 3 




116 


- 21 9 


12 


4 2 


5 


1 


6 


3 a 




8 7 


29 


1 


8 5 


3 2 


2 


3 


33 1 




32 2 


- 49 5 


12 4 


90 


- 142 


y 


3 


36 4 




36 2 


- 481 


6 1 


5 


82 


2 


4 


24 4 




217 


- 29 6 


- 10 3 


- 119 


146 


a 


5 


8 2 




115 


82 


4 7 


2 4 


5 2 


'<A 


6 


10 


- 


4 1 


3 5 


7 3 


10 3 


8 8 


3 


3 


P4 3 




28 2 


- 369 


1 7 




1 


3 


4 


- 15 3 


- 


15 1 


20 3 


4 1 


2 5 


5 2 


i 


,5 


3 5 


- 


2 5 


27 


8 


14 


1 


1 


6 


- 15 9 


- 


150 


170 


18 





13 


4 


4 


IP 3 




12 


- 14 6 


5 1 


5 1 


61 


4 


h 


7 1 


- 


7 4 


7 8 


6 3 


7 2 


77 


4 


6 


13 


- 


1 9 


19 


2 





4 


5 


5 


3 


_ 


3 8 


5 9 


2 6 


5 1 


5 5 


5 


h 


1 4 




2 2 


2 7 





9 


4 


6 


6 


60 


- 


69 


66 


3 5 


17 





10 



Table 5. Observed minus computed values of north component (X) of magnetic field intensity for 1945 

expressed in units of 10-4 CGS 



Geographic 
east 












Geographic colatitudf 


i in 


degrees 






longitude 




10 




20 


30 




40 


50 




60 


70 


80 


90 


in degrees 




























3 


_ 


115 


_ 


7 6 


1 2 




1 5 


3 


_ 


4 R 


4 3 


9 


3 5 


60 


- 


10 2 


- 


R 3 


1 




7 


5 


- 


2 3 


19 


4 


1 3 


90 


- 


10 5 


- 


4 1 


7 




2 B 


5 8 







2 4 


2 


3 3 


120 


- 


2 


- 


3 


3 4 


- 


1 


1 7 


- 


6 


7 


3 


2 


15 


- 


1 2 


- 


3 2 


2 9 


- 


1 5 


6 




1 4 


1 6 


2 


9 


1 BO 


- 


6 9 


- 


5 


1 7 




-R 


2 




3 4 


5 


40 


19 


2 10 


- 


5 R 


- 


3 9 


8 


- 


2 


2 7 


- 


2 6 


4 2 


6 


2 


2 4 


- 


1 1 


- 


9 9 


3 9 




6 9 


5 4 


- 


3 9 


6 


10 


2 9 


2 7 


- 


2 


- 


4 1 


2 




10 


1 8 


- 


2 7 


1 


1 5 


14 


3 


- 


4 7 




3 


6 




3 2 


10 


- 


2 6 


16 


1 3 


4 8 


3 3 


- 


6 7 


- 


40 







4 3 


3 9 


- 


1 9 


2 


4 2 


3 4 


3 6 




7 3 




2 3 


11 




2 5 


2 3 




7 


2 1 


3 6 


5 


Geographic 
east 












G€ 


ographic colatitude 


■ in 


degrees 






longitude 
in degrees 




100 




110 


120 


130 


140 


150 


160 


170 




3 


_ 


3 


_ 


3 6 


6 7 


_ 


8 


5 


_ 


14 


- 113 


- 22 




60 




1 




2 R 


3 4 


- 


4 1 


3 5 


- 


3 


2 9 


- 27 6 




9 




5 4 




4 5 


6 


- 


4 4 


2 2 




3 6 


3 


- 33 




IPO 


- 


2 4 




4 5 


4 3 




2 1 


1 4 




5 7 


15 


- 20 3 




15 




9 




2 4 


9 




2 4 


5 


- 


4 


3 4 


- 10 4 




ISO 




1 6 




2 9 


3 




3 5 


2 9 


- 


2 9 


6 


7 




2 10 




1 4 


- 


1 6 


2 7 


. - 


1 6 


4 2 




5 1 


2 3 


4 1 




2 4 




3 


- 


1 3 


4 7 




4 


7 5 




7 8 


4 7 


- 20 5 




2 70 




40 


- 


5 2 


5 6 


- 


4 4 


7 4 




7 2 


- 12 9 


- 25 2 




3 


- 


1 5 


- 


6 5 


5 7 


- 


1 


R 6 




12 


7 1 


- 25 




3 3 


- 


1 


- 


5 6 


5 7 




2 S 


100 




5 8 


2 3 


- 12 9 




3 60 


— 


3 5 


- 


4 9 


J> 




5 4 


9 8 


- 


2 8 


- 20 5 


- 117 





Table 6. Observed minus computed values of east component (Y) of magnetic field intensity for 1945 

expressed in units of 10~4 CGS 



Geographic 
east 








Geographic 


colatitude in 


degrees 










longitude 
in degrees 


10 




20 


30 


40 


50 


60 


70 


80 


90 


3 


1 2 


_ 


2 4 


6 


_ 


5 




7 - 


8 


2 1 


_ 


3 


20 


60 


3 9 


- 


5 1 


5 7 


- 


4 8 


- 


2 4- 


2 9 


16 


- 


1 2 


2 4 


90 


- 50 


- 


5 


3 9 


- 


4 1 


- 


5 2- 


5 8 


7 6 


- 


60 


4 8 


120 


4 


- 


8 2 


5 7 


- 


5 4 


- 


8 


5 


1 1 




1 


3 9 


15 


2 


- 


1 5 


5 1 




4 1 




10 - 


2 


6 




1 4 


2 7 


18 


1 




2 4 


1 3 




2 8 




5 


3 8 


3 




2 ] 


1 5 


210 


2 7 




7 


4 


- 


8 5 


- 


18 - 


2 


3 9 




2 


2 4 


2 4 


3 


- 


1 3 


30 




1 9 




1 1 


6 


8 


- 


1 


10 


2 70 


7 




2 8 


2 9 




2 




2 9 


5 6 


3 1 




3 5 


3 1 


3 


5 9 


- 


4 1 


2 4 




4 




10 - 


4 


1 3 


- 


2 6 


2 7 


3 3 


6 3 


- 


1 1 


1 2 




3 




5 


3 9 


1 


- 


3 1 


15 


3 60 


7 8 




3 2 


2 6 




10 




7 


5 


3 2 




4 2 


3 8 


Geographic 
east 








( 


Jeographic 


colatitude in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


11 


_ 


8 


3 1 




3 4 




6 2 


9 


- 23 8 


• 


37 9 




60 


3 3 


- 


5 


4 7 


- 


3 7 


- 


2 6- 


110 


- 24 4 


- 


24 2 




90 


3 7 


- 


6 7 


3 9 


- 


4 8 


- 


1 2 


2 2 


5 6 


- 


1 7 




120 


4 2 


- 


2 2 


1 6 


- 


3 


- 


1 3 


R 7 


23 2 


- 


17 




150 


1 7 




2 8 


2 6 


- 


1 


- 


2 5 


4 


R 6 




6 




180 


3 




7 


1 7 




2 




6 


1 8 


4 7 


- 


1 8 




2 10 


1 2 




2 


2 




3 3 




4 8- 


2 8 


- 14 


- 


12 




24 


9 




7 


1 2 







- 


1 1 


5 


2 




2 4 




2 70 


5 8 




41 


3 2 




4 6 




3 5 


1 9 


7 7 




5 9 




3 


2 


- 


2 


18 


- 


1 9 


- 


30 - 


1 3 


10 3 


- 


1 3 




3 3 


2 5 




5 6 


6 8 




40 




8 


3 5 


1 9 


- 


2 2 




3 60 


1 


- 


1 2 


7 


- 


2 


- 


1 7 


2 3 


- 100 


- 


23 4 





11 



Table 7. Observed minus computed values of vertical component (Z) of magnetic field intensity for 1945 

expressed in units of 10-4 CGS 



Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 



3 


- 


2 4 


5 5 


6 9 


11 - 


2 9 


4 ^ 


6 7 


6 7 


4 3 


60 


- 


?, R 


40 


1 R R 


9 3 


3 R 


4 R - 


2 9 


R 7 


R 9 


90 


- 


2 6 


1 5 


3 3 - 


1 2 - 


2 5 


3 3 - 


2 9 


5 2 


5 3 


1 P 


- 


P. 9 


10 5 


3 3 


1 3 


9 - 


1 2 - 


1 - 


7 


2 5 


1 5 


- 


R 8 


7 7- 


3 1 - 


16 - 


6 1 


7 - 


4 


2 6 


5 


1 ft 


- 


9 5 


R 4 


9 6 


1 


• 11 - 


7 2 - 


• 10 6 - 


5 3 


7 


sin 


- 


5 2 • 


4 2 


3 7 


3 - 


4 3 - 


15 - 


3 2 


4 7 


1 5 


2 4 


- 


1 3 


3 1 


4 5 


4 3 - 


117 


7 3 - 


6 


10 - 


1 5 


2 7 


- 


3 5 • 


7 2 


6 2 


3 7- 


2 7 


3 


6 4 


f, 9 


7 6 


3 


- 


5 7 


4 3 


5 


4 


R 


4 - 


3 1 - 


1 2 ■ 


3 4 


3 3 


- 


14 3 ■ 


2 3 


1 7 


4 9 


4 9 


1 6 


4 9 


6 2 


3 


3 60 


- 


13 6 


4 9 


4 9 


2 


?! 


R 4 


R 3 - 


1 7 


- 1 O 2 



Geographic 

east 

longitude 

in rlpgreps 



Geographic colatitude in degrees 



100 



110 



120 



130 



140 



150 



160 



170 



3 




1 2 




2 ft 


7 5 


3 4 


3 


- 


4 5 


_ 


27 R 


- 


20 7 


60 




2 f, 


- 


2 


12 3 


R 1 


19 2 


- 


n 


- 


22 6 


- 


17 8 


Q O 


- 


1 8 


- 


6 6- 


7 7 - 


3 3 


16 3 




113 


- 


5 1 


- 


115 


12 


- 


7 


- 


7 - 


2 7 


R - 


10 




5 3 


- 


2 8 


- 


12 2 


1 5 


- 


B 


- 


15- 


4 R • 


5 - 


R 


- 


12 5 


- 


1 /£ 


- 


5 7 


1 R 




2 1 


- 


3 - 


1 1 


7 - 


6 


- 


1 4 6 




<i 


- 


3 3 


210 


- 


4 2 


- 


2 9- 


4 


7 3 


R 2 


- 


7 


- 


£> 


- 


6 9 


2 4 


- 


3 3 


- 


6 2- 


5 


4 6 


5 R 


- 


16 1 




5 3 




2 7 


2 70 




2 6 


- 


' 4 1 


4 


7 2 


R 




4 7 




12 4 




4 2 


3 


- 


4 9 


- 


3 


7 7 


12 4 


9 5 


- 


4 4 


- 


3 2 


- 


3 


3 3 


- 


4 3 




5 


6 8 


10 7 


6 


- 


7 1 


- 


1 R R 


- 


14 1 


3 6 


- 


3 6 




6 8 


13 2 


9 6 - 


3 9 


- 


3 8 


- 


20 7 


- 


19 1 



Table 8(A). Vertical air -earth currents computed from H- and D-charts of main field for 1945 
expressed in milliamperes per kilometer squared 





Longitude east 


Latitude 


0° 
30° 


30° 
60° 


60° 
90° 


90° 
120° 


120° 
150° 


150° 
180° 


180° 
210° 


210° 
240° 


240° 
270° 


270° 
300° 


300° 
330° 


330° 
360° 



50°-40° N 


+ 6 


-39 


+ 7 


-60 


- 5 


+ 64 


+ 52 


+ 42 


- 1 


+ 27 


+ 70 


- 14 


40°-30° N 


+ 17 


-47 


+ 42 


+ 3 


+ 6 


+ 3 


+ 10 


- 7 


-52 


+ 60 


-53 


- 55 


30°-20° N 


-77 


-37 


+ 8 


-15 


+ 49 


-55 


-39 


+ 80 


- 9 


- 6 


-59 


- 48 


20°-10° N 


-24 


+ 73 


- 62 


+ 9 


- 9 


-12 


-12 


+ 43 


+ 52 


-20 


-27 


- 95 


10°- 0° N 


-49 


+ 79 


- 37 


- 3 


+ 7 


- 1 


-12 


- 3 


+ 19 


-19 


+ 18 


-100 


0°-10° S 


-97 


- 6 


+ 16 


+ 4 


-46 


- 9 


+ 12 


+ 33 


- 1 


-33 


+ 12 


+ 25 


10°-20° S 


-21 


-60 


+ 53 


-41 


+ 17 


- 2 


-43 


+ 33 


-47 


+ 9 


+ 62 


+ 121 


20°-30° S 


+ 17 


+ 77 


+ 150 


+ 57 





+ 35 


-59 


+ 13 


-90 


+ 28 


+ 31 


+ 97 


30°-40° S 


-48 


+ 27 


+ 100 


+ 66 





-80 


-70 


-43 


-67 


+ 29 


+ 10 


+ 9 



Table 8(B). Mean values of vertical air -earth currents 



Epoch 



America 



'Zone' 



Eurasia 



1/2 Span 



General 
mean 



1885 
1922 
1945 



+ 36.7 


+ 26.7 


-81.6 


+ 59.2 


-15.2 


+ 20.2 


-30.1 


-35.0 


+ 27.6 


-11.2 


- 0.6 


- 6.5 


+ 2.4 


+ 0.9 


- 0.3 



12 



Table 9. The first eight Gauss coefficients of the Earth's magnetic potential (V) 
expressed in units of 10"4 CGS 



Source 


Epoch 



*1 


1 
Si 


>,' 




s 2 


1 
g 2 


*.' 


2 
&2 


h 2 


Gauss 


1835 


-3235 


-311 


+ 625 


+ 51 


+ 292 


+ 12 


- 2 


+ 157 


Er man-Peter sen 


1829 


-3201 


-284 


+ 601 


- 8 


+ 257 


- 4 


- 14 


+ 146 


Adams 


1845 


-3219 


-278 


+ 578 


+ 9 


+ 284 


- 10 


+ 4 


+ 135 


Adams 


1880 


-3168 


-243 


+ 603 


- 49 


+ 297 


- 75 


+ 61 


+ 149 


Fritsche 


1885 


-3164 


-241 


+ 591 


- 35 


+ 286 


- 75 


+ 68 


+ 142 


Schmidt 


1885 


-3168 


-222 


+ 595 


- 50 


+ 278 


- 71 


+ 65 


+ 149 


Dyson and Furner 


1922 


-3095 


-226 


+ 592 


- 89 


+ 299 


-124 


+ 144 


+ 84 


Afanasieva (8) 


1945 


-3032 


-229 


+ 590 


-125 


+ 288 


-146 


+ 150 


+ 48 


Vestine and Lange 


1945 


. -3057 


-211 


+ 581 


-127 


+ 296 


-166 


+ 164 


+ 54 



Table 10. Computed values of north component (X) of magnetic field intensity for 1945 at height 100 km 

expressed in units of 10-4 CGS 



Geographic 
east 








Geographi 


c colatitude 


in degrees 






longitude 


10 


20 


30 


40 


50 


60 


70 


80 


90 


in degrees 




















3 


74 8 


109 3 


14 4 1 


18 8 1 


2 4 17 


2 9 3 7 


3 26 4 


3 25 8 


2 90 9 


60 


5 8 4 


92 7 


135 7 


18 8 5 


2 4 8 4 


30 5 7 


345 3 


3 52 9 


3 24 1 


9 


37 9 


72 2 


125 4 


19 3 6 


2 67 1 


3 32 2 


3 75 3 


3 86 1 


362 6 


120 


30 9 


7'5 1 


136 7 


20 6 9 


2 73 1 


3 25 3 


3 59 


373 6 


36 8 5 


15 


37 6 


J009 


167 1 


2 23 2 


2 63 7 


2 9 18 


3 149 


3 35 2 


3 4 7 


180 


39 1 


1110 


172 9 


2 13 6 


2 36 6 


2 5 5 3 


2 8 4 


30 9 8 


3 312 


a i o 


22 9 


82 


137 


182 3 


2 18 7 


2 5O0 


2 7 8 3 


30 14 


3 14 3 


2 4 


3 


36 4 


84 1 


14 2 7 


2 4 6 


2 5 7 5 


2 92 2 


306 7 


30 6 


2 70 


5 2 


16 2 


5 4 8 


1111 


176 3 


2 36 5 


2 79 6 


30O3 


30 10 


3 


15 2 


37 7 


70 9 


114 5 


162 8 


2 8 5 


2 4 5 5 


2 69 1 


2 76 8 


3 3 


4 8 o 


77 4 


110 6 


1516 


19 5 7 


2 33 7 


2 57 5 


2 64 1 


2 54 6 


3 60 


72 


10 4 9 


137 4 


179 8 


2 29 9 


2 74 5 


2 9 8 2 


2 9 3 4 


2 6 3 9 




Geographic 
east 








Geographi 


: colatitude 


in degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 o 


2 34 4 


177 


136 8 


12 15 


126 4 


137 5 


13B5 


1180 




60 


2 6 9 


2 8 4 


162 


13 7 7 


12 8 2 


1181 


9 4 5 


53 8 




9 O 


3 12 5 


2 50 8 


192 8 


14 7 


1115 


77 4 


36 1 


- 14 8 




13 


3^3 


2 9 8 


2 39 


17 4 7 


112 2 


53 3 


6,9 


- 64 8 




1 5 


3 4 5 


3 10 8 


2 6 13 


20 8 


135 9 


6 7 8 


4 7 


- 7 8 4 




1 8 


3 3 1 S 


3 8 


2 6 7 8 


2 1. 9 5 


1 6 5 2 


10 9 


24 5 


- 56 1 




2 10 


3 13 6 


2 9 9 1 


2 7 3 1 


2 37 3 


19 8 


13 2 5 


6 3 8 


8 2 




2 4 


2 97 6 


2 8 4 8 


2 67 1 


2 4 11 


20 5 4 


1613 


110 6 


55 5 




2 7 


2 R 8 7 


2 70 7 


2 5 19 


2 34 3 


2 16 4 


194 6 


164 3 


122 4 




3 


2 6 O 


2 511 


2 32 1 


2 20 3 


2 16 9 


2 14 9 


20 2 5 


1717 




3 3 


2 33 5 


20 7 5 


185 6 


17 6 1 


1816 


194 9 


2 13 


I86 




3 60 


2 20 7 


177] 


14 4 8 


1315 


138 5 


157 6 


1 72 5 


164 7 





13 



Table 11. Computed values of north component (X) of magnetic field intensity for 1945 at height 300 km 

expressed in units of 10-4 CGS 



Geographic 
east 








Geographic colatitude 


in degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


67 6 


10 9 


134 2 


174 5 


2 217 


266 5 2943 


2 93 7 


2 6 4 


60 


54 6 


87 1 


127 


174 9 


2 2 R 


2779 3118 


3 18 2 


29 3 5 


90 


3 8 


70 p. 


1 1 R 3 


178 8 


24 3 4 


3004 3379 


347 6 


3 27 5 


12 


32 3 


72 9 


127 7 


189 8 


2 4 8 3 


2949 32 5 2 


3 38 3 


3 33 6 


15 


37 3 


93 8 


152 5 


20 2 9 


2 40 3 


2 6 6 9 2 8 8 2 


30 6 


3 15 3 


180 


37 3 


1 O 1 


15 6 3 


194 2 


2 17 2 


2357 2 5 83 


2 3 3 


3007 


2 10 


22 1 


75 3 


12 4 9 


16 6 5 


2 3 


2292 2 5 48 


2 75 1 


2 R 6 4 


2 4 


1 9 


35 7 


79 2 


1315 


18 6 1 


2331 2645 


2 7 8 6 


2 7 9 2 


2 70 


3 5- 


18 


53 6 


10 3 8 


16 11 


2141 25 2 4 


2 717 


2 7 3 6 


3 


13 8 


36 2 


67 3 


10 6 9 


15 1 


1909 2237 


2 4 4 8 


2 519 


3 3 


4 2 5 


713 


10 2 7 


14 


179 2 


2129 2342 


2 4 5 


2 32 8 


3 60 


64 1 


96 3 


127 6 


166 2 


2 10 2 


24R7 2693 


2 65 6 


2 40 5 




Geographic 
east 








Geographic colatitude 


in degrees 






longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


215 8 


166 3 


1 30 8 


115 8 


117 4 


1243 1228 


10 3 




60 


2 4 6 4 


194 


152 7 


129 1 


117 6 


10 5 7 82 9 


4 6 




9 


2 8 4 3 


2 30 6 


179 


136 9 


10 2 9 


70 2 318 


- 14 2 




12 


3 10 5 


2 70 3 


2 17 6 


159 9 


10 3 3 


4 9 4 - 3 7 


- 57 7 




15 


30 R 4 


2 815 


2 37 3 


18 2 9 


124 


6 19 - 3 5 


- 69 1 




1 BO 


30 3 


2 79 5 


2 4 3 8 


199 9 


149 9 


9 11 22 7 


- 4 8 5 




2 10 


2 R5 4 


2 72 3 


2 4 R 5 


2 15 5 


17 3 


120 2 5 R 8 


5 2 




2 4 


2 72 


2 6 4 


2 4 3 6 


2 19 5 


187 1 


1471 1014 


518 




2 7 


2 63 8 


2 4 9 


2 316 


2 15 1 


19 8 


1772 1^89 


1107 




3 


2 45 7 


2 30 6 


2 14 4 


20 3 4 


19 8 8 


1948 1818 


1 53 3 




3 30 


2 14 7 


192 4 


17 3 4 


16 4 6 


167 9 


1772 1803 


164 9 




3 60 


2 3 5 


16 3 5 


137 4 


125 


129 5 


1439 1541 


14 5 2 




Table U 


. Compute 


d values of north component (X) of magnetic 
expressed in units of 10-4 


field intensity for 1945 at height 500 km 
CGS 


Geographic 
east 








Geographic colatitude 


in degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


6 14 


9 3 2, 


124 9 


16 18 


20 3 7 


3426 2664 


2 6 5 8 


2 4 4 


60 


511 


819 


118 8 


162 3 


2 9 6 


2533 2826 


2 8 8 


2 66 8 


9 


37 6 


67 9 


1115 


165 5 


2 22 5 


2724 3055 


3 14 


2 9 6 8 


12 


33 


70 3 


119 4 


17 4 5 


3 26 5 


2 6 8 2 2 9 5 5 


307 3 


302 9 


15 


36 6 


87 3 


139 6 


1 8 5 1 


2 19 5 


2446 2643 


2 79 9 


2 87 3 


180 


35 4 


92 2 


14 19 


177 2 


199 7 


2178 2382 


2 59 7 


2 74 


2 10 


213 


69 2 


114 2 


1 5 2 5 


18 3 9 


2106 2338 


2 5 19 


2 6 16 


24 


30 


34 8 


74 4 


1213 


169 9 


3117 2403 


2 53 8 


2 5 5 3 


2 70 


2 2 


19 


519 


9 6 8 


147 6 


1944 2289 


2 4 6 7 


2 4 9 5 


3 


12 6 


34 6 


63 7 


99 7 


13 8 6 


1751 204 5 


2 23 4 


2 30 


3 3 


37 8 


65 7 


95 4 


129 3 


16 4 5 


194 4 2 13 7 


2 19 7 


2 13 3 


3 60 


5 7 4 


8 8 5 


1 1 R 5 


153 7 


192 6 


2262 2442 


2 4 13 


2 2 




Geographic 
east 








Geographic 


: colatitude 


in degrees 






longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


199 


15 6 2 


124 6 


1 1 


10 9 3 


112 9 10 9 5 


90 5 




60 


2 2 6 2 


1 R 6 


14 3 6 


1209 


1 O R 1 


95 1 73 2 


39 5 




90 


2 59 4 


2 12 3 


16 6 3 


12 7 5 


95 2 


6 4 2 8 2 


- 13 6 




12 


2 R 2 1 


2 4 5 9 


1 9 R 8 


14 6 9 


9 5 4 


4 6 - 2 6 


- 515 




15 


2 R 3 


2 5 5 R 


2 16 1 


16 7 


113 4 


5 6 8 - 2 3 


- 610 




1 R 


2 73 


2 5 4 4 


2 22 4 


18 2 5 


13 6 5 


82 8 212 


- 4 2 1 




2 10 


2 6 6 


2 4 R 5 


2 26 8 


19 6 4 


157 4 


10 9 4 54 2 


2 7 




2 4 


2 4 9 3 


2 3R 6 


2 22 9 


20 O 6 


170 9 


134 6 93 2 


4 8 4 




2 7 


2 4 16 


2 2 R 3 


2 13 2 


197 9 


18 16 


16 18 13 5 4 


10 5 




3 


2 2 5 


2 12 3 


19 8 2 


18 8 1 


182 7 


1772 1639 


137 5 




3 3 


197 9 


1 7 R 7 


1 62 1 


153 9 


15 5 4 


16 16 162 1 


14 6 9 




3 6 


1 8 R O 


1 5 5 2 


130 1 


118 6 


12 11 


1317 1384 


128 7 





14 



Table 13. Computed values of north component (X) of magnetic field intensity for 1945 at height 1000 km 

expressed in units of 10-4 CGS 



Geographic 
east 






Geographic 


colatitude 


in degrees 




longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


4 9 77 


10 4 5 


134 4 


166 1 


194 2 


2109 210 5 1929 


6 


4 3 5 70 


10 6 


13 5 1 


1711 


2 3 2 


2242 2279 2130 


90 


35 4 613 


95 9 


13 7 1 


179 7 


2 16 6 


2 4 9 2 4 7 5 2 3 5 5 


120 


32 4 63 


10 11 


14 2 8 


182 3 


2 14 3 


23 5 6 2448 2411 


150 


33 7 73 2 


113 5 


14 9 2 


177 4 


19 8 6 


2147 2262 2304 


180 


30 8 74 4 


113 2 


14 2 6 


16 3 2 


179 7 


1959 2109 2200 


210 


18 8 56 7 


92 5 


123 7 


149 8 


1718 


1903 2040 2111 


24 


4 5 3 12 


6 3 6 


10 


136 9 


169 


1917 2036 2062 


2 70 


1 19 6 


4 6 8 


817 


119 9 


1 5 5 2 


1.8 1. 8 1967 2004 


3 


10 30 5 


55 2 


84 


114 3 


14 2 5 


1652 1799 18 5 5 


3 3 


28 8 53 8 


79 3 


10 6 7 


134 


157 


1720 1774 173 5 


3 60 


4 4 3 72 2 


98 5 


126 9 


156 2 


180 7 


1940 1926 1780 




Geographic 
east 






Geographic 


colatitude 


in degrees 




longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


1640 1332 


10 9 3 


96 1 


918 


90 2 


8 3 8 6 6 8 


60 


1843 1513 


122 8 


10 2 7 


88 7 


74 6 


55 27 7 


90 


2087 1739 


138 7 


10 7 


79 


5 17 


217 - 118 


12 


2247 1967 


160 4 


119 8 


78 8 


3 8 8 


5-393 


150 


2237 2040 


173 1 


134 5 


918 


4 6 5 


0-454 


180 


2181 203 5 


17 8 8 


14 6 9 


10 9 5 


66 3 


18 3 - 29 8 


210 


2099 2001 


182 4 


157 7 


126 1 


8 8 


4 5 1 14 


2 4 


2023 1937 


180 5 


162 1 


138 1 


10 9 1 


76 3 4 11 


?! 7 


19 5 9 18 6 6 


174 9 


162 2 


147 9 


130 5 


10 8 2 80 1 


3 


1827 1742 


164 


15 5 5 


14 9 1 


14 17 


12R7 1067 


3 3 


1629 1493 


137 2 


130 1 


12 8 9 


129 9 


126 5 1123 


3 60 


15 55 1318 


113 2 


10 3 4 


10 2 7 


10 6 7 


1 7 6 9 7 1 


Table 14 


. Computed values of north component (X) of 


magnetic field intensity for 1945 at height 5000 km 


• 




expre 


ssed in units of 10-* CGS 




Geographic 
east 






Geographic 


colatitude 


in degrees 




longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


12 9 22 


30 6 


3 8 4 


4 5 1 


5 2 


531 536 517 


60 


14 4 22 9 


31 5 


39 6 


4 7 


52 8 


5 63 571 553 


9 


147 2 3 


31 7 


4 4 


4 8 4 


54 9 


591 60 5 5R9 


120 


14 3 23 


32 1 


4 10 


49 


55 4 


597 615 605 


ISO 


12 9 22 7 


32 1 


4 7 


4 5 2 


53 8 


578 599 5 97 


18 


10 3 20 5 


30 


3 8 4 


45 3 


50 8 


549 574 580 


210 


6 4 16 1 


25 4 


34 


4 14 


4 7 5 


5 22 55 2 564 


24 


2 6 113 


2 1 


28 9 


37 


4 4 1 


497 533 55 


2 70 


9 8 7 


16 9 


25 3 


33 5 


4 8 


468 509 531 


3 


2 1 101 


18 


25 7 


33 1 


39 5 


448 4 8 5 50 5 


3 3 


5 7 14 4 


22 6 


30 2 


36 8 


42 3 


461 483 4R8 


3 60 


9 9 19 1 


27 6 


35 3 


4 18 


4 6 6 


497 50 5 493 




Geographic 
east 






Geographic 


colatitude 


in degrees 




longitude 


100 


110 


120 


130 


140 


150 


160 


170 




in degrees 




















3 


47 9 4 3 1 


38 1 


33 3 


28 8 


24 


186 119 


60 


512 4 5 6 


39 3 


3 2 8 


26 2 


19 3 


118 3 8 


90 


5 4 7 4 8 4 


4 9 


32 6 


23 9 


15 1 


5 9 - 3 2 


12 


5 6 9 5 8 


42 9 


33 6 


23 5 


13 1 


2 7 - 7 2 


15 


5 7 1 5 2 


4 4 8 


35 7 


2 5 4 


14 5 


3 5 - 6 9 


18 


5 6 4 5 2 5 


4 6 5 


3 8 6 


29 2 


1 R 8 


8 - 2 4 


2 10 


5 5 6 5 2 9 


4 8 1 


417 


33 7 


24 5 


14 8 5 


2 4 


5 4 8 5 2 9 


4 9 3 


4 4 3 


3 8 


30 5 


22 3 13 6 


2 70 


5 3 5 5 2 3 


4 9 7 


4 6 


4 13 


3 5 5 


2 8 6 2 8 


3 


5 10 5 1 


4 8 1 


4 5 3 


4 17 


37 2 


316 2 4 7 


3 30 


4 7 9 4 6 1 


4 3 7 


4 1 O 


3 R 1 


34 6 


30 1 ?4 


3 6 


4 6 6 4 3 1 


39 4 


3 6 


32 8 


2 9 3 


2 5 1 19 3 



15 



Table 15. 



Computed values of east component (Y) of magnetic field intensity for 1945 at height 100 km 
expressed in units of 10-4 CGS 



Geographic 
east 








Geographic colatitude 


in degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


R 2 


12 4 


115 




R 7 




5 9 


2 7 


2 


9 3 


- 1 R 5 


6 


2 9 2 


37 R 


3 R 4 




32 8 




2 4 


14 1 


3 9 


6 


- 19 1 


9 


2 ft 5 


2 R R 


25 2 




18 1 




9 6 


1 8 


4 


9 2 


- 16 6 


13 


14 2 


3 2 


- 17 R 


- 


26 


- 


25 7 


- 17 


3 2 


114 


19 4 


150 


7 4 


- 13 3 


- 27 2 


- 


30 3 


- 


2 2 R 


R 6 


6 7 


17 4 


27 9 


1 ft 


15 7 


15 6 


19 2 




25 7 




33 


39 7 


4 5 


4 9 5 


54 2 


210 


23 


4 5 2 


63 7 




72 9 




715 


62 7 


52 9 


4 7 8 


49 R 


2 4 


9 9 


33 3 


52 6 




64 3 




67 6 


64 5 


5 R 6 


53 5 


519 


270 


- 20 6 


- 15 3 


9 


- 


6 




9 R 


216 


32 4 


4 5 


4 6 


3 


- 45 8 


- 5 6 5 


- 6 2 8 


- 


6 4 8 


- 


6 2 4 


- 56 3 


- 4 7 6 


- 37 6 


- 27 5 


3 30 


- 4 6 6 


- 57 9 


- 64 6 


- 


69 8 


- 


7 6 6 


- 8 4 9 


- 93 


- 9 R 


- 9 P 


3 60 


- 23 3 


- 27 


- 29 2 


- 


3 9 


- 


34 1 


_ 4 3 


- 4 9 6 


- 611 


- 6 9 5 




Geographic 
east 








Geographic colatitude 


in degrees 








longitude 


100 


110 


120 




130 




140 


150 


160 


170 




in degrees 
























3 


2 R 


- 3 6 R 


- 4 5 6 


_ 


56 5 


_ 


711 


- R 8 8 


-10 6 3 


- 1 1 R 9 




60 


- 33 3 


- 4 9 4 


- 67 


- 


85 1 


- 


10 2 8 


- 1 1 9 


-1321 


- 1 40 5 




q o 


- 2 R 9 


- 4 6 7 


- 6 R 1 


- 


89 1 


- 


1 5 R 


- 1 16 6 


-122 1 


- 1 2 4 2 




13 


2 2 


12 4 


18 


- 


19 1 


- 


36 2 


- 510 


- 62 4 


- 6 9 R 




1 5 


33 3 


37 


39 4 




39 2 




34 5 


25 2 


13 4 


3 3 




1 ft 


59 6 


6 5 1 


69 R 




7 2 6 




73 4 


72 7 


7 17 


709 




sin 


57 1 


66 4 


7 4 6 




Rl 5 




R R 7 


9 R 


10 9 2 


1. 1 9 




2 4 O 


54 R 


62 


72 R 




R 6 2 




10 13 


116 4 


1 29 R 


13 9 2 




P. 7 


50 6 


57 1 


67 4 




Rl 3 




96 3 


10 9 4 


1 1 R 3 


122 9 




3 


- 17 4 


6 9 


5 1 




19 2 




34 7 


4 9 8 


62 2 


70 




3 3 


- 92 9 


- R4 


- 72 3 


- 


5 R 8 


- 


4 3 6 


- 27 4 


- 12 5 


2 1 




3 60 


- 75 


- 76 3 


- 74 3 


- 


714 


- 


6 9 2 


- 6 R 6 


- 6 9 1 


- 69 8 




Table 1 


6. Computed values of east component (Y) of magnetic field intensity for 1945 at height 300 km 








expr 


essed in un 


its 


of 10-4 


CGS 






• 


Geographic 
east 








Geographic colatitude 


in degrees 








longitude 


10 


20 


30 




40 




50 


60 


70 


80 


90 


in degrees 
























30 


4 6 


R 7 


R 3 




6 2 




3 6 


6 


3 8 


- 10 4 


- 18 5 


60 


22 R 


30 4 


313 




26 9 




19 7 


113 


2 4 


-. "7 1 


- 18 


90 


23 1 


23 3 


20 4 




14 6 




7 7 


1 3 


3 7 


R 5 


- 15 1 


ISO 


12 5 


2 2 


- 14 4 


- 


212 


- 


20 9 


- 1 3 R 


2 4 


R fl 


16 1 


15 


R 1 


9 2 


- 20 7 


- 


23 3 


- 


17 2 


5 6 


7 3 


1 R 2 


25 7 


1 BO 


16 


15 9 


1 R 9 




24 2 




30 4 


36 1 


4 7 


4 4 9 


4 9 1 


2 10 


22 1 


4 7 


56 2 




64 2 




63 4 


56 7 


4 9 


4 5 


46 6 


2 4 


10 4 


30 1 


4 6 3 




5 6 5 




59 6 


57 5 


53 


4 9 1 


4 8 


2 70 


- 16 6 


- 12 2 


6 7 




3 




9 3 


19 2 


2 8 4 


35 5 


4 6 


3 


- 39 5 


- 4 R R 


- 54 4 


- 


56 4 


- 


5 4 6 


- 4 9 5 


- 42 3 


- 33 7 


- 25 


3 3 


- 4 14 


- 515 


- 57 7 


- 


6 2 9 


- 


6 r a 


- 75 9 


- R2 6 


- 86 7 


- R6 7 


3 6 


- 22 2 


- 25 4 


- 27 5 


- 


29 3 


- 


32 4 


- 37 9 


- 4 6 8 


- 55 


- 62 8 




Geographic 
east 








Geographic 


: colatitude 


in degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


- 26 9 


- 34 9 


- 4 3 1 


- 


53 


_ 


65 3 


- 80 8 


- 95 5 


-106 1 




60 


- 30 5 


- 4 4 7 


- 6 1 


- 


75 9 


- 


914 


- 1 5 5 


- 1 16 8 


- 1 24 1 




90 


- 25 9 


- 4 13 


- 59 4 


- 


77 3 


- 


9 1 R 


- 10 1 4 


- 1 6 5 


- 10 8 6 




12 


16 5 


9 9 


2 1 


- 


1 6 R 


- 


31 4 


- 4 4 1 


- 5 3 8 


- 600 




15 


30 5 


33 7 


35 6 




35 




30 8 


22 9 


13 


4 6 




i ao 


53 9 


5R 8 


62 9 




6 5 5 




66 3 


66 


65 2 


64 5 




2 10 


52 8 


6 7 


6 R 




74 3 




80 9 


89 1 


9 8 5 


10 6 5 




24 


50 7 


57 1 


66 5 




7 R 1 




910 


10 3 9 


115 2 


123 1 




2 70 


4 4 9 


50 9 


59 9 




717 




8 4 4 


95 5 


103 3 


10 7 4 




3 


- 16 2 


6 R 


3 7 




16 




29 4 


4 2 4 


53 1 


59 9 




3 3 


- 82 3 


- 74 6 


- 64 5 


- 


52 6 


- 


39 3 


- 25 4 


- 12 8 


3 9 




3 60 


- 67 6 


- 6 R f 


- 67 3 


— 


65 


- 


6 3 1 


- 62 5 


- 62 8 


- 63 5 





16 



Table 17. Computed values of east component (Y) of magnetic field intensity for 1945 at height 500 km 

expressed in units of 10-4 CGS 



Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 


10 


20 


30 




40 




50 




60 


70 


80 


90 


in degrees 


























3 


1 8 


5 7 


5 7 




A 




1 8 


_ 


1 


5 2 


- Ill 


- 1R 2 


60 


17 7 


24 5 


2 5 5 




22 2 




16 1 




8 9 


1 1 


7 3 


- 17 


90 


1 R 8 


19 


1. 6 5 




1 1 R 




6 2 




8 


3 5 


7 8 


- 13 9 


1 ?! O 


111 


14 


- 116 


- 


17 3 


- 


17 


- 


111 


18 


7 5 


13 4 


1 5 


R 6 


5 8 


- 15 6 


- 


17 9 


- 


12 9 


- 


3 2 


7 7 


17 


23 6 


] R 


16 


16 


1 R 5 




22 9 




2 8 




32 9 


37 1 


4 8 


4 4 7 


2 10 


2 1?, 


3 6 8 


4 9 9 




5*8 




56 6 




5 14 


4 5 3 


4 2 2 


4 3 6 


3 4 


1 O 6 


27 3 


4 1 1 




4 9 9 




52 9 




515 


4 8 


4 5 3. 


4 4 5 


2 70 


- 13 5 


9 7 


4 9 




1 1 




8 7 




17 2 


25 1 


313 


3 6 


3 


- 34 3 


- 4 2 4 


- 4 7 5 


- 


4 9 2 


- 


4 7 9 


- 


4 3 R 


- 37 6 


- 30 3 


- 22 7 


3 3 


3 7 


- ■* 6 


- 519 


- 


56 7 


- 


6 2 


- 


6 R 1 


- 7 3 7 


- 77 1 


- 77 


3 6 


- 211 


- 2 3 9 


- 2 5 9 


- 


27 7 


- 


30 6 


- 


35 6 


- 4 2 6 


- 6O3 


- 57 




Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


- 25 R 


- 33 1 


- 4 6 


_ 


4 9 6 


_ 


6 8 


_ 


73 7 


- 8 6 2 


- 95 1 




60 


- 2 R 1 


- 4 6 


- 54 1 


- 


6 R 


- 


fll 6 


- 


93 9 


- 1 3 7 


-1100 




00 


- 23 3 


- 36 6 


- 52 2 


- 


67 6 


- 


80 1 


- 


8 R 7 


- 93 4 


- 95 3 




12 


13 6 


7 9 


2 3 


- 


14 8 


- 


27 3 


- 


3 8 2 


- A f, f, 


- 5 18 




ISO 


2 R 


30 8 


32 2 




315 




27 7 




20 9 


12 7 


5 7 




18 


4 8 9 


5 3 3 


56 9 




59 3 




6 2 




60 


50 4 


5 8 9 




2 10 


4 R 9 


55 6 


62 1 




67 9 




73 9 




Rl 1 


8 9 1 


95 7 




2 4 


4 7 


52 6 


6 8 




7 9 




82 




9 3 1 


10 2 7 


10 9 4 




2 7 C 


4 1 


4 5 5 


5 3 4 




6 3 S 




74 3 




8 3 8 


9 6 


9 4 3 




3 


- 14 9 


6 6 


2 7 




1 3 5 




25 1 




36 2 


4 6 5 


515 




3 3 


- 73 3 


- 6 6 6 


- 57 7 


- 


47 3 


- 


3 5 7 


- 


23 6 


- 12 8 


5 2 




3 60 


- 611 


- 62 3 


- 6 12 


- 


59 3 


- 


57 7 


- 


57 2 


- 57 4 


- 57 9 





Table 18. Computed values of east component (Y) of magnetic field intensity for 1945 at height 1000 km 

expressed in units of 10-4 CGS 



Geographic 
east 








Geographi 


c colatitude in 


degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


2 6 


f, 


1 1 




2 


14 


_ 


3 8 


7 2 


- 117 


- 17 2 


6 


9 1 


14 1 


15 3 




13 5 


9 6 




4 6 


10 


7 3 


- 14 7 


9 


116 


116 


100 




7 1 


3 5 







3 1 


6 5 


- 113 


12 


8 6 


1 


6 7 


- 


10 4 


- 10 3 


- 


6 6 


7 


5 1 


8 7 


1 5 


9 1 


5 


6 9 


- 


R 6 


5 5 




7 


8 


14 5 


19 4 


1 RO 


15 3 


15 3 


16 9 




1 9 R 


23 3 




26 7 


29 8 


32 7 


35 8 


2 10 


18 7 


2 9 2 


3 R 1 




4 3 


4 3 5 




4 8 


37 5 


35 R 


36 9 


2 4 


10 3 


217 


312 




37 5 


4 1 




39 8 


3 R 1 


36 8 


36 8 


2 7 


R 1 


5 4 


2 1 




2 1 


7 4 




13 2 


1 8 8 


2 3 4 


27 1 


3 


- 24 8 


- 30 7 


- 34 5 


- 


3 6 


- 35 3 


- 


32 7 


- 2 8 6 


- 2 3 5 


- 18 


3 3 


- 2 8 6 


- 35 4 


- 4 3 


- 


4 4 3 


- 4 8 3 


- 


52 6 


- 5 6 4 


- 5 8 6 


- 5 8 4 


3 60 


- 18 6 


- 20 6 


- 22 3 


- 


2 4 


- 2 6 5 


- 


30 3 


- 35 3 


- 4 6 


- 4 5 2 




Geographic 
east 








Geograph 


ic colatitudi 


2 in degree 


s 






longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


- 23 


- 2 8 8 


- 34 8 


_ 


4 18 


- 50 


_ 


59 


- 67 5 


- 73 6 




60 


- 23 


- 32 3 


- 42 3 


_ 


52 5 


- 6 2 4 


- 


71 3 


- 78 4 


- 83 




90 


- 18 2 


- 27 6 


- 38 6 


_ 


4 9 3 


- 58 3 


- 


64 7 


- 6 8 5 


- 7 2 




1 2 


8 6 


4 7 


2 3 


_ 


10 8 


- 19 5 


- 


27 1 


- 32 9 


- 36 5 




1 5 


22 6 


24 6 


25 4 




2 4 6 


218 




17 1 


117 


7 2 




18 


39 


4 2 2 


45 




4 6 9 


4 7 8 




47 9 


47 7 


47 3 




2 10 


4 6 


4 5 2 


5 1 




54 7 


59 4 




6 4 6 


70 1 


74 4 




24 


3 8 9 


4 3 1 


4 9 1 




56 3 


64 1 




719 


7 8 4 


82 9 




2 70 


30 6 


35 


4 7 




4 7 8 


55 2 




618 


66 6 


6 9 4 




3 


- 12 3 


60 


9 




8 7 


17 




24 9 


315 


35 9 




3 3 


- 55 7 


- 50 9 


- 4 4 5 


- 


36 8 


- 2 8 5 


- 


19 9 


- 12 4 


7 1 




3 60 


- 4 8 2 


- 4 9 2 


- 4 8-8 


- 


4 7 6 


- 4 6 6 


— 


4 6 2 


- 4 6 2 


- 4 6 5 





17 



Table 19. Computed values of east component (Y) of magnetic field intensity for 1945 at height 5000 km 

expressed in units of 10-4 CGS 



Geographic 
east 








G 


eograph 


ic colatitude in degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


5 


4 5 


4 2 


_ 


4 2 


4 5 


4 9 


5 6 


6 5 


7 4 


60 


2 3 


16 


13 


- 


1 3 


16 


2 2 


3 


4 1 


5 3 


9 


1 


1 





_ 


j> 


6 


10 


15 


2 3 


3 1 


12 


2 4 


1 5 


8 




4 


3 


4 


7 


9 


10 


15 


4 7 


3 8 


3 2 




3 


3 1 


3 5 


4 2 


4 8 


5 4 


180 


6 6 


6 6 


6 8 




7 1 


7 5 


7 9 


8 4 


9 


9 6 


210 


6 9 


7 9 


8 9 




9 6 


10 1 


10 4 


1 6 


1 R 


112 


2 4 


4 6 


5 8 


7 




7 9 


R 6 


9 1 


9 5 


9 8 


10 2 


2 70 


2 


6 


1 o 




1 6 


2 3 


3 


3 8 


4 6 


5 4 


3 


4 3 


5 1 


5 6 


- 


5 9 


6 


5 8 


5 4 


4 8 


4 


3 3 


7 


R 


9 


- 


a 8 


- 10 5 


- Ill 


- 115 


- 117 


- 116 


3 60 


7 


7 3 


7 7 


- 


R 2 


8 8 


Q 4 


- 10 1 


- 10 7 


- 113 




Geographic 
east 








G 


eograph 


ic colatitude in degrees 






longitude 
in degrees 


100 


110 


120 




130 


140 


150 


160 


170 
























3 


8 5 


9 7 


- 1 i) 9 


_ 


12 1 


- 13 3 


- 14 4 


- 15 4 


- 16 1 




60 


6 7 


8 2 


9 8 


- 


114 


- 12ft 


- 14 1 


- 15 2 


- 15 9 




q o 


4 2 


5 5 


6 8 


- 


8 2 


9 4 


- IO4 


- Ill 


- 115 




12 


8 


3 


4 


- 


1 3 


2 2 


3 


3 6 


4 




15 


5 9 


6 1 


6 2 




6 


5 7 


5 4 


5 


4 7 




1 a 


10 1 


10 7 


111 




115 


1 1 8 


12 


12 1 


12 2 




2 10 


J. 1 8 


12 4 


13 2 




14 


14 8 


15 5 


16 


16 4 




24 


1 R 


116 


12 4 




13 4 


14 3 


15 2 


15 8 


16 2 




2 70 


6 2 


7 3 


7 9 




8 9 


9 8 


10 6 


112 


116 




3 


3 1 


2 1 


10 







1 1 


2 2 


3 1 


3 7 




3 3 


- 112 


- 10 6 


9 7 


- 


ft 7 


7 6 


6 6 


5 7 


5 




3 60 


- 118 


- 12 1 


- 12 2 


- 


12 2 


- 12 2 


- 12 2 


- 12 2 


- 12 2 





Table 20. Computed values of vertical component (Z) of magnetic field intensity for 1945 at height 100 km 

expressed in units of 10-4 CGS ^-~-~_ ___ 



\1 


Geographic 

east 

longitude 

in degrees 








Geograph 


c colatitude 


in degrees 








10 


20 


30 


40 


50 


60 


70 


80 


90 




3 


5 17 


4 85 6 


4 5 4 6 


4 16 6 


3 56 4 


2 62 2 


136 


40 


-130 3 


60 


5 33 7 


5 18 8 


4 97 7 


4 6 11 


3 98 6 


30 18 


172 1 


24 3 


- 1 1 4 1 




90 


5 50 5 


5 5 8 1 


5 52 


5 16 9 


4 4 3 


3 27 8 


17 9 


13 3 


- 1 4 4 7 


s 


12 


5 60 6 


5 714 


559 3 


5 116 


4 26 


30 9 9 


17 4 5 


29 7 


- 1 1 5 4 




15 


5 60 6 


5 52 6 


5 110 


4389 


34 9 1 


2 53 1 


152 9 


4 2 9 


- 80 6 




18 


5 56 9 


5 34 6 


4 77 2 


4 0O2 


3 22 1 


2 49 6 


1740 


8 11 


- 34 6 




2 10 


5 55 9 


5 4 3 1 


5 5 3 


4 4 9 1 


3 82 1 


30 7 


2 217 


123 3 


12 3 




2 4 


5 5 5 4 


563 3 


5 59 6 


5 32 4 


4 73 1 


3 82 1 


2 70 6 


153 4 


4 2 




2 70 


5 4 8 5 


5 62 2 


5 7 3 4 


5 6 5 1 


5 23 6 


4 4 5 8 


3 39 8 


2207 


1 1 




3 


5 34 1 


5 316 


5 2 8 2 


5 12 4 


4 76 2 


4 17 1 


3 37 7 


2 4 3 4 


14 9 




3 3 


5 19 


4 95 2 


4 714 


4 38 


3 85 3 


3 111 


2 210 


124 8 


314 




3 60 


5 118 


4 77 1 


4 4 5 3 


4 5 9 


3 4 3 


2 4 8 8 


1313 


9 6 


- 96 4 




. 






















Geographic 

east 

longitude 

in degrees 








Geograph 


c colatitude 


in degrees 










100 


110 


' 120 


130 


^ 140 


150 I 


160 


170 






3 


- 2 23 6 


-2739 


- 292 4 


- 30 6 


- 3 19 9 


- 362 R 


- 4 27 7 


- 50 1 1 






6 


-2 24 


-290 3 


- 3 24 3 


- 34 8 1 


- 3 81 6 


-4 311 


-4880 


- 5 36 5 






90 


- 2 RO 2 


-376 2, 


-4 37 4 


-4 76 7 


- 50 8 4 


- 5 3 9 5 


- 5 6 5 8 


- 5 76 8 






12 


- 2 5R 1 


-3 83 71 


-4 84 4 


-5 56 


-600 9 


- 6 24 2 


- 6 28 2 


- 60 9 6 






150 


-2 15 9 


-3464 


-4581 


-54 3 8 


- 60 3 8 


-6 400 


- 649 3 


- 6 24 8 






180 


- 1 6 3 5 


-2882 


- 395 5 


-4 83 3 


- 5 54 8 


- 60 R 5 


-6 34 4 


- 6 20 3 






2 10 


-10 2 1 


- 2 1 5 2 


- 3 2 5 


-4 15 5 


-4 97 7 


- 5 6 1 3 


- 5 9 7 7 


-5 98 9 






2 4 


- 60 9 


-1584 


-2 53 6 


- 3 4 4 8 


-4 26 7 


-4 93 3 


- 5 4 4 


- 5 6 4 8 






2 7 


3 7 


- 97 


- 1 79 


-2 54 


- 3 26 6 


-3 9R 4 


-4 67 


- 5 2 5 2 






3 


4 5 3 


- 39 9 


- 1 10 4 ( 


r - 1 9 2 6 > 
4-3 72 5- 


r-2377 


-3 15 


-4036 


-4 917 






3 3 


- 47 8 


-110 8 


- 1 5 6 4 J 


'-2 33 9 


- 2 94 4 


- 3 78 4 


- 4 7 5 1 






3 6 


- 1 74 6 


- 2 22 9 


- 2 4 7 4 


.-2612 


-2 80 8 


- 3 21 9 


-3 90 9 


-4 79 1 





Jf/O^f 



18 



Table 21. Computed values of vertical component (Z) of magnetic field intensity for 1945 at height 300 km 

expressed in units of 10"' CGS 



Geographic 
east 








Geographic colatitude 


in degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


4771 


4485 


4184 


3805 


3230 


2366 


123 5 


9 


-1142 


60 


489 9 


4762 


4 549 


4189 


3597 


2708 


.1538 


220 


-1031 


90 


5044 


5083 


4995 


4653 


3971 


2931 


1602 


127 


-1300 


120 


5126 


5188 


5049 


4603 


3828 


2785 


1565 


258 


-1069 


150 


5126 


5033 


4651 


4004 


3195 


2316 


1389 


373 


- 76 2 


180 


509 8 


4891 


4 382 


369 5 


2981 


2297 


1578 


714 


- 336 


210 


509 5 


497 2 


4628 


4118 


3502 


2806 


2015 


1112 


111 


240 


509 6 


5149 


5092 


4 82 9 


4 287 


3473 


2476 


142 2 


406 


270 


5042 


5146 


521 7 


5115 


4 72 8 


4028 


3083 


201 9 


961 


300 


492 2 


4890 


483 9 


467 4 


4 328 


3781 


3056 


2201 


128 9 


3 30 


4 79 4 


4 57 7 


4 344 


4019 


3527 


2848 


2031 


1160 


320 


360 


4730 


4416 


4 106 


3718 


3127 


227 3 


1223 


137 


- 818 




Geographic 
east 








Geographic colatitude 


in degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


-1981 


-2464 


-267 5 


-2791 


-2993 


-3384 


-3953 


-4588 




60 


-201 3 


-2641 


-2991 


-3244 


-356 2 


-3998 


-4487 


-4899 




90 


-2503 


-3386 


-3968 


-4353 


-4658 


-4938 


-5163 


-5250 




120 


-2341 


-3472 


-4383 


-5038 


-545 2 


-5667 


-5702 


-5534 




150 


-1973 


-3146 


-4155 


-493 5 


-5482 


-5807 


-5885 


-5664 




1 80 


-1494 


-2617 


-3595 


-4400 


-5050 


-5527 


-5749 


-5620 




210 


- 937 


-1964 


-292 2 


-3784 


-4524 


-5091 


-5413 


-542 8 




240 


- 540 


-1439 


-2308 


-3135 


-3874 


-447 5 


-4901 


-5127 




270 


10 


- 868 


-1627 


-2324 


-299 3 


-3647 


-4 26 4 


-478 2 




30 


407 


-. 37 3 


-1032 


-1621 


-2231 


-293 4 


-3720 


-449 4 




330 


- 414 


-1000 


-1439 


-1799 


-2202 


-2760 


-3507 


-4353 




3 60 


-1536 


-1996 


-225 1 


-241 1 


-2619 


-3006 


-362 2 


-4392 




Table 25 


!. Compute 


i values of 


vertical co 


mponent (Z 


) of magnet 


ic field intensity for 1945 at height 500 km 








expressed in units of 10" 4 CGS 








Geographic 
east 








Geographic colatitude 


in degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


4408 


4147 


385 5 


3484 


2938 


2145 


1126 


16 


- 999 


60 


4513 


4378 


4167 


3816 


3257 


2439 


1382 


200 


- 922 


90 


4632 


4643 


4536 


4204 


3574 


2632 


1439 


120 


-115 8 


120 


469 9 


4726 


4575 


4158 


3454 


2512 


1409 


224 


- 978 


150 


469 9 


4599 


4246 


3662 


2929 


2123 


1265 


326 


- 710 


1 80 


4680 


4487 


4031 


3415 


2761 


2116 


1437 


632 


- 324 


210 


4682 


4563 


4249 


3783 


3216 


2571 


1839 


1008 


92 


240 


4686 


4719 


4649 


4395 


3899 


3167 


227 2 


1319 


391 


270 


4644 


4721 


4 762 


4648 


4286 


3653 


2807 


1852 


896 


300 


4543 


4506 


4443 


4275 


3946 


3440 


277 5 


1997 


1170 


330 


4433 


4235 


4010 


3698 


3237 


2614 


1871 


107 9 


314 


3 60 


4377 


4092 


3792 


341 5 


2861 


2084 


1142 


167 


- 696 




Geographic 
east 








Geographic 


; colatitude 


in degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


-1764 


-2225 


-245 3 


-2594 


.2800 


-3158 


-3660 


-4212 




60 


-1816 


-2409 


-276 3 


-3022 


-3323 


-3712 


-4134 


-4486 




90 


-2246 


-3060 


-3611 


-5985 


-4276 


-4530 


-4725 


-4794 




120 


-2129 


-3153 


-3980 


-4560 


-4962 


-5162 


-5194 


-5041 




150 


-1808 


-286 6 


-3780 


-4491 


-4992 


-5285 


-5352 


-5152 




180 


-1370 


-2385 


-3278 


-4017 


-4609 


-5035 


-5227 


-5110 




210 


- 861 


-1796 


-2670 


-3455 


-4124 


-4633 


-4920 


-4937 




240 


- 480 


-1309 


-2106 


-2859 


-3529 


-4074 


-446 2 


-4670 




270 


10 


- 780 


-1485 


-2133 


-2750 


-3347 


-3904 


-4369 




300 


367 


- 350 


- 966 


-1522 


-2092 


-2733 


-3436 


-4119 




330 


- 360 


- 906 


-1328 


-1682 


-2071 


-2587 


-3855 


-4000 




360 


-1357 


-1T94 


-2055 


-2231 


-2446 


-2809 


-3361 


-4037 





Table 23. 



Computed values of vertical component (Z) of magnetic field intensity for 1945 at height 1000 km 
expressed in units of 10-4 CGS 



Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 



30 


363 9 


3427 


3166 


2826 


235 2 


1706 


910 


57 • 


- 729 


60 


3703 


3577 • 


337 5 


3057 


2577 


1909 


1076 


161 « 


- 711 


90 


3778 


3744 


3613 


3310 


278 9 


2043 


1118 


102 • 


- 887 


120 


3820 


3793 


3631 


3275 


271 1 


1967 


1098 


160 


- 790 


150 


382 2 


3713 


3422 


2960 


2377 


1721 


101 1 


239 < 


- 597 


1 80 


3815 


365 3 


3300 


2819 


228 8 


1740 


1152 


4 80 


- 289 


210 


3824 


3718 


3464 


3088 


262 4 


2088 


1480 


801 


62 


240 


3834 


3834 


3747 


3520 


3118 


2544 


1847 


1096 


349 


270 


3810 


3845 


3837 


3710 


340 3 


290 2 


2246 


1505 


751 


30 


3744 


3701 


362 2 


3457 


3170 


2749 


2211 


1589 


930 


330 


3666 


3507 


3306 


302 8 


263 9 


2133 


153 8 


906 


29 1 


3 60 


3623 


3397 


3130 


2790 


2 321 


1700 


966 


209 ■ 


-47 2 



Geographic 
east 

in flppTPPi 



h« t ) Vfl " 






in degrees 



Geographic colatitude in degrees 



100 



110 



120 



130 



140 



150 



s « 
-or. 



YVtO-C-'' 



30 
60 
90 
120 
150 
1 80 
210 
240 
270 
300 
330 
360 



•1345 

•1427 

■1745 

■1699 

•1466 

1114 

703 

36 4 

3 9 

287 

25 9 

1014 



175 3 

1938 

241 2 

2508 

229 7 

1916 

145 3 

1045 

609 

301 

720 

1399 



1996 

•2278 

■2890 

•3168 

•3021 

263 2 

2154 

169 3 

1196 

82 2 

1096 

165 5 



2170 

2536 

3228 

3654 

3591 

3230 

•2781 

•2297 

■1737 

■1300 

•142 6 

■1850 



237 3 
279 8 
3484 
3971 
3995 
3705 
3309 
2830 
2247 
1781 
1774 
2067 



-266 5 
-3097 
-3689 
-4139 
-422 7 
-4034 
-3705 
-326 4 
-272 9 
-2296 
-2200 
-2377 




3440 

3644 
•3869 
•4047 
•412 3 
•4085 
•3950 
•3748 
•3528 
•3351 
•3271 
•3305 



/GO 



-30W 
- Hl<°6> 

-3IC8 
-2838 



Table 24. Computed values of vertical component (Z) of magnetic field intensity for 1945 at height 5000 km 

expressed in units of 10~4 CGS 



Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 



30 


1045 


984 


893 


774 


636 


454 


364 


69 


- 118 


60 


1045 


988 


903 


785 


635 


456 


355 


44 


- 161 


90 


1048 


996 


916 


801 


648 


463 


349 


33 


- 202 


120 


1051 


1001 


918 


799 


644 


456 


344 


18 


- 211 


150 


1056 


1002 


913 


788 


633 


453 


354 


41 


- 177 


1 80 


1063 


1013 


93 4 


803 


657 


489 


305 


108 


98 


310 


1072 


1035 


963 


860 


738 


573 


398 


208 


10 


340 


1080 


1060 


1010 


93 9 


816 


673 


503 


317 


123 


370 


1083 


1069 


1033 


96 6 


868 


739 


582 


406 


220 


300 


1075 


1054 


1009 


938 


840 


716 


570 


407 


235 


330 


1063 


1033 


95 6 


864 


746 


607 


451 


287 


120 


360 


1051 


99 5 


910 


798 


659 


499 


323 


143 


29 



Geographic 

east 

longitude 

in degrees 



Geographic colatitude in degrees 



100 



110 



120 



130 



140 



150 



160 



170 



30 
60 
90 

130 
150 
180 
210 
340 
370 
300 
330 
360 



388 


m 


433 


349 


- 


513 


413 


- 


596 


430 


- 


689 


393 


— 


594 


305 


— 


504 


190 


- 


385 


71 


• 


261 


33 


m 


151 


61 


- 


108 


39 


— 


190 


188 


- 


337 



555 
650 


- 


660 


- 754 


- 


76 3 


- 856 


74f 


— 


871 


- 962 


79 9 


- 


933 


-1038 


773 


— 


918 


-1034 


685 


» 


839 


- 960 


566 


- 


737 


- 860 


440 


— 


603 


- 744 


33 5 


- 


487 


- 636 


373 


- 


437 


- 574 


330 


- 


46 3 


- 589 


449 


- 


5S9 


- 662 



840 

932 

1034 

1084 

1089 

•1041 

• 959 
> 861 

• 769 

• 712 

• 713 

• 764 



- 919 

- 989 
-1057 
-1102 
-1110 
-1079 
-1021 

- 949 

- 881 

- 838 

- 832 

- 863 



- 985 
■1033 
•1059 
•1083 

• 1088 

• 1074 

• 1043 

• 1005 

- 969 

- 946 

• 941 

- 955 



20 



Table 25. Computed values of magnetic potential (V), main field, for 1945 
expressed in units of 10^ CGS 



Geographic 
east 


Geographic colatitude in degrees 


longitude 


10 


20 




30 


40 


50 


60 


70 


80 


90 


in degrees 






















3 


- 1 8 4 4 


-1736 


- 1 


59O -1400 


-115 2 - 83 9 - 473 - 87 


27 7 


6 


-1R57 


- 1 7 7 1 


- 1 


6 4 1 -14 5 5 


-1. 202 - 8 79 - 496 - 83 


317 


o n 


-18 7 7 


-18 18 


- 1 


707 -1535 


-12 5 7 - 90 5 - 487 - 37 


4 4 


13 


-18 9 1 


- 1 8 3 4 


- 1 


7 15 -1516 


-1235 - 884 - 482 - 52 


38 4 


15 


-1R97 


- 1 8 1 8 


- 1. 


6 6 3 - 1. 4 3 4 


-1148 - 823 - 470 - 91 


30 7 


IPO 


- 1 9 3 


-18 15 


- 1 


647 -1419 


-1156 - 871 - 562 - 219 


15 6 


310 


-1914 


- 1 8 5 4 


- 1 


7 2 6 - 1 5 3 9 


-130 5 -1032 - 72 5 - 386 


2 6 


2 4 


- 1 9 2 5 


- 1 9 6 


- 1 


839 -1709 


-1507 -12 3 5 - 912 - 559 


- 20 1 


2 70 


-1928 


-19 18 


- 1 


881 -17 8 8 


-1622 -1379 -1075 - 733 


- 3 8 


3 


- 1 9 


-187 1 


- 1 


8 1 -17 5 


-1544 -1328 -1063 - 761 


- 4 4 1 


3 3 


- 1 8 7 


-1 7o 6 


- 1 


6 8 9 - 1 5 3 8 


-1336 -10 8 5 - 19 1'- 491 


- 18 7 


3 60 


-184 8 


-174 3 


- 1 


6O4 -1422 


-118 5 - R 8 9 - 5 5 1 - 201 


12 5 




Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


100 


110 




120 


130 


140 


150 


160 


170 




3 


5 8 4 


8 2 




9 9 7 114 1 


1282 1^36 1600 175 5 




60 


66 4 


9 4 


1 


15 1 13 2 1 


1 4 7 3 16 18 17 4 6 18 3 6 




9 


80 1 


112 9 


1385 1580 


1728 1.83 8 1906 19 2 




12 


8 2 


117 8 


1 


4 9 3 17 3 4 


1900 1996 2024 1982 




1 5 


711 


1 9 4 


1 


4 3 17 1 


1.8 97 2017 2054 2004 




18 


54 5 


9 2 2 


1 


2 5 9 15 4 4 


1. 769 1926 2000 198 1 




210 


34 1 


69 9 


3 


3 4 13 3 3 


15 8 4 17 7 5 1 P. 9 19 2 1 




2 4 


15 


4 8 9 




8 12 110 9 


13 7 15 8 5 1. 7 4 4 18 4 




2 70 


3 5 


29 




5 9 3 8 7 5 


1 137 1377 1.588 1757 




3 


- 12 1 


18 1 




4 6 1 72 2 


9 7 5 12 2 7 1 4 7 3 16 9 5 




3 3 


9 7 


35 2 




5 7 8 7 8 5 


990 1208 14 42 1.673 




3 60 


4 8 


63 7 




8 19 9 7 5 


1128 1298 1493 169 5 





Table 26. Computed values of magnetic potential (V), residual field, for 1945 
expressed in units of 105 CGS 



Geographic 
east 








Geographi 


c colatitude 


in 


degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


6 1 


7 


6 1 




4 7 




4 7 




7 4 


12 8 


183 


20 8 


6 


1 6 


2 8 


8 1 


- 


12 6 


- 


14 5 


- 


12 4 


6 8 


5 


6 3 


00 


2 4 


- 114 


- 20 6 


_ 


27 1 


- 


2 8 8 


- 


25 2 


- 16 9 


6 3 


3 4 


12 


4 1 


- 13 7 


- 22 2 


- 


27 4 


- 


2 8 


- 


24 6 


- 18 


9 5 


3 


15 


3 1 


9 2 


- 12 7 


- 


13 5 


- 


12 7 


- 


1 1 


8 7 


5 


6 


180 


8 


3 1 


2 8 


- 


1 4 


- 


7 


- 


1 4 


2 2 


13 


2 1 


2 10 


1 4 


1 


5 


_ 


3 


- 










5 


1 9 


4 2 


2 4 


3 6 


9 


2 6 


- 


5 4 


- 


6 1 


- 


4 2 


7 


2 7 


5 2 


2 7 


5 9 


3 7 


10 


_ 


5 8 


- 


8 6 


- 


8 5 


6 1 


3 


10 


3 


8 4 


9 1 


6 9 




3 6 




4 


- 


1 9 


3 3 


4 1 


5 3 


3 3 


9 9 


13 6 


14 8 




14 7 




14 6 




14 9 


15 2 


14 3 


1 1 ^ 


3 6 


9 3 


13 2 


14 9 




1 5 5 




16 9 




20 1 


24 1 


26 8 


26 




Geographic 
east 








Geographi 


z colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


17 8 


90 


3 5 


_ 


16 2 


_ 


25 4 


_ 


28 5 


- 25 3 


- 17 4 




60 


7 7 


3 6 


4 2 


- 


12 5 


- 


18 1 


- 


19 4 


- 17 


- 12 5 




90 


9 8 


115 


9 1 




4 4 


- 


1 


- 


3 2 


49 


6 1 




12 


8 2 


14 8 


18 4 




18 5 




15 9 




115 


6 1 


2 




15 


7 6 


14 5 


19 6 




218 




212 




17 9 


12 


3 4 




18 


7 5 


12 9 


16 9 




18 9 




19 1 




17 2 


12 4 


4 




2 10 


7 


9 8 


12 




13 4 




13 7 




12 3 


8 4 


1 5 




24 


6 3 


6 1 


5 7 




5 1 




4 1 




2 5 





3 3 




2 70 


9 


2 8 


5 9 


- 


9 2 


- 


116 


- 


12 3 


- 114 


9 5 




3 


7 8 


- 12 


- 17 6 


- 


2 3 2 


- 


26 7 


- 


26 5 


- 22 3 


- 15 4 




33 


5 6 


3 


- 13 4 


- 


23 6 


- 


3 8 


- 


32 7 


- 2 8 4 


- 19 1 




3 6 


20 2 


9 7 


3 7 


- 


17 3 


- 


27 7 


- 


32 


- 29 


- 19 8 





21 



Table 27. Computed values of the vertical gradient of north component of magnetic field intensity 
( 3X/ 3r), main field, for 1945 expressed in units of 10-12 CGS 



Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


- 4 2 


_ 


4 6 6 


_ 


52 S 


- 7 3 


- 1 1 1 


- 1 5 5 2 


— 


18 5 6 


- 1 8 6 


- 1 5 4 2 


6') 


- 2 o 5 


- 


29 5 


- 


4 6 2 


- 73 9 


- 1 1 3 3 


- 1 5 7 7 


- 


192 4 


- 2 fi 


- 1 7 5 5 


9 


4 2 


- 


6 4 


- 


36 1 


- 8 15 


- 1 3 4 2 


-183 2 


- 


2 16 


- 2 2 3 1 


- 2 1 R 


12 


12 6 


- 


7 9 


- 


47 8 


- 96 9 


-14 18 


- 1 7 4 1 


- 


19 3 


- 20 1 1 


-19 9 5 


15 


1 8 


- 


386 


- 


83 2 


- 1 1 6 6 


-133 2 


-14.0 1 


_ 


14 9 


- 1 64 9 


-1806 


180 


8 5 


- 


57 7 


- 


96 


- 1 1 R 


- 1 R 


- 1 6 7 


- 


1. 21 4 


- 1 4 9 5 


-174 1 


210 


2 6 


- 


37 9 


- 


6 8 6 


- 8 9 4 


- 1 3 


- 1 16 


- 


1319 


- 1 4 8 1 


- 1 5 8 7 


24 


10 9 


- 


6 


- 


25 


- 62 4 


- 1. 5 3 


-14 0R 


_ 


1 59 2 


- 1 6 1 


- 1 5 1 6 


2 7 


113 




13 4 


- 


3 1 


- 39 4 


- 8 6^ 


- 1 2 9 5 


- 


156 7 


- 1 6 4 1 


-15 6 1 


3 


7 6 


- 


6 


- 


17 3 


- 4 0R 


- 703 


- 9 9 2 


- 


12 3 


-138 3 


- 1 4 1 8 


3 3 


- 32 4 


- 


33 4 


- 


4 2 2 


- 6 3 7 


- 9 2 5 


- 1 . 1 8 2 


_ 


132 7 


- 1 3 3 9 


- 1 23 6 


3 60 


- 4 6 5 


— 


4 7 4 


- 


516 


- 73 3 


- 1 10 7 


- 1 4 7 7 


- 


16 6 6 


-159 9 


- 1. 3 2 4 




Geographic 
east 












Geograph 


ic colatitude in degrees 








longitude 
in degrees 


100 


110 


120 


130 


140* 


150 


160 


170 




3 


- 1 3 6 


_ 


55 5 


_ 


2 7 9 


- 27 7 


- 4 8 5 


- 75 8 


_ 


93 


- 89 1 




60 


-13 6 8 


- 


77 


- 


47 5 


- 4 5 5 


- 6O4 


- 73 4 


- 


6 9 8 


- 47 8 




90 


-159 6 


- 


1119 


■ - 


74 3 


- 5 4 3 


- 47 6 


- 4 19 


- 


2 6 4 


1 7 




12 


- 1 8 5 8 


- 


15 8 4 


- 


12 12 


- 82 5 


- 4 9 2 


- 215 




6 8 


4 8 




15 


- 1 P 3 6 


- 


16 7 5 


- 


136 6 


- 1. 1 3 


- 6 R 


- 34 2 




6 5 


54 3 




18 


- 1 7 9 1 


- 


162 6 


- 


135 7 


-110 4 


- 87 4 


- 57 2 


- 


116 


4 4 2 




2 1 


- 1 5 9 8 


- 


15 2 2 


- 


13 9 5 


- 1 23 7 


- 10 2 4 


- 714 


- 


2 9 4 


18 6 




24 


- 1 4 3 


- 


1 37 8 


- 


1 32 9 


- 1. 2 2 7 


- 10 4 9 


- 80 7 


- 


52 3 


- 20 2 




2 70 


-1406 


- 


125 


- 


1 1 3 5 


-10 6 9 


-10 3 7 


- 99 6 


- 


89 1 


- 67 8 




3 


-132 4 


- 


114 5 


- 


97 9 


- 92 7 


- 1 1 3 


- 1 1 5 4 


- 


12 9 


- 10 8 




3 3 


- 10 4 9 


- 


82 7 


_ 


64 9 


- 60 9 


- 75 1 


- 1 1 2 


- 


123 2 


-124 2 




3 60 


- 9 5 5 


- 


60 8 


- 


37 3 


- 32 1 


- 47 6 


- 77 8 


- 


10 6 8 


- 1 1 5 5 




Tab 


le 28. Coi 


nputed valu 


es 


af the ve 


■rtical gradient of east 


component 


of 


magnetic field intensity 






( 3Y/ a 


r), 


main field, for 1945 expressed in units of 10 


-12 CGS 






Geographic 
east 












Geograph 


ic colatitude in degrees 








longitude 


10 




20 




30 


40 


50 


60 




70 


80 


90 


in degrees 


























3 


- 23 2 


_ 


23 4 


_ 


19 1 


- 15 1 


- 13 5 


- 13 2 


_ 


117 


7 3 


1 


60 


- 4 7 


- 


46 5 


- 


4 3 9 


- 35 9 


- 26 1 


- 17 1 


- 


9 3 


2 1 


5 8 


90 


- 34 4 


- 


35 3 


- 


311 


- 22 3 


- 119 


3 2 




1 8 


4 3 


8 2 


120 


- 110 




5 9 




210 


30 


29 9 


20 4 




5 


- 10 9 


- 215 


150 


5 5 




27 1 




4 16 


4 4 


35 


19 5 




4 1 


6 6 


- 12 2 


18 


3 2 




3 6 


- 


3 


7 4 


- 15 1 


- 211 


- 


24 7 


- 27 


- 29 4 


2 10 


3 7 


- 


26 1 


- 


4 4 8 


- 52 7 


- 47 9 


- 34 7 


- 


211 


- 141 


t 16 


24 


4 2 


- 


18 6 


- 


37 


- 4 6 9 


- 4 7 4 


- 4 11 


- 


32 1 


- 24 5 


- 20 9 


2 70 


25 




20 1 




14 7 


7 4 


2 5 


- 13 8 


- 


23 8 


- 29 8 


- 319 


3 


38 5 




46 4 




50 4 


50 6 


4 7 


4 3 




31 4 


22 3 


14 


3 3 


30 8 




37 7 




39 2 


40 1 


4 4 4 


52 1 




60 6 


66 1 


66 5 


3 60 


5 8 




9 




9 3 


8 1 


8 2 


12 




19 8 


29 8 


38 4 




Geographic 
east 












Geograph 


ic colatitud< 


; in degree 


s 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


4 9 




9 




12 3 


17 9 


28 7 


4 4 6 




618 


74 5 




60 


15 4 




26 8 




39-5 


53 


66 6 


79 4 




90 1 


97 




9 


17 2 




32 5 




518 


70 4 


84 1 


911 




93 


92 8 




12 


- 23 2 


- 


16 


- 


2 4 


13 5 


28 7 


4 15 




514 


5 8 5 




15 


- 15 1 


- 


18 2 


- 


219 


- 24 2 


- 219 


- 13 7 


- 


1 7 


9 4 




18 


- 32 8 


- 


36 7 


- 


39 9 


- 4 10 


- 4 1 


- 38 3 


- 


36 7 


- 36 3 




2 10 


- 23 9 


- 


32 5 


- 


37 9 


- 4 5 


- 43 3 


- 50 1 


- 


60 9 


- 72 1 




2 4 


- 219 


- 


27 


- 


35 3 


- 4 6 1 


- 5 8 9 


- 72 4 


- 


85 


- 94 3 




2 7 


- 32 6 


_ 


35 5 


- 


4 3 6 


- 56 4 


- 70 9 


- 83 1 


- 


9 2 


- 92 7 




3 


6 9 


- 





- 


8 4 


- 19 2 


- 32 1 


- 45 


- 


55 3 


- 6 12 




3 3 


62 




54 6 




4 6 


36 3 


24 8 


114 


- 


1 9 


- 119 




3 60 


4 3 1 




4 3 




39 9 


36 3 


34 3 


3 4 4 




35 5 


36 4 





22 



Table 29. Computed values of the vertical gradient of vertical component of magnetic field intensity 
( 3Z/ 8r), main field, for 1945 expressed in units of 10-12 CGS 



Geographic 
east 








Geographic colatitude 


in degrees 






longitude 


10 


20 


30 


40 


50 


60 


70 


80 


90 


in degrees 




















3 


-2193 


- 2 3 


- 2 7 


-2036 


- 1 9 2 2 


-14 9 - 72 5 


20 4 


102 4 


6 


- 3 3 7 4 


- 2 3 7 2 


- 2 39 8 


- 2 38 8 


-2231 


-18 6 - 1 n 68 


- 13 2 


74 8 


9 


- 2 5 8 4 


- 2 R 2 4 


-30O 3 


- 2 9 R 1 


- 2 6 6 4 


-2018 -1092 


2 2 


99 1 


13 


- 2 70 9 


- 30 9 


-3141 


-2 97 1 


- 2 4 9 3 


-1R09 -1. 034 


- 23 4 


57 4 


1 5 


- 2 70 7 


- 2 8 5 


- 2 61 1 


-2 17 2 


- 1 6 5 3 


-1193 - 794 


- 33 7 


2 8 1 


iflO 


- S 6 4 5 


- 2 5 6 


- 217 3 


- 1 67 7 


- 1 2 9 7 


-1096 - 930 


- 5 8 4 


2 7 


?,10 


-2600 


- 2 5 8 4 


- 2 3 R 4 


- 2 8 9 


-3.78 5 


-34R9 -1148 


- 69 9 


- 14 1 


2 4 


- 2 5 6 1 


- 2 7 3 5 


- 2 R 7 1 


- 2 R 4 1 


- 2 54 3 


_ 3 9 r 3 -12 8 


- 59 9 


4 2 


2 7 


- 2 4 6 7 


- 2 6 7 9 


- 2 94 3 


- 3 7 5 


- 2 92 9 


-2473 -1.79 4 


- 1 4 6 


- 36 4 


3 


- 2 3 1 6 


- 2 3 6 7 


- 2 4 R 7 


- 2 5 4 R 


- 24 7 


-2230 -1.844 


- 1. 3 4 4 


- 7 R 7 


3 3 


- 2 1. 7 6 


- 2 5 7 


- 2 4 9 


- 2 1 7 


- 1 R 4 


-14 8 2 -1.00 1 


- 4 8 1 





3 6 


-21 2 3 


- 1 9 3 3 


-19 18 


- 1 92 4 


- 1 7 3 1 


-1227 - 491 


27 7 


R R 7 




Geographic 
east 








Geographic colatitude 


in degrees 






longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 n 


15 8 


15 9 5 


14 4 


116 3 


3.0 9 4 


1312 17 9 2 


2 39 4 




6 o 


13 2 2 


14 9 1 


1 3 R 2 


1.258 


134 7 


17 1 2 19 8 


2 65 1 




q o 


175 6 


2 1. R 


2 316 


2 3 3 


2 39 2 


2573 2808 


296 2 




12 


1 3 6 ,9 


2 R 3 


2 63 5 


2 9 R R 


3 1 R 


3 2 8 1 3 3 15 


3 22 5 




15 


10 4 4 


1R10 


2 4 3 4 


2 R 6 6 


3 16 2 


3379 34R3 


3 35 8 




1 BO 


7 9 5 


15 11 


2 5 


2 4 4 6 


2 8 R 


3 16 8 3 4 8 


3 35 2 




2 1 


4 6 9 


10 6 1 


16 


2 10 


2 57 1 


2979 3231 


3 22 6 




340 


4 4 


8 2 5 


12 8 5 


1 7 R 


2 24 8 


262 5 2879 


2 99 




P70 


18 3 


59 9 


9 2 3 


12 16 


153 


1P9R 2 3 06 


2 6 R 2 




3 


- 26 1 


14 


3 8 4 


5 4 1 


75 9 


116 2 17 5 2 


2 39 9 




3 3 


3 8 7 


62 6 


70 2 


6 R 


713 


97 1516 


2 24 3 




3 6 


12 4 4 


135 1 


127 3 


1112 


10 16 


114 3 15 7 9 


2 24 8 





Table 30. Computed values of the vertical gradient of north component of magnetic field intensity 
( 3X/ 3r), residual field, for 1945 expressed in units of 10-12 CGS 



Geographic 
east 








Geographic colatitude in 


degrees 








longitude 
in degrees 


10 


20 


30 




40 


50 




60 


70 




80 


90 


























3 


- 12 


7 4 


2 3 8 




23 4 


2 4 


_ 


2 R 


- 4 R 5 


_ 


43 3 


- 10 2 


60 


22 8 


37 3 


419 




32 9 


9 


- 


23 7 


- 50 7 


- 


55 5 


- 315 


9 


561 


6 R 5 


59 5 




32 


6 4 


- 


4 4 8 


- 714 


- 


76 5 


- 57 8 


12 


65 9 


6 8 2 


4 9 




17 5 


- 13 1 


- 


35 1 


- 47 8 


- 


54 4 


- 55 5 


1 5 


4 8 R 


315 


R 1 


- 


7 


R 6 


- 


4 3 


6 1 


- 


19 2 


- 366 


1. R 


26 2 


8 


- 15 4 


- 


10 6 


8 6 




22 8 


17 2 


- 


60 


- 301 


2 10 


17 3 


6 5 


10 


- 


7 


3 9 




60 


1 6 


- 


7 2 


- 147 


24 


17 4 


30 9 


30 7 




15 7 


7 1 


- 


25 4 


- 30 3 


- 


21 6 


7 7 


2 7 


9 3 


37 


45 1 




32 1 


6 2 


- 


18 5 


- 30 7 


- 


27 1 


- 12 1 


3 


- 1 R 


16 2 


29 8 




29 7 


215 




111 


2 4 


j 


1 5 


2 1 


3 3 


- 29 4 


5 1 


10 5 




117 


3 4 


- 


4 6 


5 




3 9 


20 3 


3 60 


- 313 


7 5 


117 




115 


6 8 


- 


27 9 


- 4 4 6 


- 


19 8 


115 




Geographic 
east 








Geographi 


c colatitud( 


; in 


degree 


s 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


4 8 6 


7 8 


94 2 




79 3 


40 


_ 


R 2 


- 4 8 5 


- 


691 




60 


23 


51 8 


67 7 




52 7 


17 7 


- 


17 6 


- 38 2 


- 


4 12 




90 


- 112 


14 


36 6 




38 3 


23 9 




6 3 


2 9 


- 


1 




12 


- 37 6 


- 32 9 


- 10 8 




9 3 


21 3 




25 6 


29 1 




37 6 




15 


- 34 4 


- 39 8 


- 2 3 


- 


5 3 


7 4 




18 5 


34 8 




57 3 




18 


- 27 7 


- 30 7 


- 16 


- 


6 5 


2 4 




6 1 


2 8 2 




59 4 




2 10 


5 8 


- 15 2 


- 12 3 


- 


10 1 


5 9 




4 9 


24 5 




48 6 




2 4 


13 3 


3 8 


1 1 


- 


4 


2 




7 4 


14 5 




23 2 




2 70 


17 2 


19 6 


24 8 




20 9 


9 8 


- 


3 9 


- 14 1 


- 


15 9 




3 


25 6 


30 5 


4 10 




35 9 


13 1 


- 


18 6 


- 4 4 7 


- 


54 8 




3 3 


52 


60 1 


70 8 




63 6 


34 4 


- 


9 9 


- 53 


- 


77 3 




3 6 C 


59 3 


77 8 


92 2 




8 4 5 


52 5 




2 7 


- 4 8 3 


— 


80 7 





23 



Table 31. Computed values of the vertical gradient of east component of magnetic field intensity 
( 8Y/ 3r), residual field, for 1945 expressed in units of 10-12 CGS 



Geographic 
east 








Geographic colatitude in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


- 5 19 


- 53 1 


- 2 4 1 


_ 


4 3 8 


_ 


4 2 2 


_ 


4 19 


4O4 


- 3 6 


- 29 7 


60 


- 6 3 


- 6 8 8 


- 52 5 


- 


5 8 3 


- 


4 8 4 


- 


39 4 


- 316 


- 2 4 4 


- 16 4 


P 


- 4 4 3 


- 4 5 2 


- 4 11 


- 


32 3 


- 


2 18 


- 


13 1 


8 1 


5 5 


16 


12 


5 9 


110 


12 4 




3 5 1 




3 5 




2 5 5 


100 


5 8 


- 16 4 


1 5 


?! 4 3 


4 5 9 


3 6 6 




62 8 




53 8 




38 3 


22 9 


12 1 


6 5 


18 


3 5 


310 


3 




19 9 




12 2 




6 2 


2 6 


3 


2 


2 1 


?49 


?! 4 


- 39 8 


- 


24 


- 


19 2 


- 


6 1 


7 4 


14 4 


12 6 


34 


2 6 5 


3 6 


- 2 8 4 


- 


24 6 


- 


25 1 


- 


18 8 


9 8 


2 2 


1 3 


2 7 


34 9 


30 


24 7 




17 3 




7 4 


- 


3 9 


- 13 8 


- 19 9 


- 22 


3 o n 


33 4 


4 13 


5 9 




4 5 5 




4 2 




35 2 


26 3 


17 2 


8 O 


3 3 


1?! 1 


19 


4/5 1 




2 14 




25 6 




33 4 


4 19 


4 7 4 


4 7 7 


3 60 


- 3 15 


- 18 3 


9 3 


- 


19 1 


- 


19 1 


- 


15 3 


7 4 


2 4 


110 




Geographic 
east 








Geographic colatitude 


■ in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


146 


150 


160 


170 




3 


- ? 3 7 


- 19 6 


- 16 3 


_ 


10 7 









1 6 O 


33 2 


4 5 8 




60 


6 8 


4 5 


17 2 




30 8 




4 4 3 




5 7 1 


6 7 8 


74 7 




9 


7 3 


22 5 


4 1 8 




60 5 




74 2 




812 


83 1 


82 9 




IPO 


- 1 « 1 


- 10 9 


2 6 




18 6 




33 8 




4 6 5 


56 5 


6 3 6 




1 5 


3 5 


5 


3 2 


- 


5 5 


- 


3 2 




4 9 


17 


28 1 




180 


5 4 


9 4 


- 12 5 


- 


13 6 


- 


12 8 


- 


10 9 


9 4 


- 8 9 




3 10 


4 7 


3 8 


9 3 


- 


118 


- 


14 7 


- 


214 


- 32 2 


- 4 3 4 




?! 4 


3 


4 7 


- 13 


- 


2 3 8 


- 


3 6 6 


- 


5 2 


- 62 7 


- 72 




?! 7 


- 2 2 6 


- 2 5 6 


- 33 6 


- 


4 6 5 


- 


6 10 


- 


73 1 


- 80 3 


- 82 7 




3 


1 8 


5 1 


- 13 5 


- 


24 3 


- 


37 2 


- 


50 1 


- 604 


- 66 3 




3 3 o 


4 3 3 


35 9 


27 3 




17 6 




6 1 


- 


7 2 


- 20 6 


- 30 6 




3 6 


15 7 


15 6 


12 5 




8 9 




7 




7 


8 1 


9 





Table 32. Computed values of the vertical gradient of vertical component of magnetic field intensity 
( 3Z/ 9r), residual field, for 1945 expressed in units of 10-12 CGS 



Geographic 
east 








Geograph 


ic colatitude in degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


62 4 


64 1 


4 3 6 


103 


- 14 9 


- 13 9 16 4 


6 4 


92 2 


60 


39 6 


2 5 


9 1 


- 4 2 3 


- 6^7 


_ ^00 - 435 


1 


37 3 


90 


15 6 


- 30 5 


- 7 8 2 


- 1 1 2 7 


- 1 2 3 2 


-10 5 2 - 621 


6 1 


4 4 3 


12 


2 6 


- 4 9 9 


- 9 3 4 


-113 3 


- 1 8 1 


- 8 6 5 - 5 8 8 


- 29 9 


U 


15 


5 1 


- 25 1 


- 3 4 


- 25 3 


- 14 4 


- 139 - 227 


- 27 6 


16 4 


18 


15 6 


7 7 


22 1 


4 


4 j 


17 1 • 13 1 


p 8 


- 17 


2 10 


25 3 


15 6 


16 


18 2 


14 3 


3 8 - 6 7 


9 9 


3 9 


2 4 


34 


9 9 


- 19 


- 39 4 


- 4 5 


- 2 1 7 5 7 


26 9 


33 2 


2 7 


4 6 3, 


214 


- 17 5 


- 517 


- 65 9 


- 55 9 - 295 


7 


183 


3 


619 


53 4 


29 3 


2 5 


- 17 9 


- 293 - 320 


- 27 9 


- 213 


3 3 


7 3 7 


8 1 


6 6 7 


4 7 4 


35 2 


34 3 4 O 2 


4 5 7 


4 4 6 


3 60 


74 7 


8 4 


6 7 4 


4 8 


27 1 


3 8 4 6 8 


97 3 


10 8 5 




Geographic 
east 








Geograph 


ic colatitud 


e in degrees 






longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


9 r 


514 


- 12 3 


- 76 5 


- 1 17 7 


-1232 - 948 


- 4 5 9 




60 


45 3 


15 4 


- 3 8 2 


- 87 9 


- 109 9 


- 979 - 63 5 


- 25 




90 


717 


6 8 


40 2 


5 9 


- 16 5 


_ 194 - 85 


3 1 




12 


30 4 


55 9 


69 8 


69 7 


60 5 


50 413 


2 8 9 




1 5 


10 5 


40 6 


60 8 


67 4 


66 9 


6 6 2 62 4 


4 4 5 




18 


9 9 


33 9 


43 8 


44 3 


4 7 4 


57 4 63 4 


4 8 1 




2 10 


70 


17 1 


24 8 


32 7 


4 3 1 


53 6 56 


4 7 




2 4 


27 3 


19 2 


17 


216 


2 8 2 


318 30 1 


219 




2 70 


22 2 


12 8 


4 2 


- 215 


- 32 3 


- 32 1 - 212 


5 8 




3 


- 19 6 


- 30 5 


- 5 5 9 


- 87 


-107 8 


-1045 - 75 7 


- 33 7 




3 3 


32 6 


6 


- 35 1 


- 82 9 


-120 6 


-1300 -1037 


- 515 




3 6-0 


93 9 


55 3 


5 


- 5 8 6 


- 1 6 2 


-12 5 1 -10 5 9 


- 5 5 2 





24 



FIGURES A -G and 1-8 



Figure Page 

A. The geomagnetic declination in degrees of arc for 1945 26 

B. The geomagnetic horizontal intensity in CGS unit for 1945 26 

C. The geomagnetic vertical intensity in CGS unit for 1945 27 

D. The geomagnetic inclination in degrees of arc for 1945 27 

E. The geomagnetic total intensity in CGS unit for 1945 28 

F. The geomagnetic north component in CGS unit for 1945 28 

G. The geomagnetic east component in CGS unit for 1945 29 

1-4. Current function in 10^ amperes for thin spherical shell at depths 0, 1000, 2000, and 

3000 km within Earth to reproduce surface main field, epoch 1945 30 

5-8. Current function in 10^ amperes for thin spherical shell at depths 0, 1000, 2000, and 

3000 km within Earth to reproduce residual (nondipole part) of main field, epoch 1945 ... 32 



25 




FIG. A -THE GEOMAGNETIC DECLINATION IN DEGREES OF ARC FOR 1945 




FIG. B -THE GEOMAGNETIC HORIZONTAL INTENSITY IN CGS-UNIT FOR 1945 



26 




FIG. C -THE GEOMAGNETIC VERTICAL INTENSITY IN CGS-UNIT FOR 1945 




FIG. D —THE GEOMAGNETIC INCLINATION IN DEGREES OF ARC FOR 1945 



27 




FIG. E -THE GEOMAGNETIC TOTAL INTENSITY IN CGS-UNIT FOR 1945 




FIG. F —THE GEOMAGNETIC NORTH COMPONENT IN CGS-UNIT FOR 1945 



28 




FIG. G -THE GEOMAGNETIC EAST COMPONENT IN CGS-UNIT FOR 1945 



29 




FIG. I— CURRENT-FUNCTION IN I0 7 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH ZERO WITHIN EARTH TO REPRODUCE 

SURFACE MAIN FIELD, EPOCH 1945 




FIG. 2-CURRENT-F UNCTION IN I0 7 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 1000 KM WITHIN EARTH TO REPRO- 
DUCE SURFACE MAIN FIELD, EPOCH 1945 



30 




FIG. 3— CURRENT-FUNCTION IN I0 7 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 2000 KM WITHIN EARTH TO REPRO- 
DUCE SURFACE MAIN FIELD, EPOCH 1945 




FIG. 4 -CURRENT-FUNCTION IN I0 7 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 3000 KM WITHIN EARTH TO REPRO- 
DUCE SURFACE MAIN FIELD, EPOCH 1945 



31 




FIG. 5— CURRENT-FUNCTION IN I0 6 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH ZERO WITHIN EARTH TO REPRODUCE 

RESIDUAL (NON-DIPOLE PART) OF MAIN FIELD, EPOCH 1945 




FIG. 6— CURRENT-FUNCTION IN I0 6 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 1000 KM WITHIN EARTH TO REPRO- 
DUCE RESIDUAL (NON-D/POLE PART) OF MAIN FIELD, EPOCH 1945 

32 




FIG. 7-CURRENT-FUNCTION IN I0 6 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 2000 KM WITHIN EARTH TO REPRO- 
DUCE RESIDUAL (NON-D/POLE PART) OF MAIN FIELD, EPOCH 1945 




FIG. 8- CURRENT-FUNCTION IN IG 6 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 3000 KM WITHIN EARTH TO REPRO- 
DUCE RES /DUAL (NON-D/POLE PART) OF MAIN FIELD, EPOCH 1945 



33 



CHAPTER m 
GEOMAGNETIC SECULAR CHANGE AND ITS ANALYSIS 



1. Introductory remarks. --Among previous analyses 
of secular change there are those of Carlheim-Gyllen- 
skold and Bartels [3]. 

Carlheim-Gyllenskold expressed the potential at 
epochs 1787, 1700, and 1600, as sums of terms of the 
form 



.t m/ 
V n /a 



C sin(mX + e„ )P„ 
n x n ' n 



where C n was supposed approximately constant, and 
e n m = y n m + Pn m t, where t is the time in years. He 
supposed the period of revolution of field about the axis 
of rotation, T n m to be 27r/p n m , and found Tj 1 =3,147, 
T2 1 = 1,381, and T 2 2 = 454 years. 

Bartels analyzed the change in the main field at 14 
observatories for the period 1902 to 1920, using harmon- 
ics up to and including the degree n = 2. 

Chapman and Bartels [3] examined the coefficients 
from these two analyses, and some particulars of Table 
9, Chapter n, and suggested 

(a) The spherical harmonic series for the secular 
variation converges much more slowly than that of the 
main field. The predominance of the first-order term, 
so conspicuous in the main field, does not appear in the 
secular variation. 

(b) Gyllenskold's phase formula is not valid, nor the 
isomagnetic charts drawn by Fritsche, for epochs ex- 
tending back as far as A.D, 1000, based on extrapolations 
of similar formulas. 

(c) The apparent decrease in the Earth's magnetic 
moment, by about 1/1000 of its whole value per annum, 
which is indicated by a comparison between the results 
of analyses of the main field at different epochs, appears 
also in Bartels' secular -variation analysis; he found the 
value of +42y for the annual change of gf (which in 
1922 was about -31,500y), or rather more than 0.1 per 
cent, and the percentage change in other harmonics much 
greater . 

(d) While the main field may be regarded as a com- 
bination of a planetary field (the dipole field) and of weak- 
er regional fields, the secular variation appears to have 
no outstanding part of planetary character; it consists 
largely of six regional changes which cannot easily be 
represented by arspherical harmonic series. 

Elsasser [11] in his most recent paper on the origin 
of secular change finds a value Tj 1 of 3,000 years, using 
all available data except those of Table 9. 

The validity of the estimates of such periods, using 
data over a relatively short period of time, is of course 
difficult to assess. Our colleague, E. A. Johnson, hopes 
to verify the possible existence of such periodicities from 
measurements on the remanent magnetizations of ancient 
varves, the yearly deposits preserved in nature and 
formed at the bottom of glacial lakes. In this way the 
periodicities shown over periods as long as 25,000 years 
may be forthcoming. 

Our suggestions would be similar to those of Chap- 
man and Bartels. In our preparation of isoporic_charts 
of current epoch, we have experienced considerable 



difficulty in extrapolating secular change five ye,ars into 
the future, and we believe that extrapolation into the past 
is no less difficult and uncertain. 

The results of spherical harmonic analyses of the 
charts for 1912.5, 1922.5, 1932.5, and 1942.5 are included 
here. Isoporic values for epochs 1932.5 and 1942.5 were 
computed, using automatic machines, to estimate values 
for various heights in the atmosphere. Computed values 
of V are provided for each of the four epochs, and for the 
vertical gradients of X, Y, and Z. Finally, current 
functions, for each of the four epochs separately, are 
shown in mapped form for the same depths as used in 
similar calculations for the main field. 

Finally, the probable depth at which secular change 
originates within the Earth is discussed. The rapid 
changes in current pattern in each ten-year interval is 
noted, and a few tentative comments are ventured re- 
specting their bearing on the structure of the Earth's 
interior. 

2. Data analyzed. --Tables 33 to 40 give values of X 
and Y at four epochs, which comprise the data for our 
analyses. Due to the use of machine techniques in anal- 
ysis, the procedures were for convenience the same as 
those used for the main field. There were thus obtained 
48 coefficients of spherical harmonic terms. 

Table 41 lists the coefficients found for X and Y 
separately, epoch by epoch. It can scarcely be doubted 
that some of these are lacking in significance, especially 
the small terms of higher degree. However, the system- 
atic changes with epoch seem fairly regular, and the fit 
of the original data, given in Tables 42 to 49, seems sat- 
isfactory. 

Tabular values of Z at each epoch, computed from 
adopted coefficients of X and Y, have been given in the 
preceding volume in Tables 12 to 15 [1] where they were 
successfully used in construction of isoporic charts in Z. 

3. Secular -change values at various heights. - -Tables 
50 to 79 list computed values of X, Y, and Z at five ele- 
vations in and beyond the atmosphere, using the 48 coef- 
ficients as needed, for epochs 1932.5 and 1942.5. These 
permit adjustment of main field charts for 1945 to other 
epochs not too remote. As would be expected, higher 
order harmonics yielded insignificant contributions to 
the calculated change at greater heights. Table 80 gives 
an experimental calculation of Z at a depth of 1000 km. 

4. Secular change in V. --Tables 81 to 84 list the 
computed values of V at four epochs, and Table 85 gives 
the value of V for the residual field at epoch 1942.5. 
These are interesting because they make possible quali- 
tative inferences respecting the internal distribution of 
sources of secular change, in conjunction with values of 
Z, and, say, of the vertical gradient of Z. 

5. The vertical derivatives of field components of 
secular change at various epochs. --Tables 86 to 97 give 
the space rate of change in a vertical direction of the 
field components X, Y, and Z of secular change at four 
epochs. These distributions were roughly mapped, in 
the hope that the gradients of secular change might re- 
flect some shallow -seated effects related to crustal 



35 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



features of the Earth. As Vening Meinesz [13] has point- 
ed out, there seem to exist suggestive similarities in 
patterns of geomagnetic effects and those of crustal 
stresses which warrant further examination. 

Tables 98 to 100 give values corresponding to those 
in Tables 86 to 97 but are for the changes in residual 
field for epoch 1942.5. We were not successful in deduc- 
ing any important result from these tables. We give the 
values for the possible use of future investigators. 

It might be mentioned in passing that the computed 
values appear small over the Pacific basin, where a gra- 
nitic layer of the Earth's crust has not been found. 

Table 101 lists the spherical harmonic coefficients 
found from our new charts as well as for previous analy- 
ses. 

6. Current functions at various depths reproducing 
secular change at the surface of the ground. --Figures 9 
to 24 show the current functions at depths 0, 1000, 2000, 
and 3000 km, for four epochs, estimated in a manner 
similar to that previously used for the main field. They 
give the yearly change in the current functions of the 
main field at various epochs. 

Those for the residual field are shown in Figures 25 
to 28, for 1942.5; these may be compared with Figures 5 
to 8, presented in Chapter n, for the residual part of the 
main field. 

As with the main field itself, the yearly changes in 
current rapidly increase in complexity with increasing 
depth. Again the current pattern given for depth 3000 km 
is likely to be much too simple. We may safely infer 
that a major part of secular change does not originate in 
a region of greater depth, and that a more modest depth 
of region is therefore probable, by virtue of greater 
simplicity in concepts. These results accord well with 
those of McNish [14] who found that the surface residual 
field and secular change could be represented rather well 
by a number of radial dipoles at depth (a/2). 

The rapid changes in current pattern and intensity 
per decade call for special attention. They show that the 
Earth's interior is susceptible of rapid change with time 
in its attributes. The current density varies rapidly dur- 
ing the course of a decade. Thus, there occur consider- 
able changes in electromotive driving forces in only ten 
years, if we regard secular change as due to electric 



currents. Alternatively, the electric conductivity at high 
pressures might be exceedingly high, even approaching 
superconductivity. In this way small changes in driving 
force could produce great change in current. 

However, there is another aspect to trouble us. The 
pattern change in ten years is great. Are we then to sup- 
pose that weak electromotive forces, such as thermo- 
electric forces, can redistribute themselves with great 
rapidity? This does not appear reasonable in view of the 
now ancient status of the physical experiment which pro- 
duces the magnetic field of the Earth. We have in our 
hypotheses adopted the ultimate favorable environment 
for the flow of huge electric currents as a consequence 
of feeble driving forces, but our first attempt to arrive 
at a check results in a need for a new hypothesis perhaps 
as revolutionary as the first. 

We note that the changes with time in current pattern 
are highly systematic as well as rapid. They may arise 
therefore from gradually fluctuating processes, which 
began at some time during the past history of the Earth, 
and are still continuing. We know of no such processes, 
however, now going on with sufficient rapidity within the 
Earth's crust. Mountain building and continental changes 
take place at a slow rate compared with fluctuations 
which must account for secular change. The latter ap- 
parently occur, with some irregular tendencies, in cycles 
of a few hundred years' period, as judged by available ob- 
servations and from measurements of varves [15]. 

There is real need for studies of the physical prop- 
erties of earth materials at high pressures. These would 
permit discussion of some aspects of the origin of the 
main field and its secular change in terms of particulars 
within our experience. There is also need for further 
studies such as those on the magnetization of varves. 
These yield dated information over thousands of years 
where their results can be properly interpreted. It would 
also seem that varve investigations might well be supple- 
mented by similar studies of such materials as suitable i 
sedimentary rocks, in order that indications might be 
forthcoming, even though not so well dated, respecting 
long-term attributes of the variation of the main field. J 
It would also seem of value to extend studies of possible 
stress-distributions within the Earth's interior. 



TABLES 33-101 



Table Page 

33-36. Values of secular change in north component (X) of magnetic field intensity for 

1912.5, 1922.5, 1932.5, and 1942.5 38 

37-40. Values of secular change in east component (Y) of magnetic field intensity for 

1912.5, 1922.5, 1932.5, and 1942.5 40 

41. Values of spherical harmonic coefficients of secular change in north (X) and east (Y) 

components of magnetic field intensity 42 

42-45. Observed minus computed values of secular change in north component (X) of mag- 
netic field intensity for 1912.5, 1922.5, 1932.5, and 1942.5 43 

46-49. Observed minus computed values of secular change in east component (Y) of magnetic 

field intensity for 1912.5, 1922.5, 1932.5, and 1942.5 45 

50-54. Computed values of secular change in north component (X) of magnetic field intensity 

for 1932.5 at heights 100, 300, 500, 1000, and 5000 km 47 

55-59. Computed values of secular change in north component (X) of magnetic field intensity 

for 1942.5 at heights 100, 300, 500, 1000, and 5000 km 49 

60-64. Computed values of secular change in east component (Y) of magnetic field intensity 

for 1932.5 at heights 100, 300, 500, 1000, and 5000 km 52 

65-69. Computed values of secular change in east component (Y) of magnetic field intensity 

for 1942.5 at heights 100, 300, 500, 1000, and 5000 km 54 

70-74. Computed values of secular change in vertical component (Z) of magnetic field 

intensity for 1932.5 at heights 100, 300, 500, 1000, and 5000 km 57 

75-79. Computed values of secular change in vertical component (Z) of magnetic field 

intensity for 1942.5 at heights 100, 300, 500, 1000, and 5000 km 59 

80. Computed values of secular change in vertical component (Z) of magnetic field intensity 

for 1932.5 at depth 1000 km 62 

81-84. Computed values of secular change in magnetic potential (V), main field, for 1912.5, 

1922.5, 1932.5, and 1942.5 62 

85. Computed values of secular change in magnetic potential (V), residual field, for 1942.5 . . 64 
86-89. Computed values of secular change in the vertical gradient of north component of 

magnetic field intensity (8X/dr), main field, for 1912.5, 1922.5, 1932.5, and 1942.5 .... 65 
90-93. Computed values of secular change in the vertical gradient of east component of mag- 
netic field intensity (dY/dv), main field, for 1912.5, 1922.5, 1932.5, and 1942.5 67 

94-97. Computed values of secular change in the vertical gradient of vertical component of 

magnetic field intensity (3Z/3r), main field, for 1912.5, 1922.5, 1932.5, and 1942.5 .... 69 
98-100. Computed values of secular change in the vertical gradient of north component 

(8X/9r), east component (6Y/dr), and vertical component (dZ/dr), residual field, 

for 1942.5 71 

101. Spherical harmonic coefficients for the average annual secular variation 72 



37 



Table 33. Values of secular change in north component (X) of magnetic field intensity for 1912.5 

expressed in units of 10-6 CGS per year 



Geographic 
east 












Geograph 


ic colatitude in 


degree 


3 






longitude 
in degrees 


10 


20 


30 


40 


50 




60 


70 


80 


90 


30 


- 170 


_ 


270 


_ 


400 


_ 


36 


_ 


170 




20 


16 


100 


50 


60 


- 26 


- 


380 


- 


600 


- 


710 


_ 


610 


- 


34 


-110 


40 


- 10 


90 


- 29 


- 


390 


- 


52 


- 


590 


- 


32 


- 


30 


310 


37 


2 2 


120 


- 25 


- 


34 


- 


400 


- 


31 


- 


80 




R 


15 


10 


1 


150 


- 170 


- 


24 


- 


25 


- 


110 


_ 


90 




60 


110 


10 


70 


180 


40 


- 


130 


- 


100 


- 


80 


- 


110 


_ 


40 


00 


20 


- 1 


2 10 


70 


- 


10 




10 


- 


120 


- 


22 


- 


260 


- 27 


- 2 R 


- 31 


24 


150 




90 




90 


- 


12 


- 


340 


- 


4 6 


- 40 


- 1 R 


- 16 


27 


22 




22 




190 


- 


12 


- 


57 


- 


9 8 


- R5 


- 5 4 


50 


30 


230 




330 




34 




40 


- 


47 


_ 


9 00 


- 1 4 


- 600 


00 


33 


130 




170 




22 




27 




29 




12 


00 


- 110 


- 2 3 


360 


20 


- 


30 


- 


10 




100 




25 




36 


33 


15 


70 




Geographic 
east 












Geograph 


ic colatitude in 


degree 


3 






longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


- 24 


_ 


4 6 


_ 


730 


_ 


60 


_ 


32 




00 


270 


70 




60 


- 16 


- 


24 


- 


30 


- 


19 




13 




52 


58 


40 




90 


5 


- 


200 


- 


63 


- 


62 


- 


17 




310 


23 


- 310 




120 


- 13 


- 


310 


- 


4 80 


- 


38 


- 


13 




RO 


- 17 


- 57 




15 


- 150 


- 


27 


- 


33 


- 


22 


- 


19 


- 


2 9 


- 43 


- 52 




18 


- 25 


- 


4 4 


- 


4 2 


- 


24 


_ 


29 


- 


40 


- 44 


- 2 2 




210 


- 4 3 


- 


55 


- 


4 5 


- 


27 


- 


50 


- 


70 


- 14 


20 




24 


- 35 


- 


55 


- 


400 


- 


210 


- 


40 




30 


14 


16 




27 


14 


- 


60 


- 


2 3 


- 


34 


- 


22 


- 


13 


80 


370 




300 


26 




10 


- 


25 


- 


54 


- 


58 


- 


37 


30 


36 




330 


- 300 


- 


45 


- 


63 


- 


9 8 


-112 


- 


73 


- 23 


25 




360 


- 24 


- 


44 


- 


710 


-115 


- 


92 


- 


55 


- 18 


130 




Tabl 


e 34. Van 


les 


of secu 


ar 


change : 


n north component (X) of magnetic field intensity for 1922.5 










expressed in units of 1C 


1-0 CGS 


per year 








Geographic 
east 












Geograph 


c colatitude in 


degree: 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


- 230 


_ 


31 


_ 


39 


_ 


330 


_ 


160 




30 


80 


90 


90 


6 


- 34 


- 


390 


- 


600 


- 


6 2 


- 


4 4 


- 


180 


60 


200 


50 


9 


- 320 


- 


400 


- 


56 


- 


4 5 


- 


25 


_ 


40 


18 


350 


260 


12 


- 240 


- 


370 


- 


39 


- 


29 


- 


14 




10 


12 


130 


6 


15 


- 13 


- 


300 


- 


2 80 


- 


190 


- 


80 







10 


10 


- 110 


18 


20 


- 


130 


_ 


150 


- 


14 


- 


16 


_ 


170 


- 200 


- 22 


- 200 


210 


180 




40 


- 


70 


~ 


19 


- 


280 


- 


34 


- 360 


- 36 


- 32 


2 4 


24 




110 




10 


- 


18 


- 


32 


- 


45 


- 46 


- 42 


- 350 


27 


29 




22 




10 


- 


150 


- 


500 


- 


6 80 


- 63 


- 510 


- 310 


3 


2 3 




330 




280 


*• 


110 


- 


29 


- 


62 


- 680 


- 47 


- 160 


3 3 


70 




200 




23 




24 




25 




160 


90 


10 


- 210 


360 


- 120 


- 


70 




20 




90 




210 




33 


300 


110 


70 




Geographic 
east 












Geograph 


c colatitude 


! in 


degree; 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


- 33 


_ 


62 


_ 


87 


_ 


64 


_ 


32 




50 


140 


80 




6 


- 210 


- 


4 80 


- 


6 5 


- 


47 


- 


100 




31 


330 


50 




9 


110 


- 


22 


- 


610 


- 


62 


- 


300 




20 


30 


- 310 




12 


40 


- 


150 


- 


34 


- 


410 


- 


21 


- 


70 


- 28 


- 54 




15 


- 16 


- 


19 


- 


25 


- 


23 


- 


180 


- 


29 


- 43 


- 57 




18 


- 200 


- 


24 


- 


33 


- 


360 


- 


300 


- 


34 


- 42 


- 35 




2 10 


- 30 


- 


330 


- 


410 


- 


400 


- 


24 


- 


13 


- 190 


90 




2 4 


- 36 


- 


390 


- 


390 


- 


35 


- 


2 60 


- 


60 


80 


180 




27 


- 24 


- 


370 


- 


49 


- 


510 


- 


37 


- 


230 


80 


400 




30 


- 12 


- 


320 


- 


50 


- 


77 


- 


85 


- 


57 


- 130 


350 




33 


- 380 


- 


53 


- 


74 


- 


980 


- 


1180 


- 


83 


- 29 


24 




36 


- 280 


- 


52 


- 


77 


-104 


— 


82 


- 


48 


- 23 


130 





38 



Table 35. Values of secular change in north component (X) of magnetic field intensity for 1932.5 

expressed in units of 10-6 CGS per year 



Geographic 
east 












Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


^0 


80 


90 


3 


- 400 


— 


470 


_ 


42 


«. 


280 


_ 


20 




200 


26 


50 


- 200 


6 


- 52 


- 


580 


- 


510 


- 


330 


- 


60 




200 


330 


250 


60 


90 


- 430 


- 


4 80 


- 


36 


- 


130 




12 




320 


46 


4 4 


39 


120 


- 300 


- 


34 


- 


21 


- 


50 




60 




12 


180 


15 


- 10 


15 


- 170 


- 


200 


- 


180 


- 


80 




10 




80 


14 


60 


- 12 


18 


20 


- 


40 


- 


90 


- 


50 




10 




60 


40 


20 


- 12 


210 


160 




60 




20 


- 


40 


- 


80 


- 


130 


- 160 


- 210 


- 270 


3 4 


260 




170 




90 


- 


80 


- 


200 


- 


320 


- 40 


- 400 


- 39 


27 


350 




280 




13 


- 


12 


- 


52 


- 


72 


T 64 


- 410 


- 280 


300 


280 




32 




280 




30 


- 


270 


- 


480 


- 47 


- 310 


- 15 


33 


80 




160 




23 




260 




21 




150 


16 


10 


- 26 


360 


- 20 


- 


17 


•* 


40 




60 




250 




43 


31 


30 


- 230 




Geographic 
east 












Geographi 


c colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


- 47 


_ 


74 


_ 


83 


_ 


550 


_ 


25 




70 


23 


280 




60 


- 19 


- 


5 4 


- 


610 


- 


42 


- 


12 




240 


150 


- 14 




90 


90 


- 


25 


- 


600 


- 


590 


- 


270 


_ 


20 


- 15 


- 500 




120 


10 


- 


60 




40 


- 


50 




20 


_ 


90 


- 29 


- 570 




150 


- 24 


- 


180 


- 


12 


- 


30 


- 


110 


_ 


23 


- 370 


- 460 




18 


- 330 


- 


38 


- 


340 


- 


210 


- 


260 


_ 


33 


- 310 


- 22 




210 


- 37 


- 


500 


- 


53 


- 


43 


- 


290 


_ 


14 


90 


50 




24 


- 4 10 


- 


51 


- 


55 


- 


580 


- 


410 


_ 


19 


19 


410 




27 


- 210 


- 


25 


- 


44 


- 


650 


- 


580 


_ 


39 


90 


670 




300 


80 


- 


190 


- 


49 


- 


740 


- 


830 


_ 


610 


- 150 


650 




330 


- 47 


- 


6 3 


- 


75 


- 


870 


_ 


870 


_ 


630 


- 23 


40 




36 


- 500 


- 


69 


- 


83 


— 


79 


- 


570 


- 


35 


- 100 


340 





Table 36. Values of secular change in north component (X) of magnetic field intensity for 1942.5 

expressed in units of 10-6 CGS per year 



Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


- 17 


- 260 


- 24 


_ 


80 




17 




360 


370 


210 


10 


6 


- 29 


- 310 


- 170 


- 


90 




180 




380 


50 


57 


460 


9 


- 310 


- 20 


90 




11 o 




35 




53 


560 


520 


4 6 


120 


- 22 


- 10 


40 




32 




21 




25 


22 


180 


16 


15 


- 14 


5 


90 




5 




5 




70 


60 


40 


20 


18 


40 


2 


12 




70 




20 


- 


30 


40 


70 


- 14 


210 


8 


4 


110 




60 


- 


20 


- 


100 


- 170 


- 23 


- 32 


2 4 


210 


120 


19 




130 




20 


- 


10 


- 18 


- 280 


- 380 


27 


31 


24 


24 




130 







- 


130 


- 240 


- 34 


- 370 


300 


30 


28 


34 




280 




23 




110 


130 


40 


60 


33 


12 


14 


320 




44 




530 




390 


18 


40 


- 130 


36 


20 


30 


70 




22 




4 4 




45 


23 


60 


- 110 




Geographic 
east 








Ge 


ographi 


C CO 


latitude 


in degrees 








longitude 
in degrees 


100 


110 


120 




130 




140 




150 


160 


170 




























3 


- 260 


- 59 


- 6 3 


— 


27 


«. 


70 




90 


260 


50 




6 


170 


- 17 


- 46 


- 


500 


- 


32 




60 


230 


- 27 




9 


32 


30 


- 2 8 


- 


500 


- 


4 60 


- 


90 


80 


- 54 




12 


150 


15 


22 


- 


190 


- 


36 


- 


22 


80 


- 72 




15 


20 


60 


2 


- 


30 


- 


150 


- 


250 


- 18 


- 4 80 




18 


- 210 


- 25 


- 23 


- 


19 


- 


21 


- 


130 


10 







21 


- 39 


- 45 


- 390 


- 


300 


- 


21 


- 


40 


220 


500 




2 4 


- 470 


- 57 


- 62 


- 


47 


- 


200 




40 


31 


860 




27 


- 34 


- 40 


- 54 


- 


67 


- 


54 


- 


240 


26 


980 




30 


- 200 


- 42 


- 620 


- 


89 


- 


77 


- 


51 


20 


870 




3 3 


- 29 


- 4 60 


- 74 


- 


83 


- 


700 


- 


45 


30 


65 




360 


- 25 


- 50 


- 64 


- 


54 


- 


40 


** 


160 


100 


370 





39 



Table 37. Values of secular change in east component (Y) of magnetic field intensity for 1912.5 
expressed in units of 10*6 CGS per year 



Geographic 
east 










Geographi 


c colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


17 3 


16 1 




31 




42 




580 




70 


770 


85 


89 


60 


4 


9 


- 


10 


- 


2 









10 





30 


- 110 


90 


4 


- 14 9 


- 


310 


- 


50 1 


- 


62 


- 


66 


- 69 1 


- 610 


- 4 6 


12 


- 10 9 


- 17 


- 


2 8 


- 


28 9 


_ 


26 


- 


23 


- 150 


6 


2 


150 


- 19 


- 17 


- 


26 


- 


24 


- 


19 1 


- 


12 


50 


- 12 


- 17 


180 


- 25 3 


- 23 1 


- 


190 


- 


10 


- 


30 




40 


70 


100 


110 


2 10 


- 213 


- 12 


- 


10 




40 




90 




14 


17 


150 


130 


24 


9 2 


70 


- 


70 


- 


2 




70 




17 


29 1 


35 


2 8 


2 70 


1 7 


70 


- 


18 


- 


18 


- 


70 




50 


210 


44 


4 4 


3 


13 8 


12 




80 


- 


2 


- 


25 1 


- 


57 


- 82 


- 97 


-1 01 


3 3 


25 3 


33 9 




37 




2 8 9 




110 


- 


14 


- 4 5 


- 67 


- 66 


3 60 


25 9 


31 9 




4 6 




53 1 




55 




560 


59 1 


58 


500 




Geographic 
east 










Geographic colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


HO 


150 


160 


170 




30 


9 6 1 


97 1 




102 




800 




5 80 




29 


- 12 9 


- 53 




60 


- 200 


- 3 8 


- 


32 


- 


18 


- 


17 


_ 


19 


- 380 


- 62 2 




90 


- 4 4 


- 52 


- 


56 


- 


54 


- 


571 


- 


55 


- 4 5 


- 4 6 1 




12 


1 


13 




110 




10 


- 


19 


_ 


19 


91 


4 




15 


- 17 


- 15 


- 


110 


- 


4 









80 


25 1 


4 2 




180 


110 


13 




13 




15 




24 




31 


52 


72 




2 10 


19 


22 




270 




33 9 




42 




4 9 


57 9 


74 9 




2 4 


13 


8 




70 




9 




18 




28 


380 


53 




2 70 


25 


4 


- 


13 


- 


23 


- 


19 


_ 


8 


50 


23 




3 


- 92 


- 79 1 


- 


710 


_ 


6 2 


- 


52 


_ 


37 


- 26 9 


8 1 




3 3 


- 4 8 


- 34 1 


- 


24 9 


- 


17 


_ 


19 


_ 


22 


- 289 


- 40 3 




3 60 


45 


4 3 




50 




6 2 




35 




14 


- 12 


- 513 




Tal 


ale 38. Va 


ues of secu 


lar change 


in east con- 


pon 


ent (Y) of ] 


nagnetic 


field intensity for 1922.5 








e 


xpressed in 


units of 10 


-6 CGS 


per 


year 








Geographic 
east 










Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


16 1 


25 1 




380 




48 1 




590 




6 5 


66 


740 


82 


60 


2 9 


2 9 


_ 


40 


- 


70 


- 


60 


_ 


50 


40 


- 12 


- 270 


90 


- 17 9 


- 19 9 


- 


25 


- 


341 


- 


44 


_ 


46 


- 47 


- 380 


- 200 


12 


- 311 


- 33 


- 


31 


- 


280 


- 


22 1 


_ 


191 


- 140 


70 


2 


150 


- 311 


- 310 


- 


230 


- 


16 


- 


13 1 


- 


110 


- 100 


90 


9 


IflO 


- 19 


- 219 


- 


16 


- 


7 


- 


10 




30 


40 


70 


90 


2 10 


- 10 9 


- Ill 


- 


90 


_ 


40 









50 


12 


16 


22 


240 


17 


7 9 


- 


130 


- 


170 


- 


140 


- 


50 


50 


18 


23 


2 70 


8 1 


2 9 


- 


13 


- 


21 9 


- 


15 


_ 


40 


12 


310 


30 


30 


21 9 


16 1 




80 




40 


- 


101 


_ 


4 80 


- 72 


- 870 


- 92 


3 3 


34 


38 9 




380 




31 




191 




30 


- 190 


- 35 


- 390 


3 60 


31 1 


40 9 




570 




62 1 




62 




600 


560 


510 


4 80 




Geographic 
east 










Geographi 


; colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


82 


870 




900 




73 




470 




16 


- 231 


- 63 3 




60 


- 431 


- 530 


- 


570 


- 


52 


- 


4 8 1 


- 


4 4 


- 42 1 


- 63 3 




90 


- 210 


- 22 


- 


230 


- 


27 9 


- 


37 


- 


4 7 


- 4 30 


- 501 




120 


80 


17 




100 


- 


50 


- 


16 


- 


22 


- 140 


17 




15 


90 


40 


- 


40 


- 


50 




7 9 




130 


23 1 


380 




ISO 


160 


18 




210 




24 




31 




44 


57 9 


76 




2 10 


280 


30 




330 




35 




42 9 




52 


649 


82 9 




24 


22 


23 




249 




26 




28 




380 


4 80 


62 8 




2 70 


14 


2 


- 


170 


- 


17 


- 


12 


- 


20 


11 1 


31 1 




3 


- 84 


- 79 1 


- 


700 


~ 


610 


- 


57 1 


- 


410 


- 23 1 


81 




3 3 


- 301 


- 23 


«. 


130 


- 


80 


- 


7 9 


- 


180 


- 371 


- 43 2 




3 60 


400 


380 




46 




560 




370 




170 


- 301 


- 66 2 





40 



Table 39. Values of secular change in east component (Y) of magnetic field intensity for 1932.5 

expressed in units of 10-6 CGS per year 



Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


28 8 


301 


29 




411 




57 




530 


53 


52 


4 5 


60 


5 8 


4 1 


60 


- 


70 


- 


9 


- 


110 


- 12 


- 22 


- 390 


90 


- 17 9 


- 219 


- 22 


- 


280 


- 


350 


- 


35 


- 32 


- 231 


- 13 


12 


- 311 


- 33 9 


- 28 


- 


24 


- 


110 


- 


2 


30 


110 


80 


15 


- 38 


- 33 


- 27 


- 


23 


_ 


19 1 


- 


150 


- 110 


40 


6 


18 


- 311 


- 26 9 


- 210 


- 


14 9 


- 


10 1 


- 


40 


30 


10 


14 


210 


- 213 


- 18 1 


- 12 


- 


79 


_ 


5 







70 


16 


23 


2 4 


- 10 9 


- 12 


- 17 


- 


20 1 


- 


110 




2 


90 


110 


16 


2 70 


4 


2 


- 18 


- 


21 


- 


90 


- 


1 


200 


110 


2 


3 


24 2 


19 9 


12 




4 


_ 


110 


- 


33 9 


- 630 


- 880 


- 85 


3 3 


36 9 


4 3 


42 




35 




25 1 




16 1 


30 


- 100 


- 18 


3 60 


38 


50 9 


55 




601 




590 




52 


51 


4 8 


4 3 




Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


380 


37 


42 




33 9 




210 




100 


- 301 


- 72 




60 


- 4 4 


- 56 


- 670 


- 


590 


- 


411 


- 


38 


- 4 8 


- 714 




90 


- 14 


- 19 


- 23 1 


- 


290 


- 


35 9 


- 


37 


- 380 


- 43 2 




120 


12 


23 


330 




30 




70 


- 


14 


7 9 


1 7 




15 


70 


2 


70 




10 1 


- 


20 




8 


26 


4 4 3 




180 


90 


80 


100 




20 




35 




510 


6 8 1 


812 




2 10 


270 


32 


370 




43 9 




53 1 




62 


68 1 


84 1 




24 


150 


16 


12 




90 




14 




34 


54 1 


69 1 




2 70 


5 


80 


- 16 1 


- 


26 


- 


25 


- 


18 


16 1 


40 9 




3 


- 77 


- 69 1 


- 62 


- 


55 


- 


510 


_ 


39 


- 26 


17 




3 3 


- 20 


- 130 


40 


- 


2 


- 


7 9 


- 


19 


- 38 9 


- 4 4 9 




3 60 


42 


44 1 


4 80 




44 




350 




130 


- 319 


- 72 





Table 40. Values of secular change in east component (Y) of magnetic field intensity for 1942.5 
expressed in units of 10-6 CGS per year 



Geographic 
east 








Geographic co 


latitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


19 


26 9 


24 




33 




39 




370 


37 


32 


25 


60 


5 2 


12 


10 


- 


30 


- 


80 


- 


140 


- 22 


- 25 


- 40 


90 


- 13 1 


7 9 


- 150 


- 


26 


- 


33 9 


- 


33 9 


- 29 1 


- 200 


- 130 


12 


- 37 1 


- 281 


- 25 


- 


28 


- 


21 


- 


80 


20 


12 


16 


15 


- 340 


- 33 9 


- 27 


- 


24 


- 


21 


- 


150 


- 12 


- 100 


60 


1 80 


- 38 3 


- 24 


- 18 


- 


12 


- 


70 




10 


40 


7 


100 


2 10 


- 17 9 


- 14 9 


70 


- 


5 


- 


10 




50 


130 


21 


26 


2 4 


9 8 


- 12 


- 13 


- 


13 1 


- 


12 


_ 


80 


2 


3 


110 


2 70 


6 9 


50 


- 10 


_ 


12 


- 


20 




30 


60 


70 


10 


3 


219 


12 


80 


- 


2 


_ 


15 


- 


30 9 


- 541 


- 610 


- 62 


3 3 


34 


31 


34 




27 1 




14 




5 


10 


- 110 


- 12 


3 60 


311 


35 1 


410 




4 8 1 




510 




4 8 


4 3 


33 


25 




Geographic 
east 








Geographic 


: colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


200 


22 


230 




90 


_ 


6 1 


_ 


21 


- 47 1 


- 78 3 




60 


- 55 


- 630 


- 710 


- 


77 


- 


700 


- 


590 


- 62 9 


- 70 3 




90 


- 16 


- 210 


- 27 9 


- 


35 


- 


4 4 


- 


4 9 


- 45 9 


- 32 8 




12 


21 


29 1 


32 




110 


- 


7 9 


- 


70 


9 


32 2 




15 


2 


70 


14 




210 




33 




26 


380 


639 




18 


14 


190 


24 9 




35 




53 1 




75 


90 1 


1019 




210 


301 


37 


4 3 




510 




601 




700 


86 


9 10 




2 4 


170 


160 


14 




170 




21 9 




25 


38 9 


48 9 




2 70 


- 110 


- 17 


- 24 9 


- 


33 9 


- 


30 


- 


22 


7 9 


9 8 




3 


- 580 


- 53 


- 4 4 


- 


42 


- 


400 


- 


36 


- 37 1 


- 57 




3 30 


- 10 


2 


80 




80 


- 


2 


- 


120 


- 25 1 


- 6 80 




3 60 


210 


280 


36 




29 




17 







- 19 9 


- 67 4 





41 





Table 41. Values of spherical harmonic coefficients of secular change in north 
and east (Y) components of magnetic field intensity 
expressed in units of 10-7 CGS per year 


(X) 




n 


An" 


m 


1912.5 


1922.5 


1932.5 


1942.5 




X 


Y 


X 


Y 


X 


Y 


X 


Y 




1 

9. 
3 

a 

5 
6 


247 

-138 5 

169 5 

1005 

-2 38 4 

6 8 4 




2 83 9 

-2 06 1 

199 5 

105 4 

- 1 94 6 

76 3 




2 29 8 

-2 815 

125 8 

193 5 

-103 1 

4 




919 

-3 57 4 

53 3 

182 5 

-114 6 

139 5 




1 

1 
1 
1 

1 

1 


1 
3 
3 
4 
5 
6 


9 2 

31 S 

-149 3 

16 8 4 

- 1 79 4 

6 6 5 


103 

- 83 2 

-1810 

1617 

- 415 
115 1 


57 5 

30 9 

-2 419 

144 1 

- 6 1 

6 7 


160 

4 8 

-2 036 

109 8 

-127 6 

23 6 


67 
66 1 

- 2 4 5 4 
136 1 

- 45 8 
25 5 


20 2 
- 13 2 
-193 5 

6 3 

-10 6 5 

137 3 


50 2 
- 35 8 
-247 2 

75 2 

11 
5 8 


- 18 7 
4 3 

- 1 91 8 

47 2 
56 

- 14 


3 
2 
2 

?. 


2 
3 
4 
5 

6 


5 14 4 

- 73 3 

- 74 6 
-2 16 4 

52 2 


4 37 1 

8 3 

- 1 39 4 

-184 3 

40 6 


3 25 6 

- 6 3 

- 19 3 

- 1 79 5 

15 8 


3 34 7 

- 54 6 

-127 7 

-116 3 

75 


2 011 
3 8 2 

- 1 8 

- 1 5 9 2 

9 6 


1918 

4 4 

-105 4 

-139 2 

138 5 


- 14 
1302 

- 16 8 

- 66 9 
77 3 


1119 
6 9 9 

- 6O5 

- 88 5 
827 


3 
3 
3 

3 


3 
4 
5 


39 3 9 

- 76 6 
-133 1 
-1017 


4117 

15 2 

- 1 04 7 

-1211 


180 3 

- 7 8 7 

- 516 
-126 6 


2 6 4 7 
26 3 

- 6 6 2 

- 7 8 5 


76 9 
70 1 

- 23 1 

- 76 9 


112 
64 7 

- 4 5 

- 57 4 


- 37 6 
14 6 5 

19 2 

- 57 5 


42 4 
84 7 

- 38 3 

- 29 1 


4 

4 
4 


4 

5 
6 


2 29 1 

- 2 1 7 4 

76 


164 8 

-132 8 

4 15 


129 3 

- 1 07 7 
57 3 


150 8 

- 1 1 3 

56 5 


163 2 

- 1 3 2 

47 2 


105 3 

- 87 6 

104 3 


83 5 

- 10 9 

712 


127 

- 56 1 

44 5 


5 

5 


5 

6 


- 31 3 
3 6 


- 1 99 9 

- 29 2 


-116 4 
- 34 1 


- 92 6 

- 1 4 3 


- 76 5 

- 4 9 3 


-110 9 
- 566 


- 4 8 8 

- 79 5 


- 89 5 

- 83 7 


6 


6 


-14 9 8 




-106 3 




- 1 07 8 




- 10 4 




m 


n 


1912.5 


n m 
B n 

1922.5 


1932.5 


1942.5 




X 


Y 


X 


Y 


X 


Y 


X 


Y 


1 

1 
1 
I 
1 
1 


1 

2 
3 

4 
5 
6 


- 95 3 
-2 14 9 
-2 13 6 

- 26 9 
294 5 

77 6 


- 42 4 
-1567 

- 1 4 8 

- 2 8 1 
4 176 

- 62 9 


-110 2 
-2 83 7 
-156 9 

- 32 6 
2 4 

- 36 2 


- 35 3 

- 2 7 8 3 
-1 37 6 

- 1 4 1 9 
4 17 7 

- 1 7 5 7 


- 87 9 
-3 56 2 
-1537 
-204 8 

2 50 9 

- 53 5 


5 2 
-34 8 3 
-157 6 
-1394 
373 8 
-158 5 


- 24 8 
-396 7 

4 3 2 

-107 9 

130 4 

- 69 4 


51 5 

- 391 9 

- 77 3 
-143 2 

3 39 3 
-1 59 2 


2 
?. 

2 
3 


2 
3 
4 
5 

6 


-337 3 
120 8 

-207 4 

53 2 

114 3 


- 346 2 

64 1 

- 2 5 3 

35 3 
16 8 


-3445 
1371 

-199 8 
92 8 
4 4 2 


-34 12 
4 3 2 

- 2 4 4 

24 6 

127 1 


-2 37 1 
147 1 

- 2 86 6 
116 6 

- 27 1 


- 311 8 
63 5 

-168 8 
20 6 
12 8 


-2 80 1 

1374 

-2 32 4 

99 5 

34 9 


-2 86 1 
110 8 

-2 39 2 

1014 

4 8 1 


3 
3 

3 
3 


3 
4 

5 
6 


-2 89 7 
170 
51 9 
43 3 


-3 73 5 
62 1 
23 4 

33 8 


-292 1 

12 8 6 

- 73 4 

42 6 


-373 8 

14 15 

4 9 

20 3 


- 371 2 
1215 

- 24 5 
29 3 


-395 7 

1302 

- 25 3 

15 9 


-304 3 

120 3 

- 79 3 

302 


-3 22 5 

1172 

7 9 

30 


4 
4 
4 


4 
5 
6 


- 556 

- 319 
93 5 


-1116 

80 
152 2 


- 65 8 

- 13 2 
85 2 


-1380 
115 
59 


-1517 

- 15 3 

57 3 


-123 1 

7 7 

67 6 


- 98 5 
40 2 

- 180 


- 79 8 

- 4 2 9 
215 


5 
5 


5 
6 


118 9 
-14 8 3 


144 3 
- 89 4 


- 32 

- 57 7 


172 4 
- 1 21 7 


144 8 
- 95 9 


1319 
5 


185 1 
- 45 8 


1130 
- 48 8 








47 2 




124 1 




93 3 




73 6 



42 



Table 42. Observed minus computed values of secular change in north component (X) of magnetic field intensity 

for 1912.5 expressed in units of 10-6 CGS per year 



Geographic 
east 








Ge 


ographi 


c colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


3 4 


6 4 


2 6 


_ 


2 6 




7 


_ 


2 


R 


3 


9 


60 


4 


R 3 


2 5 


- 


2 




4 




4 3 


3 2 


2 2 


4 6 


90 


SO 


7 


8 2 




1 




5 9 




P. 


6 4 


2 


4 7 


ISO 


3 6 


2 9 


11 


- 


2 5 







- 


2 6 


3 4 


3 R 


4 


15 


6 4 


4 6 


6 2 




3 R 


- 


2 9 




3 2 


3 2 


4 1 


19 


1 R 


5 


- 1 R 6 


9 6 


- 


5 3 


- 


6 1 




1 


7 


P.O 


2 7 


P 1 


P.7 


5 3 


4 


- 


3 4 


- 


5 2 


- 


5 4 


5 5 


3 6 


1 7 


P. 4 


PI 


13 


9 R 




1 1 




6 


- 


9 


2 8 


R 2 


7 6 


P. 70 


9 


- 10 4 


4 4 




R 4 




7 9 


_ 


4 2 


3 4 


P.O 


14 2 


3 


P. 2 


3 2 


3 7 




3 1 




5 


_ 


2 3 


- 114 


PP. 


7 3 


3 3 


5 


1 9 


7 8 


- 


8 2 




5 


_ 


4 


4 3 


3 5 


4 


3 60 


6 4 


R 


1 1 


- 


2 


- 


1 3 




2 7 


3 5 


2 1 


6 4 




Geographic 
east 








Ge 


ographic colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


5 


50 


- 115 


- 


3 6 




5 




R 9 


R 8 


- PI 7 




60 


P. 9 


6 3 


4 


- 


5 1 




2 




1 R 


14 1 


- 39 8 




90 


7 P 


15 6 


70 


- 


9 9 




9 5 




26 5 


2 2 


- 4 3 9 




IPO 


P. 4 


16 


- 114 


- 


4 P. 




1 




20 3 


6 1 


- 3 5 9 




15 


4 


2 3 


2 6 




1 2 


- 


3 3 


- 


11 R 


- 130 


7 4 




IRQ 


P. 6 


70 


5 




9 R 


- 


6 6 


- 


20 5 


- 14 


22 6 




P. 1 





7 7 


5 5 


- 


5 6 


- 


1 9 


- 


111 


- 10 2 


1 R 9 




24 


?! 1 


9 


9 6 




15 3 




6 R 


- 


9 R 


7 1 


6 2 




PI 


P 1 


7 5 


2 8 




9 6 




12 7 


- 


7 R 


- 143 


R 9 




3 


P. P. 


- 14 6 


3 5 




2 7 




5 1 







47 


7 4 




3 3 


3 3 


6 


10 5 


- 


1 4 


- 


14 4 


- 


3 2 


1 


3 7 




3 60 


1 2 


6 


7 5 


~ 


1 6 R 




4 2 




12 3 


2 8 


- too 





Table 43. Observed minus computed values of secular change in north component (X) of magnetic field intensity 

for 1922.5 expressed in units of 10'6 CGS per year 



Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 




40 




50 


60 


70 


80 


90 


3 


6 9 


4 R 


2 8 




130 


«. 


10 




1 4 


5 1 


2 4 


2 1 


60 


4 3 


6 1 


77 


- 


7 4 




6 




3 5 


9 


9 


4 2 


90 


71 


5 4 


5 9 




2 3 




7 6 




3 4 


15 


5 


4 2 


120 


R 8 


1 5 


8 


- 


4 


- 


1 2 


_ 


1 5 


1 


5 


12 


150 


6 5 


6 4 


4 6 


- 


3 




3 2 




4 1 


10 


3 


2 9 


1 R 


4 8 


7 3 


R 8 


- 


5 6 


- 


2 6 




1 4 





3 8 


33 


2 10 


6 3 


1 3 


13 


- 


4 5 


- 


4 5 


_ 


3 1 


12 


17 


8 


2 4 


1 


9 


R 8 




7 6 




7 4 




1 6 


1 3 


1 6 


4 2 


svo 


3 4 


3 9 


2 




1 2 


- 


4 5 


- 


2 3 


4 6 


1 4 


1 6 


3 


6 5 


8 


1 6 




60 


- 


1 7 


_ 


71 


6 2 


13 


5 


3 3 


4 7 


4 8 


5 


- 


4 1 


- 


15 


_ 


1 2 


4 8 


6 4 


3 2 


3 60 





7 4 


9 1 




1 7 


- 


6 




4 5 


5 2 


14 


R 




Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


no 


130 


140 


150 


160 


170 




3 


3 4 


1 9 


- 12 2 


_ 


1 3 




10 




5 6 


6 1 


- 15 8 




60 


2 


4 4 


14 


- 


1 2 


- 


7 




7 8 


3 


- 24 1 




90 


73 


8 9 


6 


- 


6 3 




5 4 




12 6 


2 4 


- 23 4 




12 


6 


3 2 


5 4 


- 


8 8 




90 




20 5 


1 8 


- 176 




150 


1 5 


5 3 


1 


- 


1 8 




1 1 


- 


4 2 


5 5 


9 6 




1 R 


9 


1 2 


2 4 


- 


4 6 


- 


1 3 


- 


6 5 


- 1 fl 


1 4 




210 


6 


19 


6 4 


- 


4 7 




5 6 




6 


90 


1 




24 


1 7 


1 4 


4 7 




60 




1 3 


- 


9 


6 7 


13 




2 70 


4 


5 1 


1 




70 




8 7 


_ 


77 


8 4 


8 5 




30 


2 9 


- 10 


17 


- 


5 


- 


8 2 


- 


7 3 


3 5 


115 




33 


6 1 


1 4 


86 




6 6 


- 


12 1 


_ 


2 9 


5 8 


12 5 




3 60 


1 8 


4 9 


5 2 


- 


R 




7 5 




136 


9 


3 





43 



Table 44. Observed minus computed values of secular change in north component (X) of magnetic field intensity 

for 1932.5 expressed in units of 10*6 CGS per year 



Geographic 
east 








Geographi 


; colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


2 


4 3 


7 4 


_ 


112 


~ 


7 1 


- 


2 5 


5 


7 4 


3 3 


60 


3 6 


3 2 


5 6 


- 


4 5 




7 




4 7 


2 9 


4 5 


3 8 


PO 


12 3 


2 2 


1 2 




4 5 




6 1 




2 ft 





5 1 


5 5 


12 


12 8 


3 1 


4 7 




5 5 




2 2 


- 


5 


4 7 


7 3 


9 8 


15 


6 6 


1 7 


14 




2 


- 


1 1 


- 


2 9 


1 4 


1 7 


16 


1 P 


4 2 


1 7 


3 1 


- 


1 6 




3 




1 2 


13 


11 


1 5 


RIO 


19 


12 


P. 




2 


- 


6 


- 


1 9 





1 3 


3 3 


2 4 


9 1 


2 9 


4 1 




1 2 




2 5 




1 3 


9 


5 


11 


9,1 


- 1 


3 ft 


7 




1 8 


- 


9 9 


- 


9 3 


1 5 


P 6 


16 


3 


- 12 ft 


15 


90 




6 3 




1 3 


- 


2 2 


2 


1 4 


18 


3 3 


- 117 


12 


5 6 




5 3 


- 


2 7 


- 


6 2 


5 6 


5 9 


7 


3 60 


ft 4 


2 7 


3 8 


- 


1 6 


- 


5 




7 5 


1 1 


5 5 


13 




Geographic 
east 








Geographic co 


latitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


1^0 


3 


2 7 


2 1 


- 106 


_ 


4 6 


- 


ft 7 


- 


70 


5 4 


3 3 




6 


3 7 


19 


5 




2 3 


- 


1 1 




6 8 


77 


- 18 3 




9 


6 6 


6 9 


6 8 


- 


6 6 




ft 3 




167 


2 9 


- 16 7 




ISO 
ISO 


5 


ft 


7 6 


- 


3 8 




8 1 




12 9 


15 9 


6 4 




17 


4 9 





- 


2 9 


- 


10 2 


- 


3 2 


112 


211 




1 ft 


5 3 


18 


1 4 




6 9 


- 


4 4 


- 


9 7 


17 


19 9 




? 1 


P. P, 


2 8 


2 4 




2 6 




2 8 




3 


7 5 


5 5 




? 4 


7 


1ft 


4 3 




1 4 




5 


- 


1 


3 1 


6 5 




2 7 


7 3 


2 7 


1 8 


- 


8 




5 


- 


130 


7 6 


210 




3 


P.O 


1 2 


1 2 




3 3 


- 


1 5 


- 


5 6 


6 1 


280 




3 3 


16 


4 


3 6 




2 7 




4 




1 4 


10 


13 8 




3 60 


1 3 


3 6 


13 


— 


1 2 




4 4 


~ 


6 


7 5 


P 5 





Table 45. Observed minus computed values of secular change in north component (X) of magnetic field intensity 

for 1942.5 expressed in units of 10-6 CGS per year 



Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


1 

L 


40 


50 




60 


70 


80 


90 


3 O 


15 3 


1 8 


80 


_ 


8 9 


„ 


2 2 




2 6 


7 


6 3 


15 


60 


142 


72 


7 6 


- 


2 4 




4 9 




5 


4 


1 5 


3 


9 


90 


10 1 





- 


3 3 




2 9 




10 9 


6 2 


12 


2 


120 


4 2 


7 4 


4 4 




5 7 


- 


3 4 




2 5 


5 4 


4 4 


1 o 


15 


6 6 


13 


5 9 


- 


4 1 


- 


5 5 


- 


9 


1 2 


2 


19 


IPO 


- 14 4 


- 10 8 


2 9 


- 


2 2 


- 


4 5 


- 


3 9 


1 2 


3 2 


2 


2 10 


- 14 4 


- 10 3 


30 




2 5 


- 


1 


- 


2 9 


2 5 


10 


3 1 


2 4 


70 


6 4 


5 5 




1 9 


- 


40 


- 


5 1 


1 


3 2 


1 5 


2 70 


3 1 


2 5 


4 


- 


4 2 


- 


6 6 


- 


2 7 


1 4 


3 4 


9 2 


3 


8 2 


6 1 


7 6 


- 


1 6 


- 


2 8 


- 


4 6 


7 6 


4 1 


14 


3 3 


3 6 


19 


2 1 




6 




5 2 


- 


6 


5 


9 


2 


3 60 


97 


3 


4 9 


- 


6 1 




6 




7 9 


2 9 


19 


1 9 





























Geographic 
east 








Ge 


ographi 


c colatitude 


in 


degrees 






longitude 
in degrees 


100 


110 


120 


130 




140 


150 


160 


170 




3 


2 6 


6 8 


7 3 




9 7 


_ 


1 5 


_ 


1" 8 


7 


4 8 




60 


4 8 


7 4 


2 1 


- 


36 


- 


R 




6 4 


18 8 


- 12 4 




90 


3 6 


6 1 


5 9 


- 


6 


- 


1 




25 3 


39 2 


- 10 9 




120 


9 


3 3 


19 9 


- 


10 3 


- 


17 9 




5 7 


32 7 


- 17 2 




15 


4 3 


46 


3 3 




4 3 


- 


5 9 


- 


10 


9 5 


6 6 




18 


2 5 


2 2 


1 6 




1 8 


- 


8 8 


- 


9 3 


8 


R 2 




210 


3 8 


4 6 


2 4 




3 5 


- 


6 2 


- 


13 4 


6 1 


19 6 




24 


9 


3 6 


3 8 




4 5 




6 9 


- 


6 7 


- 13 7 


29 




2 70 


6 3 


14 


2 1 


- 


3 1 


- 


6 5 


- 


15 6 


8 8 


37 8 




3 


3 3 


7 


8 8 


- 


1 1 




1 


- 


10 


5 1 


42 




330 


17 


1 6 


4 7 


- 


6 




5 8 




2 


3 3 


36 3 




3 60 


8 7 


1 1 


3 7 




2 4 


— 


1 3 


~ 


2 9 


4 


16 7 





44 



Table 46. Observed minus computed values of secular change in east component (Y) of magnetic field intensity 

for 1912.5 expressed in units of 10 _ 6 CGS per year 



Geographic 
east 










Geographic colatitude 


in 


degrees 








longitude 


10 




20 


30 




40 




50 




60 


70 


80 


90 


in degrees 




























30 


14 


_ 


37 


40 




1 4 




6 


_ 


2 5 


56 


2 6 


10 


60 


18 


- 


2 4 


3 


- 


1 




8 




8 


10 


2 9 


2 5 


90 


2 2 


- 


7 


30 


- 


5 1 


- 


2 5 




3 


4 9 


4 4 


3 4 


120 


4 4 




2 6 


2 2 




1 8 




5 4 




36 


2 1 


6 


3 2 


150 


1 9 




46 


4 5 


- 


56 


- 


6 1 


_ 


3 7 


2 


2 2 


2 4 


1 80 


3 3 


- 


3 8 


3 3 




1 3 




3 3 




50 


2 6 


6 


2 1 


210 


2 4 




10 


2 1 


- 


3 4 


- 


5 9 


_ 


3 9 


3 


8 


2 4 


24 


3 4 




5 6 


2 4 




9 




8 




4 


3 6 


50 


1 


2 70 


2 4 


- 


9 


5 9 


- 


40 




1 


- 


3 5 


67 


2 8 


2 4 


3 


21 


- 


3 8 


14 




41 




50 




7 





1 


11 


3 30 


28 


- 


1 3 


13 


- 


2 6 


- 


1 4 




1 1 


2 5 


6 4 


20 


3 60 


2 3 


— 


2 2 


3 6 




20 


- 


2 4 


- 


3 2 


2 9 


6 8 


2 2 




Geographic 
east 










Geographic colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


3 5 




1 9 


7 8 


_ 


4 2 


- 


36 




1 1 


2 8 


9 5 




60 


10 


- 


12 3 


5 9 




6 1 




62 




7 7 


2 5 


- 15 4 




90 


3 2 


- 


1 5 


1 




5 2 




6 


- 


2 8 


2 


76 




12 


2 2 


- 


5 


2 




6 


- 


100 


- 


3 2 


76 


66 




15 


1 2 




30 


2 4 




2 1 


- 


2 1 


- 


2 4 


6 6 


15 4 




1R0 


3 6 


- 


1 1 


5 


- 


6 




5 6 


- 


4 4 


2 8 


13 8 




2 10 


2 1 




2 


2 5 




2 9 




1 3 


- 


41 


7 2 


40 




2 4 


7 8 


- 


3 5 


1 4 




1 6 




3 


- 


5 2 


- 10 1 


34 




2 7 


2 4 


- 


7 


3 3 




4 




5 1 




2 6 


13 


20 




3 


7 




9 


4 1 


- 


5 9 


- 


4 2 




2 5 


1 9 


74 




3 3 


60 




3 6 


12 




8 




1 6 




60 


5 7 


37 




3 60 


3 5 


- 


9 5 


5 5 




10 3 


— 


2 2 




1 3 


4 2 


96 





Table 47. Observed minus computed values of secular change in east component (Y) of magnetic field intensity 

for 1922.5 expressed in units of 10-6 CGS per year 



Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


5 2 


4 


6 5 




6 2 




50 







69 


3 2 


2 5 


60 


2 9 


10 


13 


_ 


4 5 


- 


39 


- 


17 


4 3 


6 1 


4 2 


90 


10 


30 


4 3 




3 5 




7 




10 


4 3 


4 1 


5 3 


120 


17 


3 5 


20 


_ 


2 




3 5 




2 7 


1 9 


10 


1 4 


150 


1 


3 7 


5 




9 


- 


1 4 


- 


2 9 


3 1 


10 


1 1 


180 


6 7 


2 4 


2 7 




1 3 




4 1 




5 9 


40 


2 2 


16 


2 10 


6 2 


1 9 


19 


_ 


3 1 


- 


4 8 


- 


46 


17 


13 


1 8 


24 


50 


3 9 


4 2 




3 4 




4 7 




5 9 


3 4 


3 2 


8 


2 7 





14 


2 1 


_ 


6 9 


- 


4 7 


- 


60 


4 7 


4 9 


5 4 


3 


37 


3 9 


20 




9 1 




15 2 




1 


2 4 


16 


6 


33 


37 


14 


20 


- 


3 1 


- 


2 1 




4 


20 


2 7 


1 


3 60 


5 2 


18 


6 3 




3 3 


- 


1 8 


- 


2 8 


4 


5 3 


9 4 




Geographic 
east 








Get 


)graphi 


; colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


1 1 


5 8 


12 5 




71 




3 3 




39 


2 


8 5 




60 


8 


11 


37 


_ 


2 6 


— 


36 


- 


6 


6 1 


67 




90 


3 


1 9 


8 5 




12 5 




96 




1 7 


39 


7 9 




120 


2 


6 2 


17 


_ 


6 1 


- 


8 3 


- 


7 9 


8 


6 8 




15 


2 8 


8 2 


6 5 




1 3 




72 




2 5 


10 


5 1 




180 


3 


4 


1 7 




2 5 




2 6 




2 8 


1 3 


86 




2 10 


5 8 


6 3 


6 6 




2 3 


- 


10 


- 


6 9 


83 


2 5 




24 


4 2 


1 


56 




60 


- 


1 


- 


3 6 


7 4 


8 




2 70 


1 5 


27 


2 2 




7 5 




70 




37 


10 


6 8 




3 


6 5 


2 6 


2 


- 


2 8 


- 


8 9 


- 


2 1 


5 4 


81 




3 3 


60 


4 3 


5 2 




6 1 




9 2 




7 5 


2 1 


2 5 




3 60 


1 6 


6 6 


5 7 




4 3 


- 


1 4 




49 


9 5 


- 16 5 





45 



Table 48. Observed minus computed values of secular change in east component (Y) of magnetic field intensity 

for 1932.5 expressed in units of 10-6 CGS per year 



Geographic 
east 










Geographic colatitude 


in degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


_ 


3 2 


4 2 


8 3 


_ 


1 2 




8 5 


4 


17 


7 


4 


60 


- 


2 5 


1 6 


2 4 




1 4 




1 9 


1 3 


37 


1 4 


3 8 


90 


- 


3 2 


1 


6 3 




5 4 




4 


13 


3 2 


5 


4 4 


120 


- 


20 


3 9 


11 


- 


37 




1 6 


40 


3 7 


6 6 


3 3 


15 


- 


4 2 


18 


10 




10 




3 


2 


3 


33 


13 


180 


- 


3 


2 2 


10 




1 3 




2 1 


2 8 


2 9 


2 8 


1 8 


2 10 




2 4 


6 


2 


- 


3 


- 


8 





6 


1 3 


1 


24 




3 3 


3 4 


5 


- 


3 5 




2 7 


86 


5 4 


2 6 


3 2 


2 70 




3 2 


3 3 


8 2 


- 


10 2 


- 


1 3 





137 


5 


- 10 4 


3 




2 8 


2 4 


1 




2 6 




5 3 


5 8 


7 


6 9 


2 2 


3 3 


- 


2 5 


1 2 


1 


- 


2 7 


- 


30 


1 8 


3 3 


1 7 


10 


3 60 


- 


6 3 


9 


10 




40 




3 1 


13 


2 1 


3 6 


1 




Geographic 
east 










Geographic colatitude 


in degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


_ 


1 9 


2 


5 9 




1 5 


_ 


3 


9 8 


30 


- 15 1 




60 




3 8 


6 


8 3 


- 


41 




8 3 


9 4 


3 5 


- 119 




90 




1 2 


2 1 


2 




1 




8 


60 


8 2 


1 2 




12 


_ 


7 5 


3 3 


5 3 




8 5 


- 


2 1 


- 100 


3 4 


104 




15 


- 


4 6 


2 5 


5 5 




5 5 


- 


116 


8 9 


3 


89 




18 


- 


4 6 


4 3 


16 




4 2 




7 5 


61 


5 6 


87 




2 10 


- 


1 7 


2 


2 6 




2 9 




2 2 


40 


- 117 


13 




24 


- 


3 4 


2 9 


3 5 


- 


1 2 


- 


6 7 


36 


4 


4 2 




2 70 


- 


4 8 


4 8 


8 2 




36 




7 


4 8 


118 


18 7 




3 




4 9 


7 


4 6 


- 


5 9 


- 


6 2 


1 7 


6 3 


169 




3 3 


_ 


41 


18 


3 5 




6 5 




7 3 


6 7 


3 1 


3 2 




3 60 


- 


1 2 


2 9 


19 


- 


2 5 




2 2 


46 


99 


- 215 





Table 49. Observed minus computed values of secular change in east component (Y) of magnetic field intensity 

for 1942.5 expressed ir. units of 10-6 CGS per year 



Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


_ 


80 


2 2 


7 3 


_ 


2 2 




20 


_ 


1 5 


_ 


6 


_ 


2 1 


40 


60 


_ 


4 


5 5 


10 


- 


1 


- 


5 


_ 


2 


- 


39 




2 2 


6 


90 


- 


1 9 


6 5 


4 9 


- 


1 


- 


37 


- 


Z 4 


- 


2 6 


- 


3 


1 o 


12 


- 


2 3 


2 2 


2 


~ 


57 


- 


3 8 




1 8 




2 2 




1 4 


49 


15 


- 


3 1 


4 6 


7 


- 


1 3 


- 


2 2 







- 


8 


- 


2 9 


31 


18 




4 


6 


9 


- 


1 4 


- 


2 2 




10 


- 


1 


- 


10 


17 


210 




2 7 


7 


2 9 


- 


1 1 


- 


3 2 


- 


3 6 


- 


2 2 


- 


6 


12 


2 4 


_ 


1 


2 


17 


- 


1 




9 




1 3 




1 


- 


3 5 


27 


2 70 




3 3 


50 


70 


- 


82 


- 


6 


- 


1 


- 


1 2 


- 


5 


34 


3 




3 4 


17 


1 2 




10 




1 6 




17 


- 


6 1 


- 


1 9 


9 


3 3 




2 9 


6 


5 2 




17 


- 


5 


- 


47 


- 


4 


- 


2 1 





3 60 


- 


4 2 


3 9 


2 8 


- 


6 


- 


3 


- 


1 3 




4 


- 


5 


13 




Geographic 
east 










Geographic 


colatitude 


in 


degrees 












longitude 
in degrees 




100 


110 


120 


130 


140 


150 


160 


170 




30 


m 


3 8 


2 5 


7 8 




4 


_ 


30 


_ 


1 


_ 


41 


- 


13 5 




60 


_ 


2 3 


7 


11 


- 


6 4 


- 


2 4 




4 8 


- 


1 6 


- 


10 2 




90 


_ 


2 9 


2 6 


8 




5 1 




4 3 




1 1 


- 


1 1 




10 




120 


_ 


6 6 


7 


9 1 


- 


2 2 


- 


117 


- 


6 4 


- 


1 5 




20 1 




15 


- 


3 1 


1 9 


4 4 




4 9 


- 


2 6 


- 


12 


- 


130 




3 6 




1 RO 


- 


1 4 


8 


16 


- 


2 2 




6 




4 8 




5 2 




11 3 




2 10 


_ 


1 5 


1 3 


1 8 




1 2 


- 


1 6 


- 


4 8 




9 




2 9 




2 4 




1 


5 


12 




6 


- 


4 


- 


7 3 


- 


46 


- 


3 8 




2 70 


- 


3 6 


2 2 


3 9 


- 


6 




1 4 




1 4 




3 2 


- 


13 5 




3 




1 2 


2 1 


15 


- 


4 4 


- 


2 7 




3 3 




2 4 


- 


22 3 




3 3 


_ 


1 4 


10 


2 2 




1 3 


- 


7 




5 4 




118 


- 


146 




3 60 


- 


3 4 


1 


2 8 


~ 


4 5 


- 


60 


— 


4 




10 2 


•• 


6 8 





Table 50. Computed values of secular change in north component (X) of magnetic field intensity for 1932.5 
at height 100 km expressed in units of 10-6 CGS per year 



Geographic 
east 














Geographic colatitude in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


_ 


37 5 


_ 


396 


_ 


321 


_ 


157 




4 3 




20 2 




23 6 


106 


- 16 


60 


- 


521 


- 


51 3 


- 


42 4 


- 


26 6 


- 


6 3 




139 




27 4 


26 6 


84 


90 


- 


51 S 


- 


47 1 


- 


34 9 


- 


16 5 




5 3 




26 7 




4 2 


44 6 


30 2 


12 


- 


40 2 


- 


34 8 


- 


24 1 


- 


100 




3 3 




11 4 




12 4 


7 3 





150 


- 


22 1 


- 


20 2 


- 


15 4 


- 


77 




1 8 




97 




111 


3 5 


9 7 


18 


- 


1 9 


- 


5 2 


- 


5 4 


- 


3 2 




6 




4 1 




4 3 


15 


- 13 2 


210 




17 1 




70 




1 


- 


40 


- 


7 2 


- 


107 


- 


15 4 


- 215 


- 28 9 


240 




33 1 




18 8 




47 


- 


8 8 


- 


21 3 


- 


31 4 


- 


36 9 


- 37 5 


- 36 2 


270 




42 3 




29 8 




114 


- 


130 


- 


39 2 


- 


580 


_ 


60 8 


- 46 6 


- 25 9 


3 




384 




31 4 




17 7 


- 


2 9 


- 


25 9 


- 


42 1 


_ 


4 3 6 


- 30 7 


- 13 8 


3 30 




187 




16 4 




16 6 




19 4 




217 




19 2 




9 1 


70 


- 25 3 


3 60 


- 


106 


- 


12 8 


- 


6 7 




7 3 




23 5 




32 3 




26 9 


7 1 


- 20 8 




Geographic 
east 














Geographi 


c colatitude in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


^ 


4 6 1 


_ 


66 4 


_ 


66 9 


_ 


470 


_ 


16 




118 




25 1 


22 2 




60 


- 


21 2 


- 


4 80 


- 


56 5 


- 


410 


- 


110 




14 5 




19 7 


34 




90 




16 


- 


29 5 


- 


48 9 


- 


4 8 5 


- 


33 3 


- 


184 


- 


176 


- 310 




12 


- 


5 5 


- 


6 6 


- 


4 2 


- 


2 5 


- 


7 3 


- 


217 


- 


4 2 4 


- 58 6 




15 


_ 


20 5 


- 


21 2 


- 


11 7 


- 


1 5 


- 


2 7 


- 


200 


- 


4 5 4 


- 620 




18 


- 


26 1 


- 


340 


- 


334 


- 


26 9 


- 


21 3 


- 


22 8 


- 


31 


- 39 




2 10 


_ 


37 2 


- 


44 6 


- 


47 5 


- 


42 8 


- 


301 


- 


140 


- 


2 3 


12 




2 4 


- 


38 5 


- 


46 5 


- 


55 2 


- 


54 9 


- 


38 3 


- 


8 8 




19 4 


30 8 




2 7 


_ 


147 


- 


22 3 


- 


43 2 


- 


59 3 


- 


53 8 


- 


24 3 




14 4 


412 




3 


_ 


7 7 


- 


20 8 


- 


47 8 


- 


72 


- 


75 5 


- 


515 


- 


8 9 


331 




3 3 


- 


42 9 


- 


59 3 


- 


74 2 


- 


84 2 


- 


817 


- 


601 


- 


20 8 


23 5 




3 60 


- 


4 8 3 


- 


6 8 1 


— 


766 


— 


73 1 


— 


57 7 


- 


326 


— 


2 9 


23 1 




Table 51. 


c 


omputec 


1 values of 


sea 


liar cha 


nge 


in north component (X) of magnet 


c field 


intensity for 1932.5 










at height 300 km expressed in units of 10-6 CGS per year 






Geographic 
east 














Geographi 


c colatitude in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


_ 


32 7 


„ 


34 3 


_ 


27 7 


_ 


137 




31 




16 3 




18 9 


77 


- 148 


60 


- 


4 6 


- 


45 1 


- 


37 2 


- 


23 3 


- 


57 




11 5 




226 


21 5 


60 


90 


- 


46 


- 


41 6 


- 


30 8 


- 


148 




41 




22 4 




352 


36 9 


24 5 


120 


- 


356 


- 


307 


- 


21 3 


- 


9 1 




2 4 




9 6 




107 


6 6 


2 


15 


- 


195 


- 


17 7 


- 


134 


- 


67 




1 3 




77 




86 


2 3 


86 


180 


- 


1 4 


- 


4 3 


- 


4 6 


- 


27 




3 




30 




2 7 


2 5 


- 12 5 


2 10 




15 5 




67 




3 


- 


3 6 


- 


67 


- 


101 


- 


14 4 


- 19 8 


- 2'6 4 


24 




29 6 




170 




4 2 


- 


79 


- 


191 


- 


28 1 


- 


33 1 


- 339 


- 33 2 


2 70 




37 5 




26 2 




97 


- 


116 


- 


340 


- 


500 


- 


52 6 


- 413 


- 24 8 


30 




341 




27 7 




15 5 


- 


2 2 


- 


21 8 


- 


35 6 


- 


37 5 


- 27 5 


- 146 


330 




169 




150 




150 




17 




18 3 




15 7 




6 9 


70 


- 230 


3 60 


- 


8 8 


- 


103 


- 


50 




67 




19 9 




26 9 




21 9 


4 8 


- 19 2 




Geographic 
east 














Geographi 


c colatitudt 


! in 


degree; 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


- 


40 1 


_ 


570 


- 


576 


_ 


411 


_ 


153 




80 




197 


181 




60 


- 


188 


- 


40 9 


- 


480 


- 


35 5 


- 


110 




100 




147 


2 1 




90 




5 


- 


254 


- 


417 


- 


417 


- 


296 


- 


17 7 


- 


167 


- 270 




12 


- 


4 8 


- 


6 3 


- 


5 2 


- 


45 


- 


91 


- 


21 2 


- 


37 9 


- 50 3 




15 


- 


175 


- 


183 


- 


112 


- 


37 


- 


5 4 


_ 


19 9 


- 


404 


- 53 2 




180 


- 


234 


- 


302 


- 


30 


- 


24 9 


- 


20 5 


- 


216 


- 


280 


- 33 9 




210 


- 


33 6 


- 


397 


- 


420 


- 


379 


- 


271 


- 


13 5 


- 


3 5 


2 2 




24 


- 


35 3 


- 


417 


- 


483 


- 


473 


- 


330 


- 


84 




149 


24 5 




2 70 


- 


15 9 


- 


22 


- 


385 


- 


510 


- 


45 8 


- 


212 




10 8 


334 




3 


- 


103 


- 


21 3 


- 


43 4 


- 


62 8 


- 


65 1 


- 


44 6 


- 


8 9 


268 




3 3 


- 


387 


- 


53 2 


- 


66 2 


- 


74 4 


- 


71 6 


- 


52 5 


- 


18 8 


19 1 




3 60 


m 


4 30 


— 


60 2 


" 


677 


- 


646 


■• 


511 


- 


29 2 


- 


3 6 


189 





47 



Table 52. 



Computed values of secular change in north component (X) of magnetic field intensity for 1932.5 
at height 500 km expressed in units of 10-6 CGS per year 



Geographic 
east 














Geographic colatitude 


in 


degrees 










longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


_ 


28 7 




29 8 


- 


24 


_ 


12 1 




2 1 




131 




15 1 


5 4 


- 136 


60 


_ 


4 6 


_ 


39 8 


- 


32 7 


_ 


20 5 


_ 


5 2 




9 5 




187 


17 5 


4 2 


90 


- 


4 8 


_ 


369 


- 


27 3 


- 


13 3 




31 




18 8 




29 5 


30 7 


200 


12 


- 


31 7 


_ 


27 3 


- 


19 


- 


8 3 




1 7 




81 




9 2 


5 8 


4 


15 


- 


173 


_ 


156 


- 


118 


- 


5 9 




8 




60 




6 7 


1 3 


7 8 


180 


- 


11 


. 


36 


- 


3 9 


- 


2 4 









2 




1 5 


32 


- 118 


2 10 




141 




6 3 




5 


_ 


3 3 


_ 


6 3 


- 


9 5 


- 


13 4 


- 183 


- 241 


2 4 




26 5 




15 4 




3 8 


- 


71 


_ 


17 2 


- 


25 2 


- 


29 7 


- 30 7 


- 30 5 


2 70 




33 4 




23 2 




8 4 


- 


10 3 


_ 


29 6 


- 


4 3 4 


- 


45 9 


- 36 9 


- 236 


30 




30 3 




24 5 




137 


- 


17 


_ 


18 5 


- 


30 4 


- 


32 4 


- 24 9 


- 14 8 


3 3 




15 3 




137 




13 6 




149 




15 6 




12 9 




5 1 


7 


- 210 


3 60 


- 


7 4 


- 


8 4 


— 


3 7 




62 




17 




22 5 




17 9 


30 


- 17 7 




Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


100 


110 




120 




130 


140 


150 


160 


170 




3 


_ 


35 


_ 


49 3 


- 


49 8 


— 


36 1 


_ 


14 5 




5 2 




15 5 


149 




60 


- 


16 6 


_ 


35 2 


- 


412 


- 


30 9 


- 


107 




67 




10 9 


1 1 




90 


- 


3 


- 


22 1 


- 


35 7 


- 


36 1 


- 


26 5 


- 


16 8 


- 


15 8 


- 236 




12 


- 


4 2 


_ 


61 


- 


5 8 


- 


5 9 


- 


103 


- 


20 4 


- 


339 


- 43 3 




150 


- 


15 1 


_ 


16 


- 


10 7 


_ 


5 £ 


- 


72 


- 


19 4 


- 


36 1 


- 45 8 




180 


- 


21 1 


- 


26 9 


- 


270 


_ 


230 


- 


19 6 


- 


20 4 


-. 


25 3 


- 29 6 




2 10 


- 


30 4 


_ 


35 6 


- 


37 4 


- 


33 7 


- 


24 4 


- 


12 9 


- 


4 3 


2 9 




2 4 


- 


32 3 


_ 


37 5 


,. 


4 2 5 


- 


410 


- 


28 7 


- 


8 1 




115 


19 7 




2 70 


- 


16 5 


_ 


21 4 


- 


34 5 


- 


4 4 2 


- 


39 4 


- 


187 




81 


27 2 




3 


- 


119 


- 


21 3 


- 


39 5 


- 


551 


- 


56 5 


- 


390 


- 


86 


21 8 




3 3 


_ 


34 9 


_ 


47 9 


- 


59 3 


- 


66 


- 


630 


- 


46 1 


- 


170 


15 6 




3 60 


- 


38 3 


- 


53 5 


*- 


601 


- 


57 3 


- 


45^ 


- 


26 3 


- 


40 


15 6 




Table 53 


. C 


ompute 


d values of 


seci 


jlar change 


in north component (X) of magnet 


ic field 


intensity for 1932.5 










at heig 


ht 1000 km 


expressed i 


n units of 10-6 CGS per year 






Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


m 


21 1 


m 


21 5 


M 


17 3 


„. 


91 




5 




76 




8 5 


1 7 


- 113 


60 


- 


305 


- 


29 6 


- 


24 3 


- 


15 3 


- 


4 5 




5 6 




11 6 


10 4 


1 3 


90 


- 


30 9 


- 


27 8 


- 


207 


- 


105 




1 2 




121 




19 3 


197 


121 


1 20 


- 


240 


- 


206 


- 


14 5 


~ 


6 8 




4 




51 




6 3 


4 1 


3 


150 


- 


13 


- 


11 6 


- 


86 


- 


4 5 


- 







3 2 




3 4 


1 


6 1 


180 


- 


6 


_ 


2 4 


„ 


2 7 


- 


1 8 


- 


4 




4 


- 


4 


41 


- 10 2 


2 10 




110 




5 3 




7 


- 


2 6 


- 


5 3 


- 


81 


- 


113 


- 15 1 


- 19 5 


24 




20 3 




11 9 




30 


- 


5 6 


- 


13 4 


- 


19 5 


- 


23 1 


- 243 


- 247 


2 70 




25 3 




17 3 




60 


- 


7 7 


- 


21 5 


- 


31 1 


- 


33 3 


- 28 3 


- 20 5 


30 




230 




183 




103 


- 


8 


- 


12 6 


- 


211 


- 


23 3 


- 196 


- 14 4 


3 30 




12 




110 




107 




10 9 




106 




80 




2 1 


67 


-17 1 


3 60 


- 


4 8 


- 


5 1 


- 


17 




47 




115 




14 5 




107 


1 


- 14 6 




Geographic 
east 














Geographic 


: colatitude 


In 


degrees 










longitude 




100 




110 




120 




130 




140 




150 




160 


170 




in degrees 


































30 


_ 


25 5 


_ 


35 1 


_ 


35 6 


_ 


267 


. 


12 5 




8 




84 


91 




60 


- 


12 5 


- 


24 7 


_ 


286 


- 


22 3 


,_ 


96 




1 5 




48 


3 




90 


- 


1 4 


- 


15 9 


- 


25 1 


- 


25 9 


- 


20 3 


- 


144 


- 


134 


- 17 2 




120 


- 


3 2 


- 


5 5 


- 


6 3 


- 


76 


- 


111 


- 


17 8 


- 


25 8 


- 306 




15 


- 


109 


_ 


11 9 


- 


95 


- 


71 


- 


9 4 


- 


174 


- 


27 4 


- 324 




1 80 


- 


166 


- 


20 6 


- 


21 1 


- 


190 


- 


16 9 


- 


173 


- 


19 8 


- 215 




210 


- 


240 


- 


27 5 


- 


28 5 


- 


256 


- 


19 2 


-» 


11 3 


- 


5 3 


3 5 




24 


- 


26 1 


- 


29 1 


- 


31 5 


- 


29 6 


- 


20 8 


- 


71 




57 


11 5 




2 70 


- 


16 3 


- 


19 2 


- 


26 7 


- 


31 8 


- 


27 8 


- 


140 




36 


166 




30 


- 


13 5 


- 


200 


- 


31 5 


- 


40 8 


- 


407 


- 


28 4 


- 


77 


132 




3 30 


- 


27 6 


- 


374 


- 


45 5 


- 


49 7 


- 


46 7 


- 


341 


- 


134 


9 4 




3 60 


- 


29 4 


- 


403 


** 


45 2 


- 


430 


— 


34 3 


- 


20 5 


~ 


44 


9 7 





48 



Table 54. Computed values of secular change in north component (X) of magnetic field intensity for 1932.5 
at height 5000 km expressed in units of 10-6 CGS per year 



Geographic 
east 












Geographi 


c colatitude 


in degrees 












longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3Q 


_ 


3 3 


_ 


33 - 


2 8 


— 


21 


- 


13 


9 


„ 


11 


_ 


19 


32 


60 


- 


5 3 


— 


5 2- 


45 


— 


3 3 


_ 


21 


10 


.. 


5 


— 


7 


16 


90 


- 


57 


— 


5 2- 


43 


— 


2 9 


_ 


14 


2 




4 




4 


3 


120 


- 


45 


- 


40 - 


32 


- 


21 


«. 


11 


4 


_ 


2 


- 


3 


8 


ISO 


- 


2 5 


- 


28 - 


1 8 


- 


13 


_ 


9 


8 


_ 


9 


- 


13 


19 


1 80 


- 


1 


— 


3 - 


5 


- 


7 


_ 


9 


12 


_ 


17 


- 


25 


3 3 


210 




20 




11 


1 


- 


8 


— 


17 


2 5 


_ 


34 


- 


42 


50 


240 




37 




2 2 


5 


- 


12 


- 


28 


41 


_ 


51 


- 


5 8 


62 


270 




45 




29 


9 


- 


1 2 


_ 


32 


48 


_ 


58 


- 


61 


6 1 


30 




42 




3 2 


18 




1 


_ 


16 


31 


_ 


42 


- 


49 


5 4 


330 




2 5 




23 


19 




14 




7 


2 


— 


1 5 


- 


3 1 


49 


360 


- 


2 


- 


2 







3 




5 


2 


- 


7 


- 


23 


42 




Geographic 
east 












Geographi 


c colatitude 


in degrees 












longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


_ 


46 


_ 


54 - 


5 5 


„ 


48 


— 


35 


21 


wm 


8 




1 




60 


- 


27 


- 


37 - 


41 


- 


37 


— 


2 8 


19 


- 


11 


- 


7 




90 


- 


15 


— 


28 - 


38 


- 


41 


_ 


39 


3 5 


_ 


30 


- 


2 4 




120 


- 


1 5 


- 


2 2- 


29 


- 


36 


— 


41 


45 


- 


45 


- 


39 




150 


- 


26 


— 


31 - 


35 


— 


39 


_ 


44 


48 


_ 


49 


- 


42 




1 80 


- 


41 


- 


47 - 


50 


- 


50 


- 


48 


45 


- 


40 


- 


32 


' 


21 


- 


56 


- 


5 9- 


5 8 


- 


5 4 


_ 


45 


3 4 


- 


2 4 


- 


1 5 




240 


- 


64 


- 


64 - 


61 


- 


53 


— 


41 


2 5 


- 


11 


- 


1 




270 


- 


6 1 


- 


6 1 - 


6 1 


- 


57 


_ 


48 


31 


- 


13 




4 




30 


- 


60 


— 


6 8- 


74 


- 


7 5 


_ 


68 


50 


- 


2 5 




1 




330 


- 


66 


- 


81 - 


90 


- 


90 


_ 


80 


5 9 


- 


3 1 


- 







3 60 


- 


61 


— 


7 5 - 


81 


- 


77 


- 


64 


44 


- 


21 




1 




Table 5E 


. Compute 


>d v 


ilues of secular change in north component (X) of magnetic fielc 


intensity for 1942.5 










at height 100 km 


exp 


ressed in units of 10-6 CGS per year 








Geographic 
east 












Geographic colatitude 


in degrees 












longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


_ 


29 9 


_ 


25 5 - 


14 5 




1 1 




17 9 


30 9 




347 




24 9 


2 2 


60 


- 


40 1 


- 


35 3 - 


22 7 


- 


5 9 




12 5 


30 9 




4 6 




51 1 


39 3 


90 


- 


37 1 


- 


27 8 - 


8 5 




130 




29 7 


4 1 




46 6 




4 9 5 


44 3 


12 


- 


24 3 


- 


15 9 - 


3 




149 




2 2-5 


212 




16 1 




13 4 


14 3 


150 


- 


6 7 


- 


3 2 


3 1 




R 5 




9 8 


7 4 




47 




3 6 


3 5 


1 BO 




9 8 




a 4 


86 




R 5 




5 9 


8 


- 


4 9 


_ 


9 6 


- 13 5 


2 10 




21 1 




13 8 


7 9 




3 5 


- 


10 


6 8 


- 


13 9 


_ 


21 


- 27 4 


24 




26 6 




17 8 


130 




10 3 




5 1 


50 


- 


180 


_ 


29 5 


- 37 3 


2 70 




26 7 




209 


19 




16 




6 2 


9 4 


- 


23 3 


_ 


28 5 


- 26 6 


30 




21 1 




21 3 


25 2 




27 8 




24 1 


14 7 




5 1 


_ 


5 


5 3 


3 30 




R 5 




157 


28 3 




40 5 




44 4 


36 9 




215 




4 6 


- 106 


3 60 


- 


10 5 


- 


2 5 


115 




26 4 




35 4 


34 5 




24 




7 2 


- 12 2 




Geographic 
east 












Geographi 


c colatitude 


in degrees 












longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


-B 


26 2 


— 


47 7 - 


51 


_ 


340 


_ 


60 


16 8 




21 8 




81 




60 




111 


- 


22 3 - 


43 9 


- 


42 7 


- 


22 9 


19 




2 2 


- 


14 5 




90 




25 9 


_ 


30 - 


312 


- 


45 6 


- 


42 9 


- 33 


- 


30 3 


- 


407 




12 




14 8 




10 5 


1 4 


- 


8 8 


- 


17 9 


- 271 


- 


38 9 


- 


51 3 




150 




1 9 


- 


15 - 


5 2 


- 


7 3 


- 


9 3 


- 15 1 


- 


26 5 


- 


386 




180 


- 


17 5 


- 


215 - 


230 


- 


196 


- 


11 8 


4 2 


- 


2 4 


- 


79 




210 


_ 


33 3 


- 


38 - 


38 7 


- 


31 1 


- 


138 


8 3 




25 4 




27 6 




24 


_ 


43 5 


- 


501 - 


540 


- 


4 7 4 


- 


24 6 


97 




40 6 




51 9 




2 7 


- 


27 1 


- 


37 1 - 


526 


- 


59 1 


- 


4 3 8 


81 




31 3 




54 7 




3 


- 


17 


- 


39 6 - 


6 6 3 


- 


81 6 


- 


72 3 


- 3R 4 




5 6 




40 7 




3 30 


- 


26 3 


- 


45 3 - 


65 2 


- 


770 


- 


70 6 


- 44 1 


- 


6 6 




25 7 




3 60 


- 


31 6 


- 


47 9 - 


56 4 


— 


527 


•■ 


36 5 


- 130 




7 8 




18 





49 



Table 56 


. Computed values of 


secular change 


in north component (5 


f) of magnet 


lc field intensity fo 


r 1942.5 








at height 


300 km expressed in units of 10-6 


CGS pei 


' ye 


ar 






Geographic 
east 












Geographic colatitude 


in 


degrees 










longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


- 25 6 


_ 


21 6 


_ 


12 1 




1 3 




15 6 




26 5 




29 4 


21 


1 7 


60 


- 347 


- 


30 4 


- 


19 4 


- 


47 




113 




27 2 




39 a 


43 5 


• 33 


90 


- 32 1 


- 


24 


- 


7 5 




10 9 




25 6 




35 1 




4 9 


43 


37 7 


12 


- 20 9 


- 


13 4 


- 


3 




12 6 




19 3 




188 




150 


12 8 


13 1 


15 


5 6 


- 


2 3 




2 9 




7 4 




a 5 




6 6 




4 3 


3 2 


2 8 


180 


8 a 




77 




7 7 




7 3 




50 




6 


- 


4 4 


8 7 


- 12 2 


2 10 


189 




12 7 




7 5 




3 4 


- 


9 


- 


6 4 


- 


12 7 


- 19 1 


- 24 8 


2 4 


24 




16 5 




119 




R 9 




3 8 


- 


5 2 


- 


16 4 


- 26 3 


- 33 3 


2 7 


24 5 




19 4 




17 3 




14 




5 2 


- 


80 


- 


19 8 


- 24 8 


- 24 3 


3 


19 7 




200 




2 3 




24 7 




21 2 




13 




4 6 


10 


6 2 


3 3 


8 5 




149 




25 5 




35 4 




38 5 




32 




1 R 9 


4 1 


9 8 


3 60 


8 4 


- 


1 3 




10 6 




23 2 




30 8 




29 9 




20 9 


6 2 


- 1 8 


































Geographic 
east 












Geographic colatitude 


in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


- 22 


_ 


40 


_ 


43 1 


_ 


29 4 


_ 


6 7 




119 




16 2 


5 3 




60 


9 2 


- 


18 6 


- 


36 8 


- 


36 4 


_ 


20 8 


- 


41 


- 


8 


- 14 1 




90 


217 


- 


2 a 


- 


26 6 


- 


39 1 


- 


37 8 


- 


30 4 


- 


28 4 


- 36 4 




120 


12 8 




R 5 




3 


- 


a 9 


_ 


17 3 


- 


25 7 


- 


35 6 


- 45 1 




15 


1 3 


- 


1 7 


- 


4 9 


- 


72 


- 


9 5 


- 


150 


- 


24 5 


- 33 9 




1 BO 


- 15 8 


- 


19 1 


- 


20 4 


- 


17 5 


_ 


110 


- 


4 8 


- 


3 2 


7 4 




2 10 


- 29 9 


- 


33 7 


- 


33 8 


- 


27 


- 


12 2 




6 5 




20 8 


23 




2 4 


- 38 9 


- 


4 4 2 


- 


46 9 


- 


4O4 


_ 


20 R 




79 




33 7 


4 3 4 




2 70 


- 25 6 


- 


34 1 


- 


46 4 


- 


50 8 


_ 


37 5 


- 


7 6 




25 3 


45 5 




3 


- 17 1 


- 


36 3 


- 


584 


- 


70 5 


_ 


62 3 


- 


33 8 




3 3 


33 5 




3 3 


- 24 2 


- 


4 10 


- 


57 9 


- 


67 5 


_ 


616 


- 


38 9 


- 


70 


20 8 




3 60 


- 28 


- 


42 1 


- 


49 3 


- 


46 3 


- 


32 5 


- 


12 7 




50 


14 1 





Table 57. Computed values of secular change in north component (X) of magnetic field intensity for 1942.5 
at height 500 km expressed in units of 10-6 CGS per year 



Geographic 
east 










Ge 


ographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


- 22 1 


_ 


18 5 


- 101 




1 4 




13 6 




22 8 


25 1 


177 


1 3 


6 


- 30 3 


- 


26 3 


- 16 7 


- 


3 7 




103 




24 


34 5 


372 


27 9 


Q 


- ?. 8 


- 


20 8 


6 7 




9 2 




22 2 




30 8 


359 


37 4 


32 4 


12 


- 18 1 


- 


114 


2 




10 7 




16 7 




16 7 


139 


121 


119 


15 


4 7 


- 


17 


2 8 




6 5 




7 4 




5 9 


3 9 


2 8 


2 2 


1 8 


7 9 




7 1 


6 9 




6 4 




4 2 




3 


40 


7 8 


- Ill 


2 10 
2 4 


16 9 




117 


71 




3 2 


- 


9 


_ 


5 9 


- 11 6 


- 17 3 


- 22 5 


21 7 




15 3 


10 9 




77 




2 8 


_ 


5 2 


- 149 


- 23 6 


- 29 9 


2 7 


22 3 




18 1 


15 7 




12 3 




4 4 


- 


6 8 


- 170 


- 218 


- 22 2 


3 


18 3 




187 


21 




22 




187 




115 


40 


14 


6 8 


3 3 
3 60 


8 3 




14 1 


23 1 




312 




33 5 




27 9 


16 6 


3 5 


91 


6 8- 


- 


4 


9 8 




20 5 




26 8 




260 


1 ai 


5 3 


9 8 




Geographic 
east 










Geographi 


c colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


- 187 


_ 


33 9 


- 36 6 


_ 


25 5 


_ 


71 




81 


118 


3 2 




60 


7 7 


- 


15 7 


- 311 


- 


312 


- 


18 9 


- 


56 


2 9 


- 13 5 




90 


18 3 


- 


2 6 


- 22 8 


- 


33 8 


- 


33 4 


- 


27 9 


- 26 5 


- 32 5 




12 


110 




6 9 


5 


- 


89 


- 


16 6 


- 


24 2 


- 32 4 


- 39 7 




15 


8 


- 


1 8 


4 7 


- 


70 


- 


96 


- 


14 5 


- 22 5 


- 29 7 




18 


- 143 


- 


17 1 


- 18 1 


- 


15 6 


- 


103 


_ 


5 2 


37 


67 




2 10 


- 26 9 


- 


30 


- 29 7 


- 


23 6 


- 


10 8 




5 


17 2 


193 




24 


- 34 9 


- 


39 3 


- 40 9 


- 


34 8 


- 


17 8 




6 4 


28 1 


36 6 




2 70 


- 24 


- 


313 


- 411 


- 


4 4 


- 


32 3 


- 


71 


20 6 


38 1 




3 


- 16 8 


- 


33 3 


- 516 


- 


614 


- 


541 


- 


29 8 


1 6 


27 7 




3 30 


- 22 3 


- 


37 2 


- 516 


- 


59 4 


- 


540 


- 


34 4 


7 2 


16 9 




3 60 


- 24 8 


~ 


37 1 


- 43 4 


- 


40 8 


- 


29 1 


- 


12 3 


2 9 


110 





50 



Table 58. Computed values of secular change in north component (X) of magnetic field intensity for 1942.5 
at height 1000 km expressed in units of 10-6 CGS per year 



Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


- 15 6 


- 12 7 


6 6 




1 5 




9 9 




160 


17 2 


119 


7 


60 


- 219 


- 1R7 


- 117 


- 


2 2 




ft 




17 7 


246 


25 7 


18 9 


90 


- 20 3 


- 14 9 


5 




6 3 




15 9 




22 5 


26 4 


26 9 


22 6 


120 


- 13 1 


80 


2 




74 




119 




12 7 


114 


101 


9 4 


15 


3 4 


8 


2 3 




4 8 




5 5 




4 5 


3 1 


2 1 


1 3 


1 ft 


5 9 


5 6 


5 2 




4 5 




2 ft 


_ 




3 2 


6 2 


R 8 


210 


12 9 


9 4 


5 9 




2 6 


- 


ft 


_ 


4 9 


9 4 


- 13 8 


- 17 6 


24 


16 9 


12 4 


8 8 




5 5 




1 2 


_ 


4 8 


- 119 


- 18 2 


- 23 1 


2 7 


17 9 


14 8 


12 5 




9 1 




3 2 


_ 


4 ft 


- 12 1 


- 16 2 


- 17 9 


3 


150 


15 6 


167 




16 7 




14 




ft 6 


2 8 


2 1 


7 3 


3 3 


7 6 


12 


18 




23 1 




24 3 




20 2 


12 1 


2 3 


7 6 


3 60 


3 9 


ft 


ft 




15 2 




19 4 




1 ft 7 


130 


3 6 


7 5 




Geographic 
east 








Geographic co 


latitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


13C 


140 


150 


160 


170 




30 


- 12 7 


- 22 9 


- 25 1 


_ 


185 


_ 


7 2 




2 3 


49 







60 


50 


- 10 5 


- 210 


- 


21 9 


- 


150 


- 


7 3 


5 7 


- 11 9 




90 


12 3 


2 2 


- 16 


- 


24 1 


- 


25 


- 


22 5 


- 218 


- 24 9 




120 


7 ft 


40 


17 


- 


ft 4 


- 


14 5 


- 


20 2 


- 25 7 


- 29 4 




150 





19 


4 3 


- 


6 5 


- 


90 


- 


12 9 


- 180 


- 218 




1 ft 


- 112 


- 13 1 


- 13 7 


- 


12 


- 


8 6 


- 


5 3 


40 


5 3 




2 10 


- 20 ft 


- 22 7 


- 22 


- 


17 2 


- 


81 




2 6 


10 9 


12 8 




2 4 


- 26 8 


- 29 5 


- 29 7 


- 


24 5 


- 


12 4 




3 9 


183 


24 5 




2 70 


- 20 2 


- 25 2 


- 30 ft 


- 


31 6 


- 


23 


_ 


60 


127 


25 1 




3 


- 15 3 


- 26 8 


- 3ft 7 


- 


4 4 3 


- 


38 9 


- 


22 3 


7 


177 




3 3 


- 18 1 


- 29 2 


- 39 1 


- 


4 4 


- 


39 7 


- 


259 


70 


10 2 




3 6 


- 187 


- 27 6 


- 32 1 


- 


30 3 


- 


22 4 


- 


10 9 


3 


5 9 





Table 59. Computed values of secular change in north component (X) of magnetic field intensity for 1942.5 
at height 5000 km expressed in units of 10-6 CGS per year 



Geographic 
east 












Geographic colatitude 


in 


degrees 












longitude 
in degrees 


10 




20 


30 


40 


50 


60 


70 


80 


90 


30 


_ 


19 


_ 


14 


_ 


5 


4 




12 




17 




16 




9 - 


2 


60 


- 


3 2 


- 


2 6 


- 


15- 


1 




11 




2 3 




2 8 




27 


1 8 


90 


- 


3 3 


- 


2 3 


- 


9 


5 




19 




30 




35 




34 


2 5 


1 20 


- 


2 3 


- 


13 


- 


2 


7 




16 




20 




21 




19 


14 


150 


- 


9 


- 


2 




2 


5 




7 




6 




4 




1 - 


2 


1 80 




6 




7 




6 


4 







- 


4 


- 


10 


- 


16 - 


2 1 


210 




2 




16 




10 


3 


- 


5 


- 


14 


- 


23 


- 


32 - 


3 8 


240 




31 




25 




16 


6 


- 


4 


- 


16 


- 


2 8 


- 


39 - 


47 


270 




37 




3 3 




26 


16 




4 


- 


8 


— 


2 1 


- 


33 - 


42 


300 




3 5 




37 




35 


31 




23 




12 


- 





- 


15 - 


30 


330 




2 3 




2 9 




3 5 


38 




35 




27 




13 


- 


4 - 


2 3 


3 60 




1 




9 




17 


24 




27 




2 3 




14 


- 


o - 


17 




Geographic 
east 












Ge 


ographi 


c colatitude 


in 


degrees 












longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


«. 


15 


a. 


2 7 


a. 


3 2- 


31 


— 


27 


.. 


21 


_ 


18 


m 


17 




60 




3 


— 


1 2 


— 


25 - 


3 1 


— 


33 


- 


31 


- 


31 


— 


31 




90 




10 


- 


6 


- 


2 3- 


36 


- 


44 


- 


47 


- 


47 


- 


43 




120 




6 


- 


3 


- 


15 - 


28 


— 


38 


- 


46 


— 


48 


- 


44 




150 


- 


6 


- 


11 


- 


17 - 


2 3 


— 


29 


- 


3 3 


- 


35 


- 


30 




1 80 


- 


25 


- 


27 


- 


27 - 


2 5 


- 


2 2 


- 


17 


- 


12 


- 


7 




210 


- 


41 


- 


4 2 


- 


37 - 


2 8 


- 


16 


- 


3 




8 




14 




240 


- 


5 2 


— 


52 


- 


47 - 


36 


- 


20 


— 


1 




1 4 




26 




270 


- 


50 


- 


55 


— 


56 - 


50 


— 


37 


_ 


17 




4 




23 




30 


- 


46 


- 


60 


- 


70 - 


70 


- 


60 


- 


40 


- 


14 




11 




330 


- 


43 


- 


60 


- 


71 - 


73 


- 


6 5 


- 


47 


- 


23 









3 60 


— 


33 


— 


46 


— 


5 3- 


5 2 


— 


45 


- 


3 3 


■* 


19 


■* 


7 





51 



Table 60 


. Compute 


d values of 


sec 


ular change 


in east 


component 


(Y 


of magnetic field intensity for 1932.5 






at height 


100 km 


;xpr 


essed in units of 10-6 


CGS pe 


r ye 


ar 






Geographic 
east 










Geographic colatitude 


in 


degrees 










longitude 
in degrees 


lb 


20 


30 


40 


50 


60 


70 


80 


90 


3 


30 l 


32 3 




35 2 




39 8 




45 3 




49 7 




50 7 


4 7 6 


42 1 


60 


7 8 


2 5 


- 


3 


- 


7 4 


- 


9 7 


- 


112 


- 


14 5 


- 216 


- 32 3 


90 


- 13 8 


- 20 3 


- 


26 3 


- 


30 9 


- 


32 7 


- 


31 2 


- 


26 9 


- 213 


- 167 


ISO 


- 27 3 


- 28 2 


- 


25 4 


- 


19 4 


- 


12 4 


- 


6 1 


- 


1 1 


3 8 


10 2 


150 


- 318 


- 29 3 


- 


26 2 


- 


22 4 


- 


18 


- 


137 


- 


9 9 


6 7 


4 1 


1 R 


- 29 1 


- 23 3 


- 


18 8 


- 


15 2 


_ 


113 


- 


6 2 




2 


6 8 


11 4 


310 


- 22 4 


- 16 7 


- 


115 


- 


7 4 


_ 


4 




1 




6 2 


13 8 


213 


2 4 


- 13 2 


- 14 4 


- 


15 3 


- 


15 1 


- 


12 3 


. 


5 7 




37 


12 8 


17 9 


2 7 


9 


4 8 


- 


90 


- 


10 2 


_ 


7 5 


_ 


1 6 




4 8 


8 4 


6 5 


3 


20 2 


16 3 




10 9 




9 


- 


15 4 


- 


36 9 


- 


58 7 


- 74 6 


- 80 3 


3 3 


37 1 


39 1 




39 




34 8 




25 8 




12 9 


- 


5 


- Ill 


- 16 


3 60 


417 


46 9 




50 7 




527 




52 5 




501 




4 6 1 


42 


39 8 




Geographic 
east 










Geographic colatitude 


in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


371 


34 4 




330 




29 4 




190 




1 


_ 


257 


- 517 




60 


- 4 3 7 


- 517 


- 


53 6 


- 


50 3 


- 


45 4 


_ 


4 3 6 


- 


47 1 


- 54 1 




90 


- 14 8 


- 16 2 


- 


20 7 


- 


27 1 


- 


340 


_ 


39 6 


_ 


42 2 


- 40 3 




12 


17 7 


23 8 




25 




19 3 




81 


_ 


3 6 


- 


10 1 


76 




15 


1 9 







2 




4 9 




9 5 




16 2 




24 5 


32 6 




18 


12 8 


118 




115 




15 5 




26 1 




418 




57 4 


66 1 




2 10 


26 8 


29 8 




32 2 




373 




47 1 




60 5 




72 8 


77 6 




2 4 


17 3 


12 6 




8 5 




9 9 




19 3 




34 3 




4 9 4 


58 7 




2 70 


13 


- 12 6 


- 


22 8 


- 


27 4 


- 


2 3 8 


_ 


12 5 




3 4 


19 8 




3 


- 7 5-7 


- 64 9 


- 


53 8 


- 


461 


- 


418 


_ 


37 6 


-. 


29 8 


- 17 2 




3 3 


- 15 


- 10 9 


- 


7 5 


- 


8 2 


- 


141 


_ 


23 4 


- 


32 5 


- 37 9 




3 60 


40 7 


44 




4 6 2 




42 8 




30 1 




7 8 


- 


19 9 


- 4 5 8 




Table 61 


. Compute 


d values of 


secular change 


in east 


component (Y) of magnetic field intensity for 1932.5 






at heig 


ht 


300 km 


expressed in units of 10 _ ° 


CGS pe 


r ye 


ar 






Geographic 
east 










Geographic colatitude 


in 


degrees 










longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


26 6 


287 




31 3 




35 2 




39 8 




43 2 




43 9 


412 


36 6 


60 


6 9 


2 5 


_ 


2 


- 


5 7 


- 


78 


-, 


9 3 


- 


123 


- 18 4 


27 3 


90 


- 12 3 


- 17 8 


- 


22 8 


- 


266 


- 


28 1 


m 


26 9 


- 


23 5 


- 19 1 


- 15 4 


120 


- 24 3 


- 25 


_ 


22 7 


- 


17 7 


- 


117 


_ 


6 3 


- 


17 


2 8 


8 4 


15 


- 28 3 


- 25 9 


- 


230 


- 


19 5 


- 


15 7 


_ 


119 


- 


8 5 


56 


3 2 

100 


180 


- 25 9 


- 20 9 


_ 


16 8 


- 


13 4 


- 


9 8 


_ 


5 2 




3 


6 


210 


- 200 


- 15 2 


_ 


10 7 


- 


70 


- 


37 




2 




5 7 


12 3 


18 7 


24 


- 117 


- 12 6 


- 


132 


- 


12 7 


- 


10 


_ 


4 2 




3 7 


113 


15 7 


2 70 


1 1 


3 9 


_ 


77 


- 


8 9 


- 


70 


_ 


2 6 




2 4 


5 1 


3 5 


30 


18 1 


14 4 




9 2 




2 


- 


13 8 


_ 


31 9 


- 


501 


- 6 3 5 


- 6 8 5 

- 142 
357 


3 3 


32 9 


34 4 




33 8 




29 8 




217 




106 


- 


9 


9 9 


3 60 


36 9 


415 




4 4 8 




46 6 




4 6 4 




44 4 




410 


376 




Geographic 
east 










Geographic 


: colatitude 


in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


32 2 


29 5 




27 9 




24 3 




15 3 


_ 


6 


_ 


21 8 


- 43 




60 


- 367 


.- 43 3 


- 


45 


- 


42 4 


- 


386 


- 


371 


- 


39 7 


- 45 1 




90 


- 13 8 


- 150 


- 


187 


- 


23 8 


- 


29 2 


- 


33 5 


- 


35 3 


- 33 4 




120 


146 


19 5 




20 3 




15 6 




6 4 


- 


2 9 


- 


8,0 


5 9 




15 


11 


7 




2 6 




52 




9 1 




147 




21 3 


27 7 




18 


11 5 


110 




112 




147 




23 5 




36 3 




4 8 7 


55 4 




2 10 


23 4 


261 




28 3 




32 6 




40 5 




51 2 




609 


64 5 




2 4 


15 2 


115 




8 2 




9 4 




16 8 




287 




408 


4 8 3 




2 7 


2 9 


- 12 


- 


20 2 


- 


23 7 


- 


20 6 


~ 


11 1 




2 1 


15 8 




3 


- 65 1 


- 56 5 


- 


47 3 


- 


407 


- 


36 6 


- 


324 


- 


25 4 


- 147 




3 3 


- 136 


- 10 2 


- 


7 3 


- 


77 


- 


12 3 


- 


197 


- 


27 1 


- 315 




3 60 


36 2 


385 




39 9 




36 4 




25 4 




6 7 


*■ 


164 


- 380 





52 



Table 62. Computed values 


of secular change in e; 


ist 


component (Y) of m 


agnetic field intensity for 1932.5 








at height 


500 krr 


expressec 


in 


units of 10- 


6 CGS per 


year 








Geographic 
east 












G 


eograph 


ic colatitude in 


degrees 










longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


23 7 




25 6 




2 8 




31 3 




3 5 




37 8 




3 8 2 




35 9 


31 9 


6 


6 2 




2 5 


- 


1 3 


- 


4 4 


- 


6 2 


- 


7 8 


- 


1 5 


- 


15 8 


- 23 2 


90 


10 9 


- 


15 6 


- 


19 9 


- 


23 


- 


24 2 


- 


23 3 


- 


20 6 


- 


17 


- 14 1 


12 


- 216 


- 


22 2 


- 


20 2 


- 


16 1 


- 


111 


- 


6 3 


- 


2 1 




20 


6 8 


15 


- 25 2 


- 


22 9 


- 


20 3 


- 


17 2 


- 


13 8 


- 


10 4 


- 


73 


- 


47 


2 4 


18 


- 23 1 


- 


18 7 


- 


15 1 


- 


119 


- 


8 6 


- 


4 5 




4 




5 2 


8 8 


2 10 


- 17 8 


- 


13 8 


- 


9 9 


- 


6 5 


- 


3 4 




3 




5 2 




110 


16 5 


240 


- 10 3 


- 


111 


- 


115 


- 


10 8 


- 


8 2 


- 


3 1 




3 6 




100 


137 


2 7 


1 1 


- 


3 3 


- 


6 7 


- 


79 


- 


6 6 


- 


3 2 




6 




2 7 


1 2 


3 


16 1 




12 6 




77 


- 


2 


- 


12 4 


- 


27 8 


- 


43 1 


- 


54 4 


- 587 


3 3 


29 2 




30 3 




29 5 




25 7 




18 5 




8 9 


- 


1 1 


- 


8 8 


- 12 5 


3 6 


32 8 




36 8 




397 




413 




412 




39 5 




36 6 




337 


32 




Geographic 
east 












Geograph 


ic colatitude in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


28 1 




25 6 




23 7 




20 3 




12 4 


_ 


1 


_ 


18 4 


_ 


36 




60 


- 310 


- 


36 4 


- 


3 8 


- 


36 


- 


32 9 


- 


317 


- 


33 7 


- 


37 9 




90 


- 12 9 


- 


13 8 


- 


16 8 


- 


20 9 


_ 


25 3 


- 


28 6 


- 


29 8 


- 


27 9 




ISO 


12 1 




16 




16 6 




12 6 




5 1 


- 


2 4 


- 


6 5 


- 


4 6 




15 


5 




1 1 




30 




5 3 




8 7 




13 3 




187 




237 




1 80 


10 3 




10 3 




10 7 




14 




213 




31 7 




417 




46 8 




a i o 


20 5 




23 




25 




28 6 




35 1 




437 




513 




54 




2 4 


13 4 




10 5 




1 9 




8 8 




147 




24 2 




33 9 




40 1 




2 7 


4 


- 


113 


- 


17 9 


- 


207 


- 


17 9 


- 


100 




1 1 




12 7 




3 


- 56 2 


- 


49 3 


- 


4 18 


- 


360 


- 


32 1 


- 


28 1 


- 


218 


- 


12 6 




3 3 


- 12 2 


- 


9 5 


- 


7 


- 


7 2 


- 


10 8 


- 


16 7 


- 


22 7 


- 


26 5 




3 60 


32 2 




33 8 




34 5 




31 2 




216 




5 7 


- 


13 6 


- 


317 




Table 63 


. Comput 


»d values o 


1 se 


cular change in east component (Y) of magnetic fielc 


intensity for 1932.5 








at he 


ight 


1000 kr 


n expressed in 


units of 10 


-6 CGS 


per year 








Geographic 
east 












Geograph 


ic colatitude in 


degrees 










longitude 
in degrees 


10 


20 


30 


40 


50 


60 




70 




80 


90 


3 


18 




19 6 




214 




23 6 




26 




27 6 




276 




25 9 


23 2 


60 


4 8 




2 4 


- 





- 


2 1 


- 


3 6 


- 


5 


- 


7 2 


- 


10 8 


- 15 8 


90 


8 1 


- 


114 


- 


14 3 


- 


163 


- 


17 2 


_ 


16 7 


- 


15 1 


- 


13 


- 11 3 


12 


- 16 3 


- 


167 


- 


15 5 


- 


12 7 


- 


9 3 


- 


5 8 


- 


2 6 




6 


4 1 


ISO 


- 19 1 


- 


17 3 


- 


15 2 


- 


12 7 


- 


101 


_ 


7 6 


- 


5 2 


- 


3 1 


13 


lfiO 


- 17 7 


- 


14 4 


- 


115 


- 


8 9 


- 


6 2 


- 


3 1 




5 




3 9 


6 6 


2 10 


- 13 7 


- 


10 9 


- 


8 


- 


5 3 


- 


2 6 




4 




4 2 




8 4 


12 3 


2 4 


7 7 


- 


8 3 


- 


8 2 


- 


7 4 


- 


5 2 


_ 


1 5 




3 1 




7 4 


9 9 


2 70 


10 


- 


2 2 


- 


4 8 


- 


60 


- 


5 5 


- 


3 8 


- 


1 8 


- 


8 


18 


3 


12 2 




9 2 




5 2 


- 


9 


- 


. 9 6 


- 


200 


- 


30 2 


- 


37 8 


- 411 


3 3 


219 




22 3 




213 




18 1 




12 7 




5 8 


_ 


1 1 


- 


6 5 


9 3 


3 60 


247 




27 7 




29 8 




30 9 




30 9 




29 7 




27 8 




25 8 


24 5 




Geographic 
east 












Geograph 


ic colatitud 


3 in 


degree 


s 










longitude 
in degrees 


100 


110 


120 




130 


140 


150 


160 


170 




3 


20 4 




18 2 




16 2 




13 3 




7 6 


_ 


1 3 


_ 


12 6 


_ 


23 8 




60 


- 20 8 


- 


24 3 


- 


25 4 


- 


24 4 


- 


22 6 


- 


218 


- 


22 9 


- 


25 




90 


- 105 


- 


112 


- 


12 9 


- 


15 4 


- 


17 9 


_ 


19 7 


_ 


200 


- 


18 2 




12 


7 5 




10 




10 2 




76 




30 


- 


1 5 


- 


3 8 


- 


2 4 




ISO 


3 




1 8 




3 3 




5 1 




7 4 




10 4 




137 




16 6 




1 B 


8 




8 5 




9 3 




118 




16 6 




23 




28 9 




31 6 




2 10 


15 2 




17 




18 6 




21 1 




25 1 




30 2 




34 5 




35 7 




2 40 


9 9 




8 2 




6 7 




7 2 




10 7 




16 3 




22 1 




25 8 




2 70 


5 1 


- 


96 


- 


13 5 


- 


14 9 


- 


12 9 


_ 


7 6 


- 


2 




7 4 




30 


- 39 9 


- 


35 8 


- 


310 


- 


26 9 


- 


237 


- 


20 2 


- 


15 4 


- 


90 




3 30 


9 3 


- 


77 


- 


6 1 


- 


60 


- 


8 


- 


115 


- 


15 2 


- 


17 7 




3 60 


24 3 




24 8 




24 4 




21 5 




146 




3 8 


- 


8 9 


- 


20 9 





53 



Table 64. Computed values of secular change in east component (Y) of magnetic field intensity for 1932.5 
at height 5000 km expressed in units of 1G~6 CGS per year 



Geographic 
east 








Geographic colatitude 


in 


degrees 










longitude 
in degrees 


10 


20 


30 


40 




50 


60 


70 


80 


90 


30 


3 3 


36 


39 




4 2 




43 




43 




42 


39 


36 


60 


12 


10 


7 




5 




2 


- 


1 


- 


4 


9 


14 


90 


10 


- .14 


18 


- 


2 1 


- 


2 2 


- 


3 3 


- 


2 3 


2 2 


2 2 


120 


26 


27 


27 


- 


2 4 


- 


2 1 


m 


17 


- 


1 2 


7 


3 


150 


3 2 


30 


2 6 


- 


21 


- 


16 


- 


11 


- 


7 


2 


1 


1 80 


3 1 


2 6 


20 


- 


1 4 


- 


8 


- 


2 




3 


8 


13 


210 


2 5 


20 


15 


- 


9 


_ 


3 




3 




9 


1 5 


2 1 


24 


14 


14 


12 


- 


10 


- 


5 


- 


1 




3 


8 


11 


270 





5 


9 


- 


1 3 


» 


1 5 


- 


17 


- 


17 


19 


20 


300 


1 8 


11 


3 


- 


6 


- 


17 


_ 


2 8 


- 


39 


47 


5 2 


330 


35 


3 3 


29 




2 3 




16 




7 


- 





7 


12 


3 60 


4 2 


46 


49 




50 




50 




49 




47 


44 


41 






























Geographic 
east 








Geographic colatitude 


in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


UO 


150 


160 


170 




30 


31 


26 


20 




1 3 




5 


— 


3 


_ 


14 


2 3 




60 


18 


2 1 


2 3 


- 


2 4 


— 


23 


■- 


2 3 


- 


2 3 


2 3 




90 


2 2 


2 2 


2 2 


- 


2 3 


- 


2 2 


- 


21 


- 


1 8 


14 




120 





2 


3 




2 







- 










3 




150 


5 


9 


1 2 




1 5 




1 8 




20 




2 2 


2 3 




180 


17 


2 1 


2 4 




2 8 




3 2 




3 5 




37 


36 




210 


2 5 


2 9 


31 




3 4 




36 




3 7 




3 8 


3 6 




240 


1 2 


1 2 


1 2 




1 3 




14 




17 




1 9 


2 1 




270 


2 2 


2 4 


2 5 


- 


2 4 


- 


20 


_ 


1 5 


- 


7 







30 


54 


5 2 


4 8 


_ 


43 


- 


37 


- 


30 


- 


2 3 


15 




3 30 


14 


15 


15 


- 


1 5 


- 


1 5 


-> 


17 


- 


1 9 


2 1 




3 60 


38 


34 


2 9 




2 2 




12 




1 


- 


11 


22 




Table 6 


5. Comput 


ed values o 


f secular c 


tiange in east component (Y) of magnel 


ic fielc 


intensity for 1942.5 






at hei 


ght 100 km 


expressed 


in units of 


10- 


5 CGS per y« 


>ar 






Geographic 
east 








Ge 


ographi 


c colatitude 


in 


degrees 










longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


25 4 


27 3 


29 5 




32 1 




34 6 




35 9 




34 9 


31 5 


26 7 


60 


R 6 


60 


1 9 


- 


2 6 


- 


6 9 


- 


112 


- 


16 9 


- 25 2 


- 36 4 


90 


9 7 


- 13 6 


- 1 R 7 


- 


24 1 


- 


2 8 


- 


28 3 


- 


24 6 


- 18 6 


- 13 6 


12 


- 23 3 


- 24 4 


- 2 3 7 


- 


211 


- 


16 3 


- 


9 4 


- 


5 


9 5 


18 9 


150 


- 29 


- 27 3 


- 2 4 6 


- 


211 


- 


17 5 


- 


13 9 


- 


10 2 


6 3 


2 3 


1 8 


- 26 7 


- 219 


- 16 


- 


9 9 


- 


4 5 









4 


7 7 


112 


2 10 


- 19 3 


- 14 7 


9 3 


- 


3 a 




1 9 




8 




14 2 


20 2 


25 4 


2 4 


O 2 


9 3 


- 1 4 


- 


118 


- 


115 


- 


80 


- 


1 4 


6 4 


12 9 


2 70 


3 3 


1 


3 


- 


3 7 


- 


1 7 




2 2 




5 7 


5 9 


1 3 


3 


17 4 


12 8 


6 3 


- 


2 9 


- 


15 4 


- 


301 


- 


4 4 2 


- 54 4 


- 58 


3 3 


29 3 


2B 6 


27 




23 6 




17 5 




R 8 


- 


8 


R 4 


- 112 


3*0 


33 2 


367 


4 12 




45 5 




47 8 




4 6 




39 8 


31 6 


25 1 




Geographic 
east 








Ge 


ographi 


c colatitude 


in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


218 


17 6 


13 4 




7 1 


_ 


3 7 


_ 


19 9 


_ 


39 9 


- 597 




60 


- 4 5 


- 5 R 6 


- f, 4 4 


- 


65 1 


- 


62 5 


- 


59 2 


- 


56 9 


- 55 5 




9 


- 12 9 


- 1 7 R 


- 27 1 


- 


37 4 


- 


44 8 


- 


4 6 4 


- 


415 


- 314 




12 


2 5 


25 8 


2<"> 8 




12 




3 5 


- 


5 




2 1 


10 9 




1 5 


1 5 


5 3 


9 6 




15 6 




24 4 




3 5 5 




47 1 


5 5 2 




1 P. 


14 7 


19 


25 3 




35 3 




4 9 2 




65 1 




7 8 3 


83 1 




2 10 


2 9 6 


33 6 


3 R 8 




4 6 6 




57 4 




6 9 2 




7 R 3 


R 8 




2 4 


15 9 


15 6 


14 5 




1 5 6 




2 Q 




2 9 9 




4 1 


4 8 5 




2 7 


7 6 


- 1 R 


- 26 7 


- 


30 6 


- 


2 n 7 


- 


214 


- 


1 


3 6 




3 


- 54fl 


- 4 7 4 


- 3 9 R 


- 


35 3 


- 


3 4 8 


- 


36 2 


- 


36 1 


- 314 




3 3 


R 2 


15 


4 7 




5 5 


- 


1 6 


- 


1 6 1 


- 


33 7 


- 4 8 6 




3 60 


23 3 


26 3 


30 7 




3 6 




20 8 




1 


- 


27 7 


- 55 5 





54 



Table 66. Computed values of secular change in east component (Y) of magnetic field intensity for 1942.5 
at height 300 km expressed in units of 10"" CGS per year 



Geographic 
east 








Geograph 


ic colatitude 


■ in 


degrees 








longitude 


10 


20 


30 




40 


50 




60 




70 


80 


90 


in degrees 


























3 


P.P 4 


24 3 


26 2 




2 R 4 


30 4 




312 




301 


27 


22 7 


60 


7 4 


5 1 


1 7 


- 


2 1 


5 8 


- 


9 7 


- 


147 


- 219 


- 313 


9 


R a 


- 12 3 


- 16 6 


- 


211 


- 24 2 


- 


24 4 


- 


21 5 


- 167 


- 12 8 


ISO 


- ?0 7 


- 216 


- 211 


- 


18 8 


- 14 7 


- 


R7 


- 


9 


76 


15 6 


15 


- ?54 


- 23 9 


- 214 


- 


1 R 4 


- 15 1 


- 


118 


- 


8 5 


5 


14 


18 


- 23 4 


- 19 1 


- 14 


- 


R 7 


3 9 




2 




3 8 


71 


103 


3 10 


- 17 


- 130 


R 4 


- 


3 4 


1 6 




6 9 




12 4 


17 8 


22 4 


?40 


R 1 


8 2 


9 


- 


9 7 


9 1 


- 


5 9 


- 


3 


6 2 


115 


3 7 


2 9 


2 


2 8 


- 


3 6 


2 2 




7 




3 3 


3 4 


4 


30 


15 3 


111 


5 4 


- 


2 7 


- 13 4 


- 


25 8 


- 


37 7 


- 46 3 


- 4 9 5 


330 


25 9 


25 2 


23 7 




20 5 


15 




7 3 


- 


9 


7 4 


9 9 


3 6 


P 9 5 


32 6 


36 4 




40 


417 




4 1 




34 9 


2ft 1 


22 7 




Geographic 
east 








Geograph 


c colatitude 


in 


degrees 










longitude 


100 


110 


120 




130 


140 




150 




160 


170 




in degrees 


























3 


1 R 3 


14 4 


10 4 




4 7 


4 5 


_ 


181 


_ 


346 


- 50 9 




60 


- 4 14 


- 4 9 8 


- 54 8 


- 


55 7 


- 53 7 


- 


510 


- 


4 9 1 


- 47 7 




9 


- 12 4 


- 16 5 


- 24 2 


- 


32 7 


- 38 7 


_ 


39 9 


_ 


35 8 


- 27 2 




IPO 


20 7 


21 3 


17 2 




100 


2 9 


- 


4 




1 7 


R 8 




1 5 


2 1 


5 6 


9 4 




14 7 


22 




312 




40 3 


46 7 




1 R 


13 6 


17 5 


23 1 




317 


43 3 




56 3 




66 9 


70 4 




210 


26 3 


29 9 


34 4 




4 10 


4 9 9 




59 4 




66 7 


6 8 5 




P 4 


14 


13 9 


13 1 




14 1 


18 4 




25 ft 




34 2 


413 




P. 7 


7 6 


- 16 1 


- 23 


- 


26 


- 24 2 


- 


17 9 


- 


fll 


3 5 




3 


- 47 2 


- 413 


- 35 1 


- 


31 2 


- 303 


- 


30 9 


- 


30 2 


- 25 9 




3 3 


7 6 


2 1 


2 8 




3 6 


2 2 


- 


13 9 


- 


28 3 


- 4 06 




3 6 


211 


23 3 


26 3 




25 6 


16 9 


- 


4 


- 


23 7 


- 4 6 9 




Table 67 


Compute 


d values of 


secular ch; 


inge 


in eas 


component (Y) of magnetic field 


ntensity f or 1942.5 






at hei{ 


;ht 500 km « 


»xpr 


essed in units of 10 -6 


CGS pei 


" year 






Geographic 
east 








Geographic colatitude 


in 


degrees 










longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


19 9 


21 6 


23 4 




25 2 


26 8 




27 3 




26 1 


23 3 


19 4 


60 


6 5 


4 5 


1 5 


- 


1 7 


5 


- 


85 


- 


12 9 


- 19 1 


- 270 


oO 


R 


- Ill 


- 14 8 


- 


18 5 


- 210 


- 


212 


- 


18 8 


- 15 


- 12 


1 P. 


- 1 R 4 


- 19 3 


- 1 R R 


- 


16 9 


- 132 


- 


RO 


- 


1 2 


6 1 


12 8 


150 


- 22 5 


- 210 


- 1 R 8 


- 


16 


- 131 


- 


101 


- 


7 1 


3 9 


6 


1 P, 


- 20 6 


- 16 8 


- 12 3 


- 


77 


3 4 




2 




3 5 


6 6 


9 5 


no 


- 15 


- 115 


7 5 


- 


3 2 


1 3 




60 




10 9 


157 


19 8 


P 4 


7 2 


7 3 


77 


- 


8 1 


73 


- 


4 4 




4 


5 9 


10 3 


270 


2 5 


3 


2 6 


- 


3 5 


2 5 


- 


2 




1 6 


1 5 


16 


3 


13 5 


9 8 


4 6 


- 


2 5 


- 117 


- 


22 3 


- 


32 4 


- 397 


- 42 5 


3 3 


23 


22 4 


20 8 




17 9 


12 9 




6 2 


- 


9 


6 5 


8 7 


3 6 


2 6 2 


29 1 


32 3 




35 2 


36 5 




35 




307 


25 1 


20 6 




























Geographic 
east 








Geographi 


c colatitude 


in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


15 4 


118 


R 1 




30 


4 9 


_ 


16 4 


_ 


30 2 


- 43 8 




60 


- 35 5 


- 42 7 


- 4 6 9 


- 


47 8 


- 46 4 


- 


44 3 


_ 


42 5 


- 412 




90 


- 11 R 


- 15 3 


- 217 


- 


2 8 6 


- 33 5 


- 


34 5 


_ 


310 


- 23 7 




IPO 


17 2 


17 7 


14 3 




R 3 


2 5 


- 


2 




1 4 


7 2 




15 


2 5 


5 7 


9 2 




13 7 


19 9 




27 4 




34 8 


39 8 




1 ft 


12 6 


16 1 


211 




28 5 


38 3 




49 




57 5 


60 1 




P. 1 


23 3 


26 6 


30 6 




36 3 


43 6 




514 




57 2 


58 5 




3 4 


12 4 


12 4 


118 




12 8 


16 4 




22 5 




2 9 4 


35 4 




P 70 


7 5 


- 14 3 


- 19 9 


- 


22 2 


- 20 5 


- 


15 


_ 


66 


3 4 




3 


- 40 8 


- 36 1 


- 310 


- 


27 6 


- 26 5 


- 


26 5 


_ 


25 5 


- 216 




3 30 


6 9 


2 5 


1 5 




2 1 


2 5 


- 


12 2 


_ 


24 


- 34 3 




3 60 


19 1 


20 6 


22 6 




21 5 


139 


- 


8 


- 


20 4 


- 399 





55 



Table 68. 



Computed values of secular change in east component (Y) of magnetic field intensity for 1942.5 
at height 1000 km expressed in units of 10~6 CGS per year 



Geographic 
east 








Geograph 


ic colatitud 


e in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 




50 




60 


70 


80 


90 


3 


149 


16 4 


17 7 




18 9 




19 7 




19 8 




187 


16 4 


13 5 


60 


4 7 


3 3 


1 2 


- 


1 1 


- 


3 5 


- 


6 1 


- 


9 4 


- 13 8 


- 19 2 


9 


6 2 


8 6 


- Ill 


- 


13 6 


- 


15 1 


- 


15 2 


- 


13 8 


- 116 


- lOO 


12 


- 13 8 


- 14 6 


- 14 3 


- 


12 9 


- 


10?, 


- 


6 4 


- 


1 7 


3 5 


80 


15 


- 167 


- 15 5 


- 13 8 


- 


117 


- 


9 4 


- 


7 1 


- 


4 6 


2 1 


4 


1 B0 


- 15 3 


- 12 4 


9 1 


_ 


5 7 


- 


2 4 




4 




3 


5 5 


7 8 


?! 1 


- Ill 


8 6 


5 6 


- 


2 4 




9 




4 5 




8 2 


117 


14 9 


2 4 


5 4 


5 4 


5 4 


- 


5 2 


- 


4 2 


- 


2 




1 3 


5 


7 9 


2 70 


1 8 


3 


2 2 


- 


3 1 


- 


2 7 


- 


1 7 


_ 


7 


10 


3 1 


3 


10 1 


7 1 


3 2 


- 


1 9 


- 


8 5 


- 


15 8 


- 


22 7 


- 27 7 


- 29 9 


3 3 


17 3 


16 8 


15 4 




12 9 




9 1 




4 2 


- 


8 


4 8 


6 4 


3 60 


19 7 


219 


24 1 




25 9 




26 6 




25 5 




22 6 


190 


16 






























Geographic 
east 








Geograph 


c colatitude in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


10 3 


7 4 


4 3 




4' 


_ 


5 2 


_ 


12 9 


_ 


22 


- 307 




60 


- 24 8 


- 29 7 


- 32 6 


- 


33 5 


- 


32 9 


- 


31 6 


- 


30 4 


- 29 2 




9 


- 101 


- 12 5 


- 16 6 


- 


210 


- 


24 1 


- 


24 5 


- 


22 


- 170 




12 


10 9 


113 


9 2 




5 4 




1 7 


- 






9 


4 6 




15 


2 9 


5 4 


8 1 




114 




15 5 




20 3 




24 7 


27 4 




180 


10 3 


13 2 


16 9 




22 1 




2 8 7 




35 4 




40 5 


415 




2 1 


17 6 


20 2 


2 3 2 




27 1 




31 8 




36 6 




40 


40 6 




2 4 


9 4 


9 5 


9 3 




10 




12 3 




16 3 




207 


24 8 




2 70 


6 8 


- 10 9 


- 14 2 


- 


15 4 


- 


14 


- 


100 


- 


4 1 


3 




3 


- 29 1 


- 26 3 


- 23 1 


- 


20 6 


- 


19 3 


- 


18 6 


- 


172 


- 142 




3 3 


5 5 


2 8 


4 


- 




- 


2 9 


- 


90 


- 


16 4 


- 23 1 




3 60 


147 


15 1 


15 7 




14 1 




8 4 


— 


1 6 


— 


14 6 


- 27 5 




Table 6 


9. Compu 


:ed values < 


Df secular c 


hange in east component (Y) of magnetic field intensity for 1942.5 






at he 


ight 5000 k 


m expressed in 


units of 10 


-b CGS 


per 


year 






Geographic 
east 








Geograph 


c colatitude in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


2 4 


2 6 


2 8 




2 9 




2 9 




27 




24 


20 


15 


60 


7 


5 


2 







. 


4 


- 


9 


- 


14 


20 


26 


90 


10 


14 


18 


_ 


21 


a 


2 2 


- 


2 3 


- 


3 3 


2 3 


24 


120 


2 2 


24 


24 


- 


22 


™ 


19 


- 


14 


_ 


9 


3 


1 


150 


26 


2 4 


20 


m 


16 


_ 


1 2 


- 


7 


_ 


3 


3 


8 


1 80 


2 3 


18 


12 


- 


6 


«, 


1 




4 




10 


1 5 


21 


210 


16 


12 


7 


- 


1 




4 




11 




17 


3 3 


2 8 


24 


8 


7 


6 


- 


3 


_ 







2 




6 


10 


1 3 


2 70 


2 


1 


5 


m 


7 


_ 


10 


- 


1 1 


_ 


12 


14 


15 


3 


1 5 


10 


3 


- 


4 


_ 


1 3 


- 


21 


_ 


2 9 


3 5 


3 9 


330 


27 


2 5 


2 2 




17 




11 




5 


- 





6 


9 


3 60 


3 1 


3 5 


37 




3 8 




3 8 




36 




3 3 


29 


2 5 




Geographic 
east 








Geograph 


lc colatitud 


2 in 


degree 


s 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


9 


3 


3 




10 


_ 


1 8 


_ 


27 


— 


35 


43 




60 


3 2 


37 


41 


- 


4 3 


= 


44 


- 


4 3 


- 


42 


40 




90 


2 5 


27 


30 


. 


3 2 


_ 


33 


- 


32 


- 


2 9 


3 3 




120 


4 


5 


4 




3 




1 




1 




2 


5 




150 


1 3 


1 8 


2 2 




26 




30 




34 




36 


36 




1 80 


27 


32 


3 8 




44' 




50 




5 4 




56 


5 4 




210 


3 3 


3 8 


43 




47 




5 1 




5 3 




54 


53 




34 


16 


17 


1 9 




20 




23 




2 6 




30 


3 4 




270 


17 


19 


19 


_ 


1 8 


_ 


14 


— 


8 


- 


1 


7 




3 


40 


3 9 


36 


- 


3 3 


_ 


2 9 


- 


2 5 


- 


2 1 


15 




330 


10 


11 


11 


- 


12 


_ 


14 


- 


19 


- 


3 4 


3 9 




3 60 


2 2 


1 8 


1 3 




7 


- 


1 


— 


1 3 


- 


26 


3 8 





56 



Table 70. Computed values of secular change in vertical component (Z) of magnetic field intensity for 1932.5 
at height 100 km expressed in units of 10-6 CGS per year 



Geographic 
east 










Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


_ 


17 4 


7 1 


33 6 




5 2 5 


55 4 




403 


14 4 


8 1 


- 13 4 


60 


- 


112 


17 1 


4 5 6 




69 


813 




77 6 


57 1 


26 9 


2 


90 


- 


115 


12 3 


317 




43 


4 3 9 




32 1 


6 2 


- 30 6 


- 6 7 4 


1 20 


- 


17 


6 


117 




18 2 


18 6 




12 9 


2 1 


- 10 7 


- 19 7 


15 


- 


25 7 


- 17 2 


9 A 


- 


1 7 


3 3 




1 1 


- 1 5 


- 2 6 1 


- 33 9 


1 a o 


_ 


35 3 


- 34 


- 3R 4 


- 


29 6 


- 26 3 


- 


2 6 


- 318 


- 415 


- 47 5 


RIO 


- 


4 3 9 


- 4 6 9 


- 4 6 3 


- 


43 1 


- 38 4 


- 


32 8 


- 27 8 


- 23 2 


- 17 2 


2 4 


- 


50 6 


- 59 


- 62 1 


- 


618 


- 57 8 


- 


4 8 1 


- 32 3 


- 13 7 


3 2 


2 7 


_ 


54 


- 6 8 9 


- 79 7 


- 


8 2 9 


- 715 


- 


40a 


3 4 


4 4 2 


6 3 7 


3 


- 


513 


- 65 9 


- 7 8 


- 


84 


- 7 8 5 


- 


58 3 


- 2 8 


8 


9 1 


3 3 


- 


4 19 


- 45 7 


- 4 8 4 


- 


55 7 


- 718 


- 


9 3 7 


- 1 12 8 


-1 20 4 


-114 8 


3 60 


- 


R8 9 


- 16 6 


2 6 




3 3 


7 1 


- 


32 9 


- 6 3 3 


- R 3 9 


- 85 7 




Geographic 
east 










Geographic colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 




4 9 


4 19 


83 3 




113 4 


12 2 7 




1119 


9 0S 


70 9 




60 


- 


1 R 


211 


6 6 




9 4 9 


104 9 




R fl 4 


618 


4 8 6 




90 


- 


R7 4 


- 78 9 


- 45 7 


- 


6 5 


17 5 




20 1 


15 1 


25 2 




12 


- 


19 3 


8 9 


3 5 




7 3 


2 2 


- 


16 3 


- 167 


10 5 




15 


- 


24 9 


2 4 


18 1 




20 9 


4 


- 


16 2 


- 17 


12 6 




18 


- 


416 


- 22 9 


1 




14 8 


16 9 




12 5 


15 


32 6 




RIO 


- 


6 8 


1 O 1 


32 4 




55 


712 




76 5 


72 


64 1 




R 4 




17 


32 3 


55 9 




8 8 5 


1207 




136 7 


126 2 


94 6 




R 7 




57 9 


42 3 


413 




68 5 


113 6 




14 8 4 


14 8 6 


112 3 




3 0O 


- 


6 


- 167 


- 16 6 




13 7 


67 5 




118 1 


137 


113 6 




3 3 


- ; 


L 00 3 


- 80 6 


- 53 6 


- 


14 1 


37 1 




86 7 


113 5 


103 5 




3 60 


- 


6 9 5 


- 4 16 


R 4 




26 9 


614 




88 6 


99 3 


8 8 7 




Table 71. 


Computed 


values of s 


ecular chan 


ge 


in vertic 


al component (Z) of m 


agnetic field intensity for 1932.5 








at hei£ 


;ht 300 km 


expressed in units of lO" 6 CGS pe 


r year 






Geographic 
east 










Geographic colatitude 


in 


degrees 








longitude 




10 


20 


30 




40 


50 




60 


70 


80 


90 


in degrees 


























3 


_ 


15 4 


5 8 


R 8 4 




4 4 2 


4 6 7 




34 


12 6 


5 9 


- 100 


60 


- 


9 9 


14 8 


39 6 




59 5 


6 9 7 




6 6 1 


4 8 6 


23 4 


2 9 


90 


- 


10 R 


107 


27 7 




37 7 


3 8 3 




27 9 


5 5 


- 25 6 


- 56 1 


12 


- 


15 2 


9 


9 9 




15 7 


15 9 




107 


10 


- 101 


- 1 R 


15 


- 


23 1 


- 15 6 


8 8 


- 


2 5 


1 4 


- 


7 


- 103 


- 22 9 


- R 8 9 


180 


- 


316 


- 30 6 


- 29 1 


- 


26 7 


- 2 4 2 


- 


24 2 


- 28 9 


- 36 6 


- 40 9 


RIO 


- 


39 3 


- 4 2 4 


- 42 1 


- 


39 4 


- 35 3 


- 


30 4 


- 25 8 


- 213 


- 15 4 


2 4 


- 


45 3 


- 53 2 


- 56 2 


- 


55 7 


- 517 


- 


4 2 5 


- 2 8 3 


- 117 


3 4 


2 7 


- 


4 8 1 


- 615 


- 70 8 


- 


7 3 1 


- 62 6 


- 


36 2 


1 1 


35 6 


52 8 


3 


- 


4 5 6 


- 58 7 


- 6 9 2 


- 


7 4 4 


- 6 9 7 


- 


52 6 


- 27 3 


4 5 


4 5 


3 3 


- 


37 2 


- 4 10 


- 4 4 1 


- 


5 10 


- 6 4 8 


- 


8 3 1 


- 9 8 7 


-10 5 1 


_ 3 O O 4 


3 6 


- 


25 7 


- 15 4 


4 1 






9 1 


- 


310 


- 56 4 


- 73 5 


- 74 9 




Geographic 
east 










Geographii 


: colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 




5 5 


36 6 


716 




97 5 


1 6 R 




98 2 


812 


6 5 5 




60 







19 3 


52 2 




80 8 


89 9 




77 6 


57 


4 6 9 




90 


- 


7R 3 


- 64 8 


- 37 


- 


4 2 


16 5 




20 2 


17 8 


27 4 




12 


- 


17 8 


9 2 


1 3 




5 3 


9 


- 


1 4 


8 6 


15 2 




150 


- 


21 3 


2 9 


13 9 




16 8 


4 5 


- 


100 


R 7 


16 9 




1 R 


- 


35 3 


- 19 2 


2 




13 5 


16 7 




14 7 


181 


33 5 




RIO 


- 


5 6 


9 6 


29 2 




4 8 9 


63 2 




6 8 5 


65 5 


59 5 




R 4 




16 2 


30 3 


510 




78 6 


1 5 4 




118 7 


1 102 


84 6 




R 7 




49 7 


38 8 


396 




627 


99 8 




12 8 2 


12 8 5 


9 9 1 




3 


- 


2 


- 13 3 


- 112 




15 3 


6 4 




10 2 8 


119 


3 00 2 




3 30 


- 


87 7 


- 6 9 9 


- 45 2 


- 


10 


34 4 




76 8 


99 9 


9 2 




3 60 


- 


6 0R 


- 36 2 


6 5 




25 1 


55 5 




7 9 2 


8 8 6 


80 1 





57 



Table 72. Computed values of secular change in vertical component (Z) of magnetic field intensity for 193?. 5 
at height 500 km expressed in units of 10 _ 6 CGS per year 



Geographic 
east 














Geographic colatitude in 


degrees 




longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


_ 


13 8 




4 7 




24 




37 4 39 4 


289 110 - 43 


7 5 


60 


_ 


8 9 




12 8 




34 3 




5 14 5 9 9 


566 415 204 


3 8 


90 


_ 


9 2 




9 2 




24 2 




3 3 3 3 5 


343 49 - 316 


- 4 7 


13 


_ 


13 7 


- 


1 1 




a 4 




13 4 13 6 


8 9 3 - 9 6 


- 16 4 


15 


_ 


20 7 


- 


14 3 


- 


8 4 


- 


3 1 - 


30 _ 101 - 303 


- 2 4 9 


1 B0 


_ 


28 4 


- 


27 7 


- 


26 3 


- 


343 - ?22 - 


224 - 264 - 32 4 


- 35 4 


R10 


_ 


35 4 


- 


38 5 


- 


3 8 4 


- 


361 - 325 - 


281 - 238 - 194 


- 13 7 


3 4 


_ 


4 07 


- 


4 8 1 


- 


5 1 


- 


50 5 - 464 - 


378 - 249 - 102 


3 4 


3 7 


_ 


43 1 


- 


55 1 


- 


6 3 2 


- 


648 - 55 3 - 


323- 5 288 


4 4 1 


3 


_ 


4 7 


- 


53 4 


- 


6 18 


- 


663 - 632 - 


477 - 263 - 70 


1 2 


3 3 


_ 


33 2 


- 


36 9 


- 


4 3 


- 


467 - 586 


74O - 870 - 933 


- 8 8 1 


3 60 


- 


3 3 9 


- 


14 3 


- 


5 2 


- 


2 3 _ 105 - 


391 - 505 - 648 


- 6 5 8 




Geographic 
east 














Geographic colatitude in 


degrees 




longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 




5 8 




32 1 




619 




84 3 93 4 


866 731 603 




60 




1 3 




17 6 




4 5 3 




6 9 4 77 7 


6 81 534 448 




90 


- 


60 1 


- 


53 6 


- 


301 


- 


3 4 15 7 


20 194 285 




120 


- 


16 3 


- 


9 3 


- 


1 




39 1 - 


59- 27 183 




15 


- 


18 4 


- 


3 3 




10 8 




13 8 4 9- 


54- 26 198 




18 


- 


30 1 


- 


162 




5 




12 5 16 3 


161 200 335 




3 10 


- 


4 6 




9 1 




36 4 




4 3 8 5 6 5 


616 5 97 552 




3 4 




15 3 




28 3 




4 6 5 




70 1 Q2 6 


1037 969 760 




3 7 




4 3 




35 6 




37 6 




5 7 4 8 8 1 


1116 1119 880 




3 


- 


3 


- 


10 6 


- 


7 2 




16 1 5 4 4 


900 1039 889 




3 3 0, 


- 


77 


- 


6 0fi 


- 


3 8 3 


- 


6 9 319 


684 883 823 




3 60 


- 


53 3 


- 


315 


- 


5 




23 2 50 2 


710 793 72 5 




Table 73. 


Computed 


vali 


jes of secular change 


n vertical component (Z) of magnetic field intensity for 1932.5 










at he 


ight 


1000 km expressed in units of 10 


-6 CGS per year 




Geographic 
east 














Geographic colatitude in 


degrees 




longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


_ 


10 9 




2 4 




15 7 




2 4 8 26 2 


193 78- 18 


3 5 


60 


- 


7 1 




8 8 




24 2 




36 2 4 18 


392 289 149 


4 1 


90 


- 


7 4 




6 3 




17 4 




2 3 9 24 2 


174 38 -143 


- 30 8 


12 


- 


10 9 


- 


1 5 




5 5 




9 2 9 2 


5 5 - 8 - 8 


- 12 9 


15 


- 


16 3 


- 


116 


- 


73 


- 


3 9 - 2 2 - 


38- 91 -153 


- 17 7 


18 


- 


33 3 


- 


219 


- 


20 9 


- 


194 - 183 - 


186 - 311 - 244 


- 25 3 


3 10 


- 


376 


- 


30 5 


- 


30 8 


- 


293- 266 - 


232 - 195 - 15 6 


- 10 4 


3 4 


- 


316 


- 


37 8 


- 


4 3 


- 


396 - 359 - 


287 - 187 - 74 


3 3 


3 70 


- 


33 3 


- 


43 5 


- 


4 8 4 


- 


489 - 415 - 


25 1 - 32 171 


2 8 7 


3 


- 


313 


- 


40 3 


- 


47 3 


- 


505 - 476 - 


378 - 235 - 103 


3 6 


3 3 


- 


35 6 


- 


29 


- 


32 4 


- 


37 7 - 4 6 1 - 


563 - 647 - 679 


- 64 8 


3 60 


- 


17 8 


- 


13 3 


- 


6 8 


- 


5 7 - 119 - 


246 - 387 - 480 


- 4 8 3 




Geographic 
east 














Geographic colatitude in 


degrees 




longitude 
in degrees 




100 




110 




120 




130 


140 




150 


160 


170 
































3 




5 7 




23 6 




4 4 




59 9 66 7 


64 5 569 492 




60 




3 3 




18 2 




32 5 




4 8 9 5 5 5 


513 428 391 




90 


_ 


38 7 


- 


33 8 


- 


181 




5 137 


187 207 283 




13 


- 


130 


- 


8 3 


- 


1 8 




2 1 19 


10 6 216 




150 


- 


13 3 


- 


3 4 




5 8 




8 9 5 4 


17 6 3 22 6 




18 


_ 


30 8 


- 


10 7 




1 2 




10 5 15 


171 216 316 




2 10 


_ 


2 8 




7 9 




20 8 




33 7 4 3 3 


479 477 456 




24 




13 




33 6 




37 1 




5 3 5 6 8 5 


758 718 590 




3 7 




30 5 




38 5 




32 1 




4 6 660 


810 814 66 6 




3 


- 


4 1 


- 


6 1 


- 


1 




16 3 42 4 


662 761 673 




3 30 


- 


56 4 


- 


4 3 6 


- 


257 


- 


18 36 4 


521 663 632 




3 6 


- 


38 9 


- 


22 6 


- 


2 4 




19 1 39 3 


545 610 571 





58 



Table 74. 



Computed values of secular change in vertical component (Z) of magnetic field intensity for 193?. 5 
at height 5000 km expressed in units of 10-6 CGS per year 



Geographic 
east 


Geographic colatitude in degrees 


longitude 




10 




20 


30 


40 


50 


60 


70 


80 


90 


in degrees 
























30 


— 


3 8 




20 


-4 6 10 83 4 


60 


- 


30 


_ 


5 


17 34 42 41 34 26 22 


90 


- 


2 9 


_ 


6 


12 24 27 21 8- 6-17 


120 


- 


3 5 


_ 


19 


7- o- 3-10-18-22 


150 


- 


45 


_ 


37 


31 - 27 - 26 - 27 - 30 - 31 - 28 


180 


- 


5 6 


- 


57 


56 - 54 - 52 - 51 - 49 - 44 - 36 


210 


- 


6 6 


_ 


74 


76 - 74 - 69 - 60 - 48 - 34 - 17 


24 


- 


73 


_ 


86 


-91-88-78-62-40-16 8 


270 


- 


76 


_ 


9 2 


- 101 - 9 9 - 87 - 6 5 - 3 6 - 7 18 


30 


- 


7 2 


- 


89 


- 101 - 106 - 103 - 92 - 75 - 56 - 37 


330 


- 


6 3 


_ 


7 3 


83 - 94 - 104 - H3 - 117 - 115 - 103 


3 60 


- 


50 


- 


47 


45 - 48 - 56 - 67 - 76 - 80 - 72 




Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 




9 




40 


65 8 9 107 117 121 12 2 


60 


_ 


2 




39 


58 77 92 101 107 113 


90 


- 


19 


_ 


10 


7 29 51 70 87 104 


120 




8 


- 


12 


15 32 51 74 98 


15 




7 


_ 


8 


6 21 36 54 75 99 


180 


- 


2 2 


_ 


4 


16 37 57 74 91 108 


210 


_ 


25 




27 


51 74 94 107 116 119 


24 




4 




5 8 


83 106 125 13 5 136 130 


270 




40 




5 9 


80 102 • 124 139 143 136 


30 




10 




2 


29 61 95 122 137 136 


3 30 


_ 


5 4 


_ 


5 2 


14 28 71 107 129 13 3 


360 


- 


5 3 


- 


2 4 


11 49 84 110 12 5 128 


Table 75. 


Computed 


values of s 


ecular change in vertical component (Z) of magnetic field intensity for 1942.5 










at height 100 km expressed in units of 10"" CGS Der year 


Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


no 


30 




20 1 




39 5 


564 658 633 476 218 - 46 - 1«2 


60 




24 9 




49 1 


69 5 823 851 75 1 501 137-216 


90 




24 4 




4 6 3 


5 91 5R1 451 239- 45-402-7RO 


ISO 




18 6 




34 4 


414 352 199 39- 79-164-2 49 


150 




9 4 




16 6 


1R9 139 46 - 40 _ 95 - 131 - 167 


18 


- 


1 


- 


10 


37 - 107 - 203 - 286 - 325 - 323 - 296 


2 10 


- 


70 


- 


113 


- 124 - 135 - 15 4 - 163 - 140 - 8 6 - 17 


?! 4 


- 


101 


- 


15 9 


- 192 - 252 - 33 5 - 377 - 320 - 170 10 


2 70 


- 


9 4 


- 


15 4 


- 217 - 316 - 395 - 348 - 14O 137 328 


3 


- 


4 9 


- 


90 


- 158 - 288 - 426 - 4R2 - 425 - 329 - 308 


3 30 




2 4 




3 1 


28 - 209 - 485 - 756 - 922 - 959 - 911 


3 60 




115 




212 


255 193 18 - 218 - 446 - 597 - 627 




Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 




100 




110 


120 


130 


140 


150 


160 


170 


























30 


_ 


8 1 




25 8 


697 1020 1062 824 476 248 


60 


- 


38 


- 


25 


104 458 5 8 1 422 152 4R 


90 


- 


10 4 8 


- 


107 8 


- 850 - 511 - 263 - 203 - 227 - 114 


12 


- 


33 4 


- 


38 7 


- 388 - 368 - 375 - 409 - 378 - 159 


15 


- 


19 8 


- 


20 4 


- 184 - 169 - 192 - 235 - 214 - 46 


1 80 


- 


24 9 


- 


17 2 


53 ^4 194 233 2 14 201 


?! 1 




6 3 




17 9 


363 604 820 986 768 5 01 


2 4 




17 3 




341 


585 926 1256 1382 1193 738 


2 7 




35 8 




320 


404 710 1127 139 5 1282 R27 


3 


- 


39 


- 


45 9 


-336 5 5 592 1002 1073 76 5 


33 


- 


82 6 


- 


69 2 


-448- 67 37 5 717 802 614 


3 60 


- 


513 


- 


25 9 


88 439 6R4 745 633 436 



59 



Table 76. 


Computed values of 


secular change 


in vert 


cal component. (Z) of magnetic field intensity for 1942.5 






at hei 


ght 


300 km 


exp 


ressed 


in units of 10 _ 


8 CGS oer year 






Geographic 
east 










Geographic colatitude in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


1 R 7 


35 1 




4 9 4 




5 6 9 


54 4 




40 8 




18 9 


3 2 


- 14 5 


60 


22 9 


4 3 6 




6 10 




717 


73 5 




64 2 




42 3 


111 


- 18 3 


OO 


22 3 


40 9 




5 1 8 




511 


39 9 




212 


- 


3 9 


- 35 


- 67 


ISO 


17 2 


30 2 




3 5 8 




30 6 


17 7 




3 7 


- 


7 2 


- 15 5 


- P 3 6 


1 5 


9 2 


14 7 




16 2 




116 


3 5 


- 


4 


- 


9 1 


- 12 5 


- 15 6 


1 R 


9 


4 


- 


3 2 


- 


9 4 


- 17 6 


- 


24 6 


- 


28 2 


- 28 1 


- 25 8 


2 10 


5 1 


6 


- 


114 


- 


12 9 


- 14 6 


- 


15 3 


- 


13 2 


8 3 


19 


?40 


p 


- 13 9 


- 


17 6 


- 


23 


- 29 5 


- 


32 4 


- 


27 1 


- 14 


1 6 


2 70 


7 4 


- 13 8 


- 


19 9 


- 


2 R 5 


- 34 6 


- 


3O4 


- 


130 


100 


26 3 


3 


3 6 


R 3 


- 


1 5 2 


- 


26 6 


- 3R 3 


- 


4 3 2 


- 


3R 8 


- 311 


- 28 9 


3 3 


P. 9 


P 4 


- 


3 5 


- 


19 5 


- 4 3 1 


- 


6 6 1 


- 


80 5 


- 84 3 


- 80 5 


3 60 


111 


1 P. 7 




? 1 7 




15 8 


5 


- 


19 9 


- 


39 5 


- 52 4 


- 54 8 




Geographic 
east 










Geograohi 


c colatitude in 


degrees 








longitude 


100 


110 




120 




130 


140 




150 




160 


170 




in degrees 




























3 


5 9 


22 3 




5 8 8 




85 8 


9 




71 5 




4 4 


25 8 




60 


- 31 fi 


- 211 




Rl 




37 4 


4 R 3 




36 6 




16 1 


8 8 




q 


- R 9 3 


- 9 16 


- 


72 7 


- 


4 4 5 


- 23 1 


- 


16 4 


- 


16 2 


4 9 




1 2 


- 311 


- 35 7 


- 


35 7 


- 


33 6 


- 33 1 


- 


34 


- 


29 


8 8 




1 5 


- 1 R ? 


- 1 R 6 


- 


16 9 


- 


15 4 


- 16 5 


- 


18 5 


- 


15 


5 




IfiO 


- 2 1 5 


- 14 4 


- 


3 9 




8 1 


17 8 




219 




21 3 


21 3 




3 10 


5 R 


16 7 




33 




53 7 


71 9 




7 8 3 




6 8 


46 4 




34 


16 3 


31 R 




53 3 




82 


109 2 




119 7 




103 5 


66 2 




3 7 


30 1 


P9 




37 6 




63 8 


9 8 2 




119 5 




110 9 


7 3 7 




10O 


- 34 4 


- 3 R P 


- 


26 1 




7 4 


52 5 




87 4 




9 3 5 


68 6 




3 3 


- 72 8 


- 60 1 


- 


37 9 


- 


4 4 


33 7 




6 3 




71 2 


56 2 




3 60 


- 4 4 6 


- 22 3 




7 8 




38 3 


59 7 




65 9 




57 4 


416 




Table 77. 


Computed 


values of s 


ecular char 


lge 


in vertical component 


(Z) of m 
6 CGS p 


agn 


etic field intensity for 1942.5 






at he 


ight 


500 km 


expressed 


in units of 10- 


er year 






Geographic 
east 










Geographic colatitude in 


degrees 








longitude 


10 


20 




30 




40 


50 




60 




70 


80 


90 


in degrees 




























3 


17 3 


31 3 




43 3 




49 5 


47 




35 1 




16 4 


2 2 


- 115 


60 


211 


3R 8 




53 7 




62 7 


6 3 7 




55 1 




35 8 


9 2 


- 15 6 


90 


20 4 


36 2 




4 5 6 




45 


35 3 




18 8 


- 


3 4 


- 30 5 


- 57 8 


13 


15 9 


26 6 




31 2 




26 7 


15 3 




3 4 


- 


6 6 


- 147 


- 22 2 


15 


R 8 


13 1 




13 9 




9 8 


2 7 


- 


3 9 


- 


86 


- 118 


- 146 


1 BO 


1 6 


1 


- 


2 9 


- 


8 3 


- 15 4 


- 


21 4 


- 


24 5 


- 24 6 


- 22 5 


2 10 


3 7 


R 3 


- 


10 4 


- 


121 


- 13 8 


- 


14 3 


- 


12 3 


7 9 


19 


3 4 


6 3 


- 12 3 


- 


16 2 


- 


209 


-•262 


- 


28 1 


- 


23 1 


- 117 


2 1 


3 70 


5 9 


- 12 3 


- 


1 R 4 


- 


25 7 


- 30 6 


- 


26 7 


- 


12 


71 


212 


3 


2 6 


7 6 


- 


14 4 


- 


24 6 


- 34 6 


- 


38 8 


- 


35 4 


- 29 2 


- 27 


3 3 


3 2 


1 9 


- 


4 


- 


1 R 1 


- 3 8 4 


- 


58 1 


- 


707 


- 74 3 


- 713 


3 60 


105 


16 6 




18 6 




130 


4 


- 


1 R 2 


- 


35 2 


- 4 6 3 


- 4 81 




Geographic 
east 










Geographi 


c colatitude 


> in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 

1 


150 


160 


170 




30 


4 3 


19 3 




49 9 




72 7 


76 8 




624 




4O4 


25 9 




60 


- 26 8 


- 17 9 




6 2 




30 7 


40 4 




31 9 




16 4 


115 




90 


- 76 6 


- 78 4 


- 


62 6 


- 


38 9 


- 20 3 


- 


13 3 


- 


112 


2 




12 


- 29 


- 32 9 


- 


32 9 


- 


307 


- 29 2 


- 


28 3 


- 


22 1 


3 6 




150 


- 16 6 


- 16 9 


- 


15 5 


- 


140 


- 14 2 


- 


146 


- 


100 


4 2 




1 BO 


- 18 6 


- 12 1 


- 


2 8 




77 


16 3 




20 5 




20 9 


21 8 




210 


5 3 


15 5 




301 




47 9 


63 4 




6 8 8 




60 5 


42 9 




24 


15 3 


29 4 




4 8 5 




72 9 


95 5 




104 




90 4 


59 5 




2 70 


25 5 


261 




34 8 




57 4 


86 




1037 




96 5 


65 9 




3 


- 30 4 


- 32 


- 


20 4 




8 7 


46 9 




76 3 




81 9 


617 




330 


- 64 3 


- 52 4 


- 


32 2 


- 


2 6 


30 5 




55 9 




63 5 


515 




3 60 


- 38 9 


- 19 4 




6 9 




33 4 


52 3 




5 8 4 




52 1 


39 3 





60 







at hei 


ght 1000 ki 


n expresse< 


i in 


units of 


10-b CGS 


3er year 








Geographic 
east 








Geographi 


c colatitude 


in degrees 






longitude 


10 


20 


30 




40 




50 


60 


70 


80 


90 


in degrees 
























30 


14 


2 3 6 


316 




35 4 




3 3 1 


24 5 


1 1 6 - 8 


6 8 


60 


16 8 


2 9 2 


39 6 




4 5 5 




45 5 


3 8 4 


24 3 S 9 


- 10 7 


9 


16 2 


27 1 


33 6 




33 2 




26 3 


13 9 


2 5 - 22 


- 40 8 


12 


12 8 


198 


?2 6 




19 4 




117 


2 6 


5 4 - 12 4 


- 18 7 


15 


7 6 


9 9 


9 R 




6 5 




1 3 


3 6 


7 5 - 10 1 


- 12 2 


IPO 


2 3 


3 


2 2 


- 


6 3 


- 


113 


- 15 5 


- 178 - 179 


- 163 


?! 1 


1 7 


5 9 


fl 4 


- 


10 3 


- 


117 


- 119 


- 10 2 - 6 7 


17 


2 4 


3 7 


2 


- 12 9 


- 


1 « 6 


- 


19 7 


- 20 1 


- 15 9 - 7 6 


2 6 


2 7 


3 6 


O (S 


- 14 8 


- 


PO 


- 


23 


- 19 9 


- 10 1 2 6 


12 6 


TOO 


12 


fi 3 


- 12 4 


- 


■p l 


- 


27 1 


- 30 ?. 


- ? R 4 - 24 5 


- 22 4 


3 3 


3 2 


1 o 


4 5 


- 


150 


- 


29 2 


- 4 3 


- 5 2 2 - 5 5 3 


- 53 4 


3 60 


R 6 


12 3 


12 8 




R 


- 


1 8 


- 1 A f, 


- 26 5 - 343 


- 35 3 




Geographic 
east 








Geographi 


c colatitude 


in degrees 






longitude 


100 


110 


120 




130 




140 


150 


lfiO 


170 




in degrees 
























3 


1 R 


13 7 


33 8 




4 9 1 




5 3 


4 5 2 


32 6 24 3 




60 


- 1 R 


- 12 2 


3 3 




19 3 




26 8 


23 3 


15 6 14 4 




90 


- 53 3 


- 5 4 4 


- 4 4 


- 


2 R 1 


- 


14 8 


7 8 


3 4 6 2 




12 


- 23 9 


- 26 7 


- 26 5 


- 


24 2 


- 


215 


- 18 1 


-10 9 3 8 




15 


- 13fi 


- 13 6 


- 12 4 


- 


10 9 


- 


9 8 


7 9 


2 3 9 1 




3 R 


- 13 1 


R 


10 




6 7 




13 4 


17 3 


19 1 210 




2 10 


4 5 


12 8 


23 9 




36 5 




471 


510 


4 60 352 




2 4 


130 


24 3 


3 R 4 




55 1 




6 9 8 


74 9 


66 46 3 




2 7 


174 


20 5 


28 5 




4 4 3 




6 3 2 


74 5 


69 9 50 5 




3 


- 22 8 


- 210 


- 10 9 




9 9 




3 5 9 


5 5 8 


60 3 47 9 




3 3 


- 4 7 8 


- 37 8 


- 218 




1 




23 9 


42 3 


4 R 4 413 




3 60 


- 2R 3 


- 13 9 


5 2 




24 4 




3 8 4 


4 3 9 


410 333 





Table 79. Computed values of secular change in vertical component (Z) of magnetic field intensity for 1942.5 
at height 5000 km expressed in units of 10-6 CGS per year 



expr 



per yes 



Geographic 
east 










G 


sographic colatitude in 


degrees 




longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


22 




3 3 


40 




41 




36 




2 5 11 - 


3 


60 


2 8 




44 


5 5 




60 




56 




43 2 5 5 - 


10 


90 


27 




41 


48 




47 




37 




18 - 4 - 30 - 


51 


120 


2 2 




29 


30 




2 5 




14 


- 


- 17 - 33 - 


45 


150 


1 3 




13 


10 




3 


- 


5 


- 


14- 22- 29- 


3 2 


180 


5 


— 





7 


— 


14 


- 


21 


- 


26- 29- 2 8- 


23 


210 


1 


- 


1 2 


20 


- 


2 6 


- 


2 e 


m 


27- 22- 13- 





24 


6 


- 


19 


2 9 


- 


3 5 


- 


36 


- 


32 - 2 1 - 6 


13 


270 


7 


- 


2 2 


35 


- 


4 4 


- 


46 


- 


41 - 30 - 14 


4 


300 


4 


- 


19 


3 5 


- 


49 


- 


60 


- 


65- 65- 59- 


50 


330 


3 


- 


7 


2 2 


- 


39 


- 


5 9 


- 


76- 88- 92- 


87 


3 60 


1 3 




13 


7 


- 


2 


- 


17 


- 


34- 48- 55 - 


5 3 




Geographic 
east 










G< 


?ograph 


lc colatitud 


e in 


degrees 




longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


1 




15 


34 




5 2 




6 4 




6 9 71 7 3 




60 


17 


- 


13 


1 




1 5 




29 




40 49 6 1 




90 


64 


— 


6 5 


5 5 


- 


36 


— 


15 




6 2 8 52 




120 


54 


- 


56 


5 2 


- 


41 


- 


2 5 


-. 


3 2 2 50 




150 


33 


- 


3 1 


2 5 


— 


16 


- 


3 




13 34 56 




1 80 


16 


- 


4 


8 




2 3 




37 




50 6 1 70 




210 


1 5 




3 4 


5 3 




71 




85 




9 2 9 1 85 




240 


34 




57 


80 




100 




11 4 




119 112 96 




270 


2 2 




42 


6 4 




87 




107 




117 115 100 




300 


36 


— 


16 


10 




42 




7 3 




96 10 5 9 8 




330 


7 2 


- 


48 


17 




1 8 




53 




7 9 93 9 2 




3 60 


40 


- 


19 


8 




36 




60 




7 6 83 8 3 





61 



Table 80. Computed values of secular change in vertical component (Z) of magnetic field intensity for 1932.5 
at depth 1000 km expressed in units of 10-6 CGS per year 



Geographic 
east 




Geographic colatitude 


in degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


- 446 142 863 


142 8 


154 


10 8 7 


271 


- 46 4 


- 66 6 


60 


- 297 344 1041 


167 7 


210 2 


2 12 3 


1619 


721 


- 114 


90 


-27 1 269 691 


919 


95 6 


74 9 


16 


- 85 6 


-20 2 8 


12 


-361 29 299 


4 2 3 


4 3 9 


36 6 


18 8 


7 3 


- 27 7 


15 


- 528 - 326 - 142 


9 6 


33 5 


35 


2 2 


- 62 7 


-1001 


18 


- 713 - 678 - 684 


- 62 9 


- 4 8 


- 38 1 


- 517 


- 886 


-1213 


2 10 


- 872 - 854 - 79 5 


- 713 


- 600 


- 47 6 


- 38 7 


- 35 4 


- 32 9 


24 


-1016 -1067 -1057 


-10 9 4 


-1147 


-107 9 


- 79 9 


- 38 8 


3 5 


2 7 


-112 6 -1380 -1642 


-185 6 


-172 8 


- 97 2 


31 7 


155 


2 02 3 


3 


-1117 -139 4 -1643 


-1811 


- 1 697 


-112 2 


- 180 


670 


882 


3 3 


- 949 - 946 - 838 


- 88 8 


-130 8 


-2018 


-265 9 


- 2 89 


- 2 67 2 


3 60 


-689-32 4 211 


56 


38 


- 34 8 


-126 2 


-1 87 5 


-193 1 




Geographic 
east 




Geographic colatitude 


in degrees 






longitude 
in degrees 


100 


110 


120 


130 


14Q 


150 


160 


170 




3 


- 130 970 2173 


2 970 


307 3 


2 541 


1714 


1017 




60 


- 32 2 36 5 1630 


270 1 


2 87 9 


207 5 


918 


30 5 




90 


-2780 -262 3 -1601 


- 37 2 


26 3 


3 8 


- 501 


- 4 3 2 




120 


-22 5 120 500 


4 86 


- 131 


-104 3 


-1 51 1 


- 90 3 




15 


-740 77 840 


86 7 


1 2 


-1113 


-1571 


- 84 1 




180 


-1162 - 660 - 18 


29 8 


86 


- 39 3 


- 60 1 


- 18 3 




2 10 


- 200 122 625 


115 8 


150 7 


152 6 


124 3 


87 8 




2 4 


166 380 905 


184 7 


2 89 5 


34 4 9 


3073 


192 3 




2 70 


1517 598 238 


10 2 1 


2 59 2 


3866 


387 1 


2 53 4 




3 


28 8 - 637 -1036 


- 30 9 


1343 


2 96 3 


349 6 


2 56 2 




3 3 


-2257 -1877 -1461 


- 70 4 


52 9 


187 9 


260 9 


217 2 




3 60 


-152 5 - 933 - 32 7 


31 6 


104 7 


1718 


199 3 


162 2 




Table 81. Computed values of secular change 


in magnetic potential (V), main field, for 1912.5 




express 


ed in units 


of 103 CGS 


per year 








Geographic 
east 




Geographi 


c colatitude 


in degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


12 2 90 4 6 





3 


3 6 


2 1 





6 


60 


116 76 16 


5 8 


- 13 2 


- 18 2 


- 200 


- 19 5 


- 19 


90 


116 7 9 2 9 


2 6 


7 3 


9 3 


8 2 


51 


20 


12 


12 2 9 7 6 9 


4 8 


3 9 


4 1 


4 9 


54 


50 


15 


132 121 112 


10 5 


100 


9 5 


90 


85 


7 5 


180 


144 147 152 


15 6 


15 2 


14 1 


12 9 


119 


10 9 


210 


155 165 171 


167 


14 9 


12 2 


92 


6 3 


3 4 


2 4 


163 180 184 


167 


12 9 


80 


3 5 


3 


19 


2 70 


167 193 211 


19 9 


14 3 


4 8 


5 7 


- 13 4 


- 163 


3 


162 190 218 


22 8 


19 6 


119 


1 9 


5 8 


84 


3 3 


150 160 178 


20 5 


23 5 


25 8 


267 


264 


25 3 


3 60 


135 12 106 


10 5 


12 6 


166 


211 


246 


25 7 




Geographic 
east 




Geographi 


c colatitude 


in degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


14- 63-12 6 


- 18 4 


- 22 3 


- 236 


- 22 7 


- 205 




60 


- 20 4 - 239 - 281 


- 305 


- 29 7 


- 26 1 


- 217 


- 18 6 




90 


13- 42- 96 


- 15 1 


- 18 2 


- 18 2 


- 166 


- 160 




120 


3 3 3 - 3 5 


71 


9 4 


- 103 


- 112 


- 136 




15 


54 2 1 - 16 


47 


6 4 


7 2 


8 9 


- 12 8 




180 


8 9 5 3 5 


40 


71 


90 


- 10 9 


- 140 




210 


2- 47- 95 


- 13 5 


- 160 


- 167 


- 167 


- 170 




24 


46- 86-139 


- 19 5 


- 234 


- 247 


- 23 2 


- 20 4 




2 70 


- 150 - 129 - 134 


- 176 


- 23 2 


- 270 


- 267 


- 228 




30 


61- 25- 22 


7 3 


- 157 


- 23 2 


- 260 


- 23 5 




330 


237 204 141 


4 2 


7 4 


- 17 7 


- 23 3 


- 22 9 




3 60 


240 19 3 117 


1 8 


86 


- 173 


- 219 


- 218 





62 



Table 82. Computed values of secular change in magnetic potential (V), main field, for 1922.5 
expressed in units of 10** CGS per year 



Geographic 
east 




Geograph 


ic colatitude in 


degrees 






longitude 


10 


20 


30 




40 




50 




60 


70 


80 


90 


in degrees 


























30 


12 6 8 6 4 3 




3 


_ 


2 3 


— 


3 1 


19 


'1 


4 


60 


117 6 9 13 


- 


4 8 


- 


10 4 


- 


14 1 


- 14 6 


- 12 6 


- 10 5 


90 


118 75 2 7 


- 


2 1 


- 


60 


- 


80 


6 9 


3 4 


6 


120 


12 9 9 7 6 5 




37 




2 




1 5 


1 9 


2 8 


3 4 


15 


145 129 109 




90 




74 




6 4 


5 9 


5 9 


5 5 


18 


163 161 154 




14 3 




12 8 




111 


9 6 


8 1 


6 6 


210 


178 185 179 




161 




13 5 




10 5 


7 5 


4 4 


1 3 


24 


189 206 204 




18 3 




14 8 




10 4 


5 6 


7 


3 7 


2 70 


19 2 221 237 




23 1 




19 5 




12 6 


3 9 


4 2 


9 8 


3 


184 PI 4 242 




25 8 




24 4 




19 4 


121 


5 2 


1 2 


3 3 


166 178 197 




22 4 




25 5 




27 8 


28 5 


27 8 


26 1 


3 60 


144 126 113 




112 




12 9 




159 


19 3 


21 8 


22 5 




Geographic 
east 




Geographi 


c colatitude in 


degree; 








longitude 
in degrees 


100 


110 


120 




130 




140 




150 


160 


170 




























30 


20- 79-156 


_ 


22 6 


_ 


27 


_ 


280 


- 26 7 


- 25 




60 


- 109 - 150 - 214 


- 


26 9 


- 


29 


- 


27 4 


- 24 3 


- 22 6 




90 


2 5 4 - 5 2 


- 


117 


- 


16 4 


- 


18 2 


- 18 4 


- 19 9 




12 


2 9 7 - 2 7 


- 


6 3 


- 


9 2 


- 


113 


- 137 


- 17 9 




15 


41 1 2 - 2 4 


_ 


57 


- 


80 


- 


10 


- 130 


- 17 9 




18 


4 5 1 4 - 2 5 


- 


6 7 


- 


10 3 


- 


13 3 


- 16 3 


- 19 9 




2 10 


19- 56- 97 


- 


14 1 


- 


18 2 


- 


21 2 


- 22 9 


- 23 5 




2 4 


80-122 - 169 


- 


22 


- 


26 8 


- 


29 7 


- 29 6 


- 270 




2 7 


- 125 - 138 - 164 


- 


21 4 


- 


27 7 


- 


32 3 


- 32 8 


- 29 2 




3 


4 3-25 


- 


9 5 


- 


19 2 


- 


27 6 


- 313 


- 29 4 




3 3 


235 193 122 




1 6 


- 


10 7 


- 


217 


- 2 8 


- 28 3 




3 60 


20 5 15 2 69 


- 


3 4 


- 


13 9 


- 


22 2 


- 26 6 


- 267 





Table 83. Computed values of secular change in magnetic potential (V), main field, for 1932.5 

expressed in units of 10^ CGS per year 



Geographic 
east 








Geographic colatitude 


in degrees 








longitude 


10 


20 


30 




40 




50 




60 


70 


80 


90 


in degrees 


























3 


6 7 


2 1 


2 4 


_ 


5 7 


_ 


6 5 


_ 


48 


17 


7 


6 


60 


5 2 


6 


62 


- 


10 6 


- 


12 8 


- 


12 4 


9 6 


57 


2 8 


90 


5 2 





4 2 


- 


6 9 


- 


7 4 


- 


5 5 


14 


3 8 


8 6 


120 


6 5 


2 8 





- 


1 4 


- 


17 


- 


7 


1 2 


3 2 


4 5 


150 


8 5 


67 


5 1 




3 9 




3 1 




3 5 


4 8 


6 3 


66 


180 


10 8 


107 


10 4 




9 8 




9 2 




90 


92 


9 5 


90 


2 10 


12 9 


141 


14 3 




137 




12 5 




10 8 


8 9 


66 


3 8 


2 4 


14 5 


16 9 


17 8 




174 




15 7 




12 5 


8 3 


3 5 


12 


2 70 


15 1 


18 6 


207 




207 




17 9 




12 


4 2 


3 2 


8 3 


3 


14 4 


17 8 


20 5 




21 6 




206 




17 2 


12 2 


7 2 


3 8 


3 3 


12 3 


13 9 


15 4 




174 




20 2 




23 3 


25 5 


25 8 


23 9 


3 60 


9 4 


7 7 


62 




5 9 




79 




117 


15 8 


181 


174 




Geographic 
east 








Geographii 


: co 


latitude 


in degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


2 9 


9 2 


- 16 5 


_ 


22 3 


_ 


25 5 


_ 


25 8 


- 24 2 


- 22 4 




60 


3 1 


70 


- 132 


- 


190 


- 


218 


- 


21 5 


- 19 7 


- 192 




90 


10 6 


86 


3 1 


- 


3 3 


- 


8 3 


- 


110 


- 12 7 


- 15 8 




12 


42 


2 2 


5 


- 


2 8 


- 


40 


- 


5 2 


80 


- 137 




150 


46 


9 


2 8 


- 


48 


- 


5 2 


- 


5 5 


81 


- 140 




180 


66 


2 5 


2 2 


- 


6 3 


- 


90 


- 


10 8 


- 132 


- 16 9 




210 


2 


4 3 


96 


- 


147 


- 


187 


- 


21 


- 216 


- 214 




24 


5 7 


- 104 


- 15 9 


- 


219 


- 


27 3 


- 


30 1 


- 29 3 


- 25 6 




2 70 


- 105 


- 116 


- 148 


- 


196 


- 


26 5 


- 


31 7 


- 32 2 


- 280 




3 


2 3 


1 1 


2 1 


- 


91 


- 


184 


- 


267 


- 30 4 


- 28 1 




3 3 


200 


143 


6 9 


- 


2 3 


- 


12 7 


- 


22 


- 27 2 


- 26 8 




3 60 


134 


70 


8 


- 


90 


- 


16 8 


- 


22 7 


- 25 6 


- 24 9 





63 



Table 84. Computed values of secular change in magnetic potential (V), main field, for 1942.5 

expressed in units of 10^ CGS per year 



Geographic 
east 








Geograph 


lc colatitude in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


- 4 6 


78 


- 10 3 


_ 


114 


— 


105 


_ 


7 6 


3 5 


4 


2 2 


60 


57 


- 10 


- 13 5 


- 


15 3 


- 


15 1 


- 


12 6 


78 


17 


3 5 


90 


5 5 


9 3 


- 115 


- 


114 


- 


89 


_ 


4 5 


1 2 


7 8 


14 


120 


4 3 


67 


7 5 


- 


6 3 


- 


3 5 


_ 


2 


2 9 


5 6 


80 


15 


2 4 


3 1 


2 8 


- 


1 5 




3 




2 2 


3 7 


4 8 


5 5 


180 


5 


3 


1 4 




3 




4 6 




60 


6 7 


6 5 


57 


2 10 


10 


2 7 


3 9 




47 




5 1 




50 


4 2 


2 5 


2 


2 4 


1 8 


4 1 


5 7 




70 




7 8 




76 


5 7 


2 3 


17 


2 70 


19 


4 5 


6 6 




8 6 




9 5 




8 4 


4 9 


4 


3 6 


3 


1 1 


3 4 


60 




90 




116 




12 7 


12 1 


105 


91 


3 30 


5 


7 


3 1 




71 




12 1 




167 


19 8 


207 


196 


3 60 


2 6 


3 5 


3 3 


- 


1 3 




2 1 




6 4 


10 4 


12 7 


12 8 




Geographic 
east 








Geograph 


ic colatitude in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


5 


4 5 


- Ill 


„ 


16 4 


_ 


183 


_ 


167 


- 136 


- 117 




60 


5 8 


40 


9 


_ 


6 3 


- 


9 3 


- 


92 


79 


8 4 




90 


180 


18 3 


14 9 




9 4 




4 4 




1 1 


15 


5 7 




120 


9 8 


10 6 


101 




8 6 




67 




4 4 


7 


4 9 




150 


5 9 


5 6 


4 7 




3 5 




2 2 




5 


2 3 


6 8 




180 


4 3 


2 1 


— 6 


- 


3 8 


- 


66 


- 


8 5 


9 7 


- 10 8 




210 


2 5 


60 


- 10 2 


_ 


14 8 


- 


186 


- 


20 1 


- 18 8 


- 15 5 




24 


60 


- 10 5 


- 15 8 


- 


216 


- 


26 5 


•- 


28 2 


- 25 4 


- 19 2 




2 70 


6 2 


8 4 


- 12 


- 


17 8 


- 


24 2 


- 


27 9 


- 26 6 


- 206 




3 


8 2 


6 3 


1 8 


- 


5 8 


- 


14 8 


- 


216 


- 23 4 


- 19 7 




3 30 


17 


12 8 


6 4 


- 


1 6 


- 


10 2 


- 


16 8 


- 19 4 


- 17 5 




3 60 


10 


4 8 


20 


- 


90 


- 


14 3 


- 


16 9 


- 167 


- 14 8 





Table 85. Computed values of secular change in magnetic potential (V), residual field, for 1942.5 

expressed in units of 10^ CGS per year 



Geographic 
east 


Geographic colatitude in degrees 


longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


- 1 4 9 


- 1 3 2 


- 1 4 4 3 


-13 5 1 


- 1 4 


- 56 


7 55 9 


9 6 8 


60 


- 1 1 4 7 


-15 4 


- 1 6 9 8 


- 1 6 5 9 


- 1 3 7 5 


- 8 8 5 


- 2 5 8 3 9 3 


92 1 


90 


-113 7 


- 1 4 8 7 


- 1 6 8 1 


- 1 6 5 6 


-14 2 


- 95 2 


- 36 4 26 7 


8 4 


1 2 


- 1 2 2 


- 1 2 7 3 


- 1 3 9 9 


- 1 3 4 9 


- 1 12 4 


- 75 8 


- 29 8 19 4 


62 7 


15 


- 83 3 


- 92 


- 92 8 


- 82 


- 613 


- 35 2 


7 3 20 5 


4 5 5 


18 


- 62 1 


- 52 3 


- 39 4 


- 210 


5 


16 


2 5 5 3 


33 2 


210 


- 4 4 2 


- 18 9 


5 9 


316 


53 4 


63 8 


59 2 4 4 3 


28 5 


2 4 


- 34 5 


Fj 


313 


62 2 


86 7 


96 


8 5 5 6 7 


33 2 


2 7 


- 35 4 


2 1 


29 9 


62 4 


90 2 


10 3 6 


9 6 9 74 


45 7 


3 


- 4 6 9 


- 23 3 


2 1 


32 3 


63 1 


85 1 


912 82 2 


6 4 3. 


3 3 


- 65 8 


- 5 8 5 


- 4 4 8 


- 20 2 


12 5 


45 1 


6 9 5 8 2 


82 1 


3 6 


- 87 


- 98 3 


- 9 8 4 


- 816 


- 4 8 8 


6 7 


3*0 7 19 


9 3 6 




Geographic 
east 








Geograph 


ic colatituc 


e in degree 


>s 




longitude 


100 


110 


120 


130 


140 


150 


160 


170 




in degrees 




















3 


110 7 


915 


4 6 1 


6 4 


- 4 4 9 


- 59 3 


- 568 - 549 




60 


117 1 


10 8 


73 7 


34 7 


10 1 


3 5 


1-206 




90 


1 10 1 


10 9 5 


86 6 


60 2 


4 6 1 


4 3 7 


3 5 2 - i 




12 


89 1 


9 3 


79 3 


616 


52 


4 9 6 


38 6 10 




15 


62 1 


65 3 


55 4 


39 5 


26 9 


19 7 


9 4 - 17 5 




18 


35 9 


33 6 


21 3 


1 


- 22 4 


- 37 7 


- 44 5 - 508 




210 


16 8 


5 5 


- 14 2 


- 4 6 5 


- 82 9 


- 1 7 5 


-108R - 099 




24 


10 6 


- 10 5 


- 4 14 


- 87 3 


-137 9 


-170 5 


- 1 6 5 9 - 1 2 4 3 




2 70 


18 8 


- 10 3 


- 52 4 


- 1 1 9 


- 1 7 2 2 


-.20 9 6 


-2004 -144 6 




3 


4 4 


6 8 


- 4 4 1 


-1111 


-177 


- 2 1 4 5 


-2032 -1456 




3 3 


67 9 


34 6 


- 20 2 


- 89 1 


- 1 5 1 8 


- 1 8 4 5 


-1739 -1270 




3 60 


9 3 2 


65 2 


12 3 


- 511 


- 10 3 8 


- 1 2 7 9 


-120 4 - 938 





64 



Table 86 


. Computed values of 


secular change in the vertical gradient of north 


component of magnetic field 




intensity ( 8X/ 3r), main field, for 1912.5 expressed in 


units of 10- 


14 CGS 


per year 




Geographic 
east 






Geographic colatitude in 


degrees 












longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


86 




215 318 29 1 


114 


_ 


137 


«, 


26 6 


_ 


230 


2 5 


60 


70 




22 6 440 556 


463 




21 1 


- 


8 3 


- 


186 


61 


90 


7 5 




206 344 368 


22 5 


- 


3 8 


- 


28 1 


- 


40 8 


- 29 2 


120 


8 3 




147 146 63 


4 1 


- 


11 4 


- 


119 


- 


3 6 


3 8 


150 


5 8 




6 1 4 2 1 


17 




2 6 




1 9 


- 


1 7 


3 2 


1 R 


4 


- 


50- 81- 38 


4 3 




79 




16 


- 


3 9 


3 2 


210 


47 


- 


8 3 - 5 8 3 2 


131 




15 4 




14 6 




10 8 


12 7 


24 


- 100 


- 


115- 21 141 


26 3 




27 4 




142 




2 5 


1 2 


2 70 


- 14 5 


- 


234 - 166 121 


514 




77 3 




71 6 




308 


- 16 


3 


- 117 


- 


24 3 - 264 - 37 


38 9 




74 4 




75 3 




38 3 


- 19 7 


3 3 


9 


- 


53 - 160 - 25 9 


- 26 5 


- 


14 7 









3 9 


2 7 


3 60 


76 




150 118- 44 


- 25 2 


- 


37 9 


- 


374 


- 


22 3 


5 1 




Geographic 
east 






Geographic colatitude 


in 


degrees 












longitude 
in degrees 


100 




110 


120 


130 


140 




150 




160 




170 






























3 


231 




409 431 309 


104 


_ 


9 1 


_ 


22 1 


_ 


24 2 




60 


18 2 




34 7 29 2 3 3 


- 27 7 


- 


45 4 


- 


40 3 


- 


16 4 




90 


6 




326 477 36 3 


6 6 


- 


19 3 


- 


21 




3 8 




120 


12 6 




203 217 127 


2 6 


- 


11 9 


- 


2 




25 4 




150 


13 5 




22 1 19 7 49 


- 11 3 


- 


13 9 




5 3 




35 




180 


89 




243 297 194 


2 7 


- 


5 1 




5 7 




26 9 




210 


202 




27 1 25 8 14 2 


11 


- 


115 


- 


101 




1 4 




24 


12 9 




306 417 37 2 


176 


- 


86 


- 


27 8 


- 


29 5 




2 70 


- 39 5 


- 


250 140 462 


45 9 




12 6 


- 


28 9 


- 


49 2 




3 


- 55 5 


- 


436 64 564 


69 4 




37 9 


- 


13 8 


- 


49 9 




330 


30 




169 456 738 


79 5 




52 9 




4 6 


- 


37 9 




3 60 


11 6 




293 489 645 


64 3 




42 7 




5 6 


- 


27 5 





Table 87. Computed values of secular change in the vertical gradient of north component of magnetic field 
intensity ( 3X/ 8r), main field, for 1922.5 expressed in units of 10-14 CGS per year 



Geographic 
east 




Geographi 


c colatitude in 


degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


21 


24 6 25 7 216 


97 


_ 


6 5 


- 216 


- 218 


3 7 


60 


20 8 


251 33 8 405 


35 




119 


- 15 8 


- 32 


- 212 


90 


18 


219 26 9 286 


20 8 




1 8 


- 25 8 


- 43 9 


- 38 9 


12 


13 4 


173 168 113 


36 


- 


4 5 


86 


- 10 


5 5 


15 


5 9 


103 121 112 


77 




2 7 


52 


7 9 


2 2 


180 


2 7 


13 3 8 6 3 


8 3 




6 8 


4 4 


9 


20 


2 10 


9 1 


3 7 9 13 3 


14 8 




14 8 


12 


10 9 


11 3 


24 


- 14 2 


45 70 156 


19 7 




19 9 


21 1 


202 


182 


2 70 


- 174 


-170-106 58 


306 




54 5 


59 9 


43 3 


13 


3 


- 12 6 


-198-218- 81 


210 




49 2 


58 3 


36 3 


19 


3 3 


9 


48 - 162 - 25 9 


- 25 6 


- 


136 


8 


6 4 


5 5 


3 60 


14 7 


15 3 76 - 6 3 


- 20 4 


- 


29 3 


- 276 


- 197 


65 




Geographic 
east 




Geographi 


c colatitude 


1 in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


25 5 


499 547 36 7 


6 7 


_ 


24 9 


- 264 


- 18 3 




60 


12 


44 7 52 2 27 5 


- 12 2 


- 


45 6 


- 349 


5 9 




90 


9 2 


288 510 431 


13 9 


- 


17 5 


93 


176 




120 


5 


165 205 129 


3 


- 


11 6 


93 


370 




150 


102 


209 20 5 8 3 


5 1 


- 


117 


139 


400 




180 


9 1 


181 220 176 


91 


- 


11 


123 


25 1 




210 


13 2 


16 9 20 9 22 3 


182 




2 1 


10 


37 




24 


17 3 


206 287 347 


28 9 




9 


- 19 7 


- 34 8 




2 70 


9 8 


78 174 44 5 


47 9 




12 8 


- 23 5 


- 517 




3 


- 27 7 


-192 197 610 


727 




37 5 


6 5 


- 47 5 




33 


57 


187 46 3 746 


82 3 




51 4 


11 5 


- 32 6 




3 60 


113 


331 54 5 667 


613 




307 


4 3 


- 22 5 





65 



Table 88. Computed values of secular change in the vertical gradient of north component of magnetic field 
intensity ( dX/ dr), main field, for 1932.5 expressed in units of 10-14 CGS per year 



Geographic 
east 




Geographic colatitude in 


degrees 












longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


26 7 


32 9 296 


14 8 


_ 


7 1 


_ 


260 


_ 


31 


_ 


17 8 


8 8 


60 


33 6 


36 6 334 


23 3 




6 4 


_ 


14 4 


- 


31 9 


- 


35 4 


- 18 7 


90 


310 


2 8 5 2 2 


84 


- 


5 7 


- 


22 3 


- 


38 7 


- 


4 6 5 


- 36 3 


ISO 


22 4 


18 9 12 3 


4 5 


- 


3 1 


_ 


10 2 


- 


15 


- 


14 2 


5 5 


150 


113 


10 1 97 


8 6 




2 8 


- 


81 


- 


17 6 


- 


15 5 


8 


1 fl 


7 


17 27 


4 2 




3 2 


- 


2 3 


_ 


9 2 


- 


9 8 


4 


2 1 


7 6 


15 2 4 


5 3 




72 




7 6 




7 2 




77 


114 


240 


- 15 6 


70 - 15 


2 9 




9 2 




17 4 




23 8 




24 5 


20 7 


2 70 


- 218 


- 16 3 - 9 5 


40 




26 2 




4 8 6 




56 5 




4 9 


10 


3 


- 19 9 


- 173 - 123 - 


1 5 




15 6 




32 7 




3 8 5 




26 1 


1 7 


3 3 


7 5 


3 9 - 5 6- 


14 3 


- 


24 1 


- 


260 


- 


16 2 




4 


150 


3 60 


110 


170 135 - 


2 1 


- 


23 


- 


36 


- 


32 2 


- 


13 


111 




Geographic 
east 




Geographic colatitude in 


degrees 












longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


36 3 


5 13 4 7 


26 2 


_ 


8 




197 


_ 


25 4 


_ 


17 3 




60 


12 6 


416 49 5 


30 2 


- 


4 4 


- 


28 2 


- 


26 2 




1 




90 


70 


28 2 4 8 7 


42 4 




17 1 


- 


3 4 




1 




28 9 




ISO 


7 7 


16 7 13 2 - 


1 7 


- 


13 3 


- 


9 4 




17 




50 9 




150 


217 


30 4 17 7 - 


7 4 


- 


22 8 


- 


13 6 




19 3 




52 4 




180 


17 2 


28 8 26 5 


12 3 


- 


10 


- 


1 3 




130 




30 7 




310 


18 6 


26 4 30 2 


26 3 




14 2 




1 2 


- 


7 9 


- 


7 1 




24 


lflfl 


24 6 36 2 


42 8 




31 9 




4 7 


- 


27 


- 


42 4 




2 70 


- 13 9 


- Ill 175 


4 8 8 




54 4 




24 5 


- 


23 1 


- 


56 9 




3 


- 16 


- 10 1 204 


56 3 




70 9 




4 7 3 


- 


1 9 


- 


4 9 




3 3 


23 4 


30 3 42 5 


5 8 9 




67 5 




51 7 




12 5 


- 


33 3 




3 60 


29 9 


4 1 44 5 


45 6 




410 




26 2 




1 5 


- 


23 7 




Table 81 


. Computed values of secular chang< 


3 in the vertical gr 


adi 


?nt of north 


component of magnetic field 




intensity 


( 8X/ 8r), main field, for 


1942.5 expressed 


in i 


jnits of 10" 


14 CGS 


per 


year 




Geographic 
east 




Geographic colatitude 


1 in 


degrees 












longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


230 


23 1 16 5 


4 2 


_ 


11 4 


— 


26 5 


_ 


33 9 


„ 


26 6 


3 2 


60 


29 6 


284 206 


9 4 


- 


4 4 


- 


21 7 


- 


39 1 


- 


46 7 


- 34 3 


90 


28 5 


22 9 7 3- 


9 5 


- 


218 


- 


30 8 


- 


39 9 


- 


46 7 


- 42 


120 


20 8 


15 2 1 - 


14 9 


- 


210 


- 


181 


- 


12 8 


- 


10 8 


- 113 


150 


90 


62 - 2 3- 


10 2 


- 


12 2 


- 


91 


- 


5 5 


- 


4 4 


4 3 


180 


2 4 


2 - 6 3- 


11 o 


- 


117 


- 


76 


- 


1 8 




2 4 


50 


210 


9 4 


3 4 - 14- 


2 2 


- 


2 1 




8 




5 4 




8 8 


10 3 


24 


- 12 2 


5 2 - 5 5- 


9 3 


- 


8 4 




10 




14 3 




22 6 


227 


2 70 


- 117 


73- 107 - 


12 8 


- 


3 4 




16 2 




32 7 




31 9 


149 


3 


7 8 


6 8-134- 


186 


- 


13 6 




4 




118 




97 


2 6 


3 3 


- 


2 9-154- 


30 


- 


35 8 


- 


280 


- 


119 




2 2 


9 5 


3 60 


114 


90 - 13- 


15 5 


- 


26 8 


- 


29 9 


- 


24 


- 


112 


56 




Geographic 
east 




Geographi 


c colatitude 


in 


degrees 












longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


280 


508 504 


24 7 


_ 


11 9 


_ 


37 5 


_ 


36 8 


- 


12 3 




60 


2 6 


32 2 47 7 


327 


- 


17 


- 


28 4 


- 


25 1 




7 5 




90 


- 197 


13 3 384 


39 8 




203 




10 




37 




310 




120 


9 2 


2 8 3 1 


3 3 


- 


8 




3 




15 8 




418 




150 


2 3 


17 3 8 


1 3 


- 


2 8 


- 


7 




12 4 




317 




180 


80 


12 9 17 3 


17 1 




106 




1 8 


„ 


2 1 




31 




2 10 


12 8 


19 3 27 7 


30 5 




20 1 


- 


2 5 


- 


25 7 


- 


33 4 




24 


207 


25 3 371 


4 40 




31 4 


- 


2 9 


- 


421 


- 


60 9 




2 70 


12 


18 25 2 


48 5 




46 4 




117 


- 


36 2 


- 


66 4 




3 


9 8 


2 8 33 4 


616 




637 




32 5 


- 


15 5 


- 


527 




33 


14 1 


23 8 40 3 


54 2 




52 3 




29 1 


- 


60 


- 


34 8 




3 60 


237 


39 45 8 


39 5 




20 8 


- 


2 4 


— 


19 5 


— 


23 1 





66 



Table 90. Computed values of secular change in the vertical gradient of east component of magnetic field 
intensity ( d Y/ dr), main field, for 1912.5 expressed in units of 10-14 CGS per year 



Geographic 
east 










Ge 


ographic colatitude 


in 


degrees 










longitude 


10 




20 


30 




40 




50 




60 


70 




80 


90 


in degrees 






























3 


2 




5 


5 1 


— 


16 9 


_ 


31 5 


.. 


44 2 


- 52 8 


_ 


58 1 


- 62 8 


60 


2 




2 


12 


- 


4 4 


- 


80 


- 


101 


87 


- 


2 8 


6 5 


90 


1 6 


- 





80 




219 




36 8 




47 


49 9 




47 3 


437 


120 


4 




3 3 


9 3 




150 




16 9 




13 3 


4 6 


- 


7 2 


- 19 1 


150 


4 9 




i o a 


15 




15 5 




119 




7 7 


71 




119 


19 5 


180 


7 8 




110 


13 3 




13 8 




12 1 




8 2 


2 5 


- 


4 2 


- 10 5 


210 


80 




6 9 


1 3 


- 


6 1 


- 


119 


- 


14 1 


- 13 2 


- 


11 3 


- 108 


24 


6 6 




107 


13 2 




12 




6 3 


- 


2 7 


- 114 


- 


15 8 


- 13 4 


2 70 


6 




5 9 


13 3 




16 6 




9 a 


_ 


7 7 


- 301 


- 


47 


- 49 9 


3 


8 6 


- 


14 


- 13 3 


- 


2 8 




17 




414 


630 




75 2 


75 6 


33 


- 117 


- 


23 6 


- 33 1 


- 


32 4 


- 


18 2 




5 5 


301 




4 6 1 


4 8 3 


3 60 


6 


— 


113 


- 20 9 


- 


32 2 


- 


412 


- 


44 5 


- 413 


- 


34 


- 27 




Geographic 
east 










Geographic colatitude 


in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


- 69 4 


- 


77 1 


- 814 


_ 


76 9 


.. 


59 9 


_ 


31 6 


1 3 




31 1 




60 


16 1 




22 8 


24 4 




21 9 




19 2 




20 9 


28 7 




410 




90 


43 2 




46 5 


513 




54 2 




53 4 




49 9 


461 




43 




120 


- 27 5 


- 


29 4 


- 23 5 


- 


10 6 




5 8 




20 4 


28 1 




26 2 




15 


25 7 




27 2 


23 5 




16 9 




106 




5 7 


1 4 


- 


4 2 




180 


- 14 6 


- 


15 9 


- 15 


- 


14 6 


- 


17 1 


- 


23 4 


- 315 


- 


37 4 




2 10 


- 12 7 


- 


17 


- 22 6 


- 


29 6 


- 


38 1 


- 


47 6 


- 55 9 


- 


586 




24 


53 




40 


7 9 




2 4 


- 


12 5 


- 


31 9 


- 483 


- 


55 6 




2 7 


- 36 9 


- 


14 3 


70 




17 7 




14 2 




1 


- 17 1 


- 


31 




3 


66 5 




5 3 6 


42 2 




34 7 




29 9 




23 8 


137 


- 


6 




3 30 


39 1 




25 9 


16 4 




14 3 




18 3 




23 1 


24 




19 5 




3 60 


- 24 3 


~ 


26 3 


- 30 2 


- 


308 


- 


24 5 


- 


94 


9 3 




26 3 




Table 91 


. Compute 


d v 


ilues of 


secular change in the vertical gradient of east component oi 


magnetic field 




intensil 


y OY/9r 


, main fiel 


i, for 1922.5 expressed in 


units of 10-14 CGS 


per 


year 




Geographic 
east 










Geographi 


c colatitude 


in 


degrees 










longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


7 2 


_ 


5 8 


90 


_ 


17 1 


_ 


27 8 


.» 


37 4' 


- 431 


m 


45 3 


- 467 


60 


1 8 




2 9 


2 2 


- 





- 


2 9 


- 


4 3 


19 




5 4 


16 7 


90 


8 3 




7 5 


103 




17 5 




25 9 




30 8 


29 4 




22 7 


15 4 


120 


13 7 




12 1 


118 




12 3 




12 7 




117 


8 4 




1 9 


6 4 


150 


17 2 




176 


17 9 




161 




12 3 




81 


5 4 




5 3 


72 


1 BO 


15 9 




14 9 


13 7 




12 5 




115 




96 


5 9 




7 


4 5 


2 10 


110 




8 4 


2 7 


- 


3 6 


- 


8 3 


- 


109 


- 118 


- 


12 5 


- 13 5 


2 4 


4 7 




9 8 


14 7 




17 6 




169 




12 


4 2 


- 


3 4 


8 3 


2 70 


5 5 




2 4 


114 




15 7 




11 3 


- 


1 8 


- 15 6 


- 


24 8 


- 23 7 


3 


- 180 


- 


17 7 


- 13 1 


- 


2 8 




12 6 




30 6 


47 




57 9 


613 


3 3 


- 23 9 


- 


30 4 


- 34 4 


- 


32 1 


- 


21 6 


- 


4 9 


12 7 




25 5 


29 9 


3 60 


- 18 3 


— 


21 9 


- 28 3 


- 


36 2 


- 


42 6 


- 


44 5 


- 407 


- 


334 


- 27 5 




Geographic 
east 










Geographi 


s colatitude 


in 


degrees 










longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


- 501 


_ 


55 1 


- 6 08 


_ 


59 2 


_ 


46 6 


— 


22 6 


80 




37 




60 


29 1 




38 5 


42 2 




40 9 




37 3 




35 8 


386 




45 1 




90 


12 6 




17 2 


27 4 




390 




47 1 




49 4 


46 4 




4 1 




120 


- 14 3 


- 


18 3 


- 160 


- 


74 




4 5 




15 


19 3 




15 3 




150 


9 5 




10 6 


9 5 




6 3 




1 5 


- 


4 5 


- 116 


- 


18 8 




180 


7 8 


- 


8 2 


7 5 


- 


7 9 


- 


14 2 


- 


261 


- 400 


- 


49 




2 10 


- 15 1 


- 


16 8 


- 196 


- 


25 


- 


34 2 


- 


466 


- 582 


- 


6 3 4 




24 


90 


- 


78 


87 


- 


12 9 


- 


23 3 


- 


36 4 


- 476 


- 


53 




2 70 


- 131 




3 


15 4 




19 5 




14 1 




2 6 


- 106 


_ 


22 5 




30 


581 




506 


44 6 




39 8 




36 1 




31 1 


22 4 




9 7 




3 30 


26 4 




19 5 


12 6 




110 




146 




206 


25 9 




27 4 




3 60 


- 26 9 


■* 


32 6 


- 40 5 


- 


44 


- 


37 1 


- 


18 5 


7 2 




31 8 





67 



Table 92 


. Computed values of secular change 


in the vertical gradient of east component of 


magnetic field 




intensity ( 3Y/ dr 


), main field, for 1932.5 expressed ir 


l units of 10 


-14 CGS 


per 


year 




Geographic 
east 












Geographic colatitude 


in 


degrees 












longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


- 23 1 


- 


22 6 


- 


22 6 


- 


24 9 


_ 


291 


_ 


336 


_ 


35 8 




350 


32 4 


60 


7 5 


— 


3 




1 4 




4 2 




5 1 




5 4 




8 1 




15 4 


27 2 


90 


77 




12 1 




16 7 




210 




23 4 




22 5 




17 7 




10 4 


3 8 


12 


18 5 




18 9 




16 4 




117 




6 2 




1 3 


_ 


3 1 


_ 


8 6 


- 16 5 


15 


23 5 




22 1 




20 4 




17 8 




14 9 




13 1 




13 2 




15 2 


17 6 


180 


22 9 




18 9 




16 4 




14 8 




12 7 




8 7 




2 4 


_ 


4 1 


86 
- 10 2 


2 10 


19 3 




14 8 




10 3 




72 




50 




2 7 


_ 


9 


_ 


5 6 


24 


13 3 




15 




16 3 




163 




13 3 




6 5 


_ 


2 6 


_ 


10 8 


- 14 5 


2 70 


1 6 




6 1 




87 




7 4 




1 4 


- 


7 6 


_ 


16 3 


_ 


20 6 


17 8 


3 


- 15 1 


- 


14 4 


- 


12 3 


- 


5 6 




7 9 




270 




46 3 




59 4 


6 19 


3 30 


- 29 


- 


32 8 


- 


34 4 


- 


31 1 


- 


22 


- 


8 6 




4 8 




13 7 


15 4 


3 60 


- 32 


~ 


35 3 


- 


37 6 


— 


38 9 


- 


39 2 


- 


37 6 


- 


33 9 


- 


29 3 


- 25 9 




Geographic 
east 












Geographic colatitude 


in 


degrees 












longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


- 306 


_ 


31 5 


_ 


33 9 


_ 


33 9 


_ 


26 3 


_ 


8 5 




17 6 




45 6 




60 


4 6 




50 9 




55 1 




53 2 




4 8 9 




46 7 




49 3 




55 3 




90 


10 




4 4 




13 8 




26 8 




39 7 




4 9 




519 




47 6 




12 


- 25 4 


- 


31 6 


- 


30 9 


- 


212 


- 


50 




10 9 




19 4 




163 




15 


18 8 




17 4 




13 3 




6 7 


- 


1 2 


- 


101 


- 


18 8 


- 


26 3 




180 


9 3 


- 


71 


- 


5 8 


- 


101 


- 


22 


- 


39 3 


- 


55 6 


- 


630 




210 


- 13 4 


- 


15 6 


- 


19 3 


- 


27 3 


- 


4 9 


- 


57 7 


- 


717 


- 


76 3 




2 4 


- 13 4 


- 


6 8 


- 


2 6 


- 


48 


- 


15 4 


- 


318 


- 


480 


- 


58 2 




2 70 


8 2 




50 




171 




23 5 




21 8 




12 


_ 


3 4 


- 


20 8 




3 


54 6 




42 7 




330 




29 2 




30 3 




30 9 




25 7 




13 




3 3 


105 




2 9 


- 


2 4 


- 


2 1 




4 4 




14 6 




24 3 




30 2 




3 60 


- 26 2 


- 


30 8 


- 


37 2 


- 


4 1 


- 


34 1 


- 


167 




92 




36 6 




Table 93 


. Compute 


d va 


lues of 


secular change 


in the vert 


ical gradient of east c< 


Dmponent of 


magnetic field 




intensity 


rOY/dr) 


, main field 


, for 1942.5 


ex] 


pressed 


in 


units of 10" 


14 CGS 


per 


year 




Geographic 
east 












Geographic colatitude 


in 


degrees 












longitude 
in degrees 


10 




20 




30 




40 




50 




60 




70 




80 


90 


































3 


- 17 5 


_ 


19 1 


_ 


21 2 


_ 


24 3 


_ 


27 7 


a. 


29 8 


_ 


29 1 


„ 


25 4 


- 200 


60 


5 6 


- 


40 


- 


1 




4 4 




78 




97 




12 




17 3 


270 


90 


80 




9 9 




14 




196 




24 2 




24 7 




19 5 




100 


2 


120 


19 1 




18 8 




160 




111 




5 


- 


1 5 


- 


8 5 


- 


15 9 


- 23 2 


15 


23 9 




23 5 




21 4 




18 3 




154 




13 5 




12 7 




12 3 


115 


180 


20 8 




17 6 




13 1 




8 4 




4 2 




10 


- 


1 9 


- 


51 


8 5 


210 


12 6 




8 7 




4 8 




1 7 


- 


1 


- 


14 


- 


2 5 


- 


4 


5 8 


24 


3 3 




3 4 




6 2 




10 4 




13 1 




118 




6 4 


- 


9 


6 6 


2 70 


5 9 


- 


3 8 


- 


1 8 


- 


15 


- 


3 8 


- 


7 5 


- 


10 


_ 


8 6 


2 2 


3 


- 14 5 


- 


10 9 


- 


6 3 




4 




10 2 




22 2 




340 




42 2 


44 6 


3 3 


- 210 


- 


19 3 


- 


17 7 


- 


15 8 


- 


12 8 


- 


8 5 


- 


41 


- 


1 4 


2 2 


3 60 


- 23 


~ 


24 7 


- 


28 3 


- 


32 8 


- 


35 6 


~ 


34 3 


- 


28 3 


- 


20 2 


- 146 




Geographic 
east 












Geographk 


; colatitude 


in 


degrees 












longitude 
in degrees 


100 




110 




120 




130 




140 




150 




160 




170 




































30 


- 15 3 


_ 


126 


.. 


11 6 


— 


9 5 


_ 


3 1 




9 3 




27 1 




45 9 




60 


39 9 




52 4 




60 6 




62 2 




58 4 




52 5 




47 7 




451 




90 


48 


- 


2 2 




76 




20 8 




322 




37 6 




35 5 




26 9 




12 


- 28 8 


- 


30 5 


- 


26 9 


„ 


187 


- 


90 


- 


2 1 


- 


1 4 


- 


76 




150 


96 




6 1 




8 


_ 


6 4 


- 


157 


- 


26 5 


- 


37 


= 


44 3 




180 


- 116 


_ 


14 6 


- 


186 


_ 


25 5 


- 


36 3 


- 


501 


- 


62 5 


- 


67 8 




210 


80 


- 


11 3 


- 


171 


- 


26 4 


- 


390 


- 


527 


- 


63 2 


- 


666 




24 


8 4 


- 


6 8 


- 


4 8 


- 


6 1 


- 


12 3 


- 


22 1 


- 


322 


- 


39 6 




2 70 


7 8 




187 




26 7 




29 9 




27 6 




209 




10 8 


- 


1 5 




3 


413 




35 1 




300 




28 6 




30 8 




336 




33 3 




27 7 




3 3D 


6 5 


- 


12 2 


- 


15 5 


- 


132 


- 


3 9 




107 




268 




39 5 




3 60 


- 15 1 


- 


22 


- 


31 1 


- 


35 6 


- 


29 5 


- 


11 1 




15 4 




42 2 





68 



Table 94. Computed values of secular change in the vertical gradient of vertical component of magnetic 
field intensity ( 3Z/ 3r), main field, for 1912.5 expressed in units of 10-14 CGS per year 



Geographic 
east 






Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


24 8 22 2 


4 9 


_ 


20 4 


- 


382 


_ 


35 9 


- 13 8 


14 2 


30 5 


60 


29 2 33 


15 4 


- 


23 9 


- 


686 


- 


9 6 4 


- 95 7 


- 75 1 


- 56 8 


90 


27 4 280 


12 


- 


15 8 


- 


410 


- 


47 9 


- 29 2 


9 1 


49 2 


12 


216 16 9 


70 




1 2 




4 4 




13 4 


21 4 


24 5 


23 1 


15 


167 12 1 


8 8 




77 




70 




5 8 


6 5 


10 9 


15 8 


180 


14 5 16 2 


25 6 




35 




35 8 




28 5 


22 7 


27 2 


39 9 


210 


14 2 18 9 


28 7 




34 5 




305 




19 2 


87 


3 8 


20 


24 


15 2 23 1 


32 9 




33 4 




219 




6 6 


2 


5 8 


1 8 2 


2 70 


16 4 315 


577 




73 7 




581 




7 9 


- 54 8 


- 95 2 


- 90 9 


3 


15 9 27 6 


55 3 




80 3 




74 4 




24 8 


- 4 9 4 


-105 


-10 6 2 


33 


15 113 


16 2 




34 8 




619 




84 4 


927 


88 8 


84 5 


3 60 


181 7 2 


9 2 


- 


177 


- 


7 6 




19 2 


504 


73 6 


84 6 




Geographic 
east 






Geographic colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 




130 




140 




150 


160 


170 




























30 


24 6 - 12 


- 34 4 


.. 


613 


_ 


72 6 


w 


66 1 


- 4 6 


- 20 8 




60 


- 602 - 869 


-1197 


- 


1350 


- 


119 5 


- 


78 3 


- 317 


19 




90 


69 7 58 4 


21 4 


- 


187 


- 


371 


- 


24 7 


3 5 


18 4 




120 


17 7 7 9 


4 9 


- 


136 


- 


83 




12 3 


34 4 


34 4 




150 


140 15 


- 15 3 


- 


21 8 


- 


71 




22 8 


45 8 


39 2 




180 


4 8 1 410 


20 9 




3 7 




3 8 




20 1 


351 


29 2 




210 


4 - 18 


- 35 4 


- 


45 6 


- 


413 


„ 


24 1 


4 5 


5 4 




24 


22 7 90 


- 217 


- 


56 9 


- 


80 l 


- 


79 9 


- 57 2 


- 24 4 




2 70 


-497- 60 


4 9 


- 


26 2 


- 


760 


- 


1066 


- 94 5 


- 4 8 4 




3 


-54 118 


418 




14 5 


- 


47 9 


- 


98 3 


-1012 


- 57 9 




3 30 


87 4 915 


79 9 




4 06 


- 


177 


- 


67 8 


- 815 


- 52 2 




3 60 


86 9 82 4 


672 




36 3 


- 


6 3 


- 


43 9 


- 567 


- 37 7 





Table 95. Computed values of secular change in the vertical gradient of vertical component of magnetic 
field intensity ( 8Z/3r), main field, for 1922.5 expressed in units of 10-14 CGS per year 



Geographic 
east 






Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


16 5 4 9 


92 


m 


25 1 


_ 


37 2 


_ 


37 6 


- 22 6 


1 5 


19 3 


60 


196 135 


9 


- 


23 7 


- 


55 9 


- 


79 1 


- 77 2 


- 497 


- 16 8 


90 


22 162 


5 4 


- 


11 9 


- 


31 9 


- 


43 5 


- 34 


2 


44 3 


120 


23 9 16 4 


66 


- 


4 


- 


2 6 


_ 


9 


30 


8 9 


148 


150 


270 22 1 


14 3 




60 


- 


8 


- 


40 


4 


96 


19 9 


180 


307 32 1 


32 3 




31 1 




27 2 




21 3 


17 5 


188 


23 9 


210 


33 2 35 9 


32 9 




25 7 




17 3 




10 5 


.6 2 


37 


1 8 


24 


33 8 38 3 


360 




28 6 




20 4 




13 9 


86 


2 5 


3 5 


2 70 


321 42 4 


55 8 




65 3 




59 9 




324 


- 10 8 


- 504 


- 65 5 


30 


26 9 34 7 


52 5 




70 5 




707 




411 


87 


- 507 


- 57 5 


330 


19 9 146 


18 9 




36 6 




618 




816 


87 3 


81 8 


767 


3 60 


157 12 


- 112 


- 


13 8 


- 


3 5 




16 5 


392 


58 9 


730 




Geographic 
east 






G( 


;ographi 


c colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




30 


15 1 - 149 


- 58 5 


.. 


938 


m 


103 3 


_ 


85 2 


-* 53 4 


- 271 




60 


6 4-320 


- 796 


- 


116 9 


- 


116 9 


- 


79 8 


- 321 


66 




90 


74 2 69 8 


336 


- 


9 1 


- 


29 3 


_ 


174 


73 


132 




120 


16 3 95 


2 9 


- 


10 9 


- 


3 9 




167 


337 


24 8 




150 


212 96 


77 


- 


16 1 


- 


5 5 




180 


337 


22 1 




180 


26 5 213 


9 3 


- 


1 3 


- 


2 9 




44 


110 


47 




210 


2 - 3 9 


- 108 


- 


212 


- 


31 8 


- 


371 


- 33 2 


- 23 3 




240 


87-14 8 


- 27 4 


- 


502 


- 


77 3 


- 


93 6 


- 85 1 


- 53 9 




270 


- 513 - 25 6 


- 171 


- 


416 


- 


87 3 


- 


1217 


-116 7 


- 72 5 




30 


- 256 183 


363 




7 9 


- 


517 


- 


1034 


-112 8 


- 754 




330 


79 9 85 6 


771 




417 


- 


14 5 


- 


66 1 


- 857 


- 63 9 




3 60 


796 748 


54 3 




18 4 


- 


23 3 


- 


54 9 


- 62 8 


- 46 1 





69 



Table 96. Computed values of secular change in the vertical gradient of vertical component of magnetic 
field intensity ( 9Z/ 3r), main field, for 1932.5 expressed in units of 10-14 CGS per year 



Geographic 
east 








Geographi 


c colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


30 


12 5 


71 


- 311 


- 


49 7 


_ 


53 1 


_ 


37 5 


- 10 


14 9 


22 1 


60 


81 


- 12 7 


- 35 6 


- 


566 


- 


70 4 


- 


70 3 


- 52 7 


- 22 2 


5 6 


90 


7 6 


9 4 


- 23 2 


- 


31 


- 


32 3 


- 


25 


4 5 


30 


6 9 1 


120 


10 6 


16 


- 10 4 


- 


149 


- 


15 7 


- 


13 3 


7 


1 9 


8 9 


15 


15 8 


9 2 


2 9 


- 


5 1 


- 


12 8 


- 


12 9 


4 


19 2 


312 


180 


21 4 


19 9 


19 5 




17 3 




12 6 




101 


15 5 


28 4 


3Q 7 


210 


26 4 


25 5 


23 2 




20 3 




16 6 




130 


10 7 


105 


1 6 


24 


310 


32 6 


32 4 




33 7 




35 4 




33 3 


24 6 


12 


1 8 


2 70 


34 4 


42 7 


514 




5 8 1 




5 3 4 




28 1 


- 140 


- 53 5 


- 6 7 5 


3 


34 


42 8 


50 9 




56 2 




52 1 




327 


1 7 


- 25 6 


- 313 


33 


2 8 4 


27 8 


24 2 




25 9 




39 6 




62 7 


83 7 


918 


8 6 


3 60 


20 1 


7 5 


- 10 3 


- 


21 7 


- 


15 4 




8 8 


39 4 


60 5 


6 3 2 




Geographic 
east 








Ge 


ographi 


c colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 




130 


140 


150 


160 


170 




3 


4 6 


- 316 


- 712 


- 


97 1 


_ 


99 8 


_ 


81 2 


- 52 8 


- 28 9 




60 


12 4 


- 10 4 


- 52 


- 


86 9 


- 


92 


- 


64 8 


- 260 


5 3 




90 


93 8 


88 2 


5 4 5 




14 6 


- 


5 3 




2 7 


21 1 


19 




12 


7 2 


4 


- 15 8 


- 


142 




7 4 




384 


54 4 


34 6 




150 


22 5 


3 7 


- 27 5 


- 


26 8 




2 6 




4 6 


56 2 


32 5 




180 


38 4 


22 5 


2 1 


- 


7 3 




4 




16 8 


24 2 


10 9 




210 


7 3 


2 5 


- 184 


- 


35 4 


- 


464 


- 


46 4 


- 36 4 


- 23 9 




24 


36 


9 9 


- 268 


- 


57 7 


- 


918 


- 


109 4 


- 96 5 


- 58 3 




2 70 


- 49 4 


- 181 


5 6 


- 


30 8 


- 


817 


- 


122 8 


-122 5 


- 7 8 3 




3 


-103 


216 


35 9 




12 9 


- 


4 5 


- 


93 2 


-110 3 


- 79 3 




3 3 


74 1 


63 1 


50 4 




26 


- 


143 


- 


58 2 


- 816 


- 66 7 




3 60 


508 


317 


12 2 


— 


9 3 


- 


32 9 


- 


54 1 


- 62 


- 4 8 9 





Table 97. Computed values of secular change in the vertical gradient of vertical component of magnetic 
field intensity ( dZ/ 8r), main field, for 1942.5 expressed in units of 10-14 CGS per year 



Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


10 


20 


30 




40 




50 


60 


70 


80 


90 


3 


6 2 


- 24 3 


- 415 


- 


52 5 




53 2 


_ 


410 


- 17 4 


9 3 


24 6 


60 


- 10 


- 314 


- 49 9 


- 


62 7 


- 


69 4 


- 


6 6 8 


- 49 


- 16 1 


19 9 


90 


-105 


- 315 


- 43 3 


- 


412 


- 


300 


- 


15 5 


3 1 


310 


661 


12 


6 8 


- 24 9 


- 33 7 


- 


27 5 


- 


12 5 


_ 





4 1 


37 


5 4 


15 


2 


- 10 9 


- 169 


- 


14 


- 


6 3 


- 


2 


1 8 


27 


5 5 


1 80 


78 


4 1 


2 9 




7 8 




16 8 




24 2 


26 8 


25 3 


23 


210 


12 8 


107 


5 4 




2 2 




2 6 




41 


3 6 


8 


17 


2 4 


14 4 


118 


8 1 




118 




22 8 




32 2 


30 9 


18 7 


4 5 


2 70 


130 


9 6 


90 




18 




29 2 




27 5 


5 8 


- 24 4 


- 419 


3 


9 5 


3 9 


2 4 




113 




24 5 




29 3 


206 


8 2 


8 4 


3 3 


47 


3 4 


5 5 




7 2 




32 4 




57 3 


69 9 


6 8 5 


613 


3 60 


8 


- 13 5 


- 22 7 


— 


21 5 


— 


8 8 




104 


29 3 


42 4 


46 5 




Geographic 
east 








Geograpru 


c colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 




130 




140 




150 


160 


170 




























3 


15 2 


- 305 


- 67 5 


_ 


1003 


_ 


99 5 


_ 


65 3 


- 190 


11 1 




60 


383 


24 4 


- 15 2 


- 


536 


- 


62 1 


- 


339 


8 5 


29 9 




90 


9 4 6 


99 


74 9 




391 




17 9 




23 9 


42 9 


446 




120 


106 


15 1 


15 5 




162 




249 




42 8 


56 8 


4 81 




150 


9 3 


105 


8 4 




81 




15 9 




310 


42 4 


36 4 




180 


21 


171 


8 9 


- 


17 


- 


90 


- 


71 


2 5 


114 




21 


30 


6 7 


- 18 4 


- 


392 


- 


60 5 


- 


677 


- 517 


- 191 




24 


4 4 


- 117 


- 28 8 


- 


615 


- 


9 8 5 


- 


115 8 


- 95 3 


- 436 




2 70 


- 35 4 


- 17 2 


- 138 


- 


411 


- 


870 


_ 


1177 


-105 4 


- 52 6 




30 


26 4 


47 9 


482 




14 8 


- 


388 


_ 


806 


- 83 2 


- 45 




330 


56 8 


53 6 


42 1 




15 2 


- 


21 1 


- 


49 2 


- 52 1 


- 27 5 




3 60 


39 9 


21 6 


5 5 


- 


336 


- 


51 3 


- 


504 


- 32 3 


7 8 





70 



Table 98. Computed values of secular change in the vertical gradient of north component of magnetic field 
intensity ( 8X/ 8r), residual field, for 1942.5 expressed in units of 10-14 CGS per year 



Geographic 
east 








Geograph 


c colatitude in 


degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


23 2 


2 2 5 


15 2 




2 2 


_ 


14 1 


_ 


29 7 


- 37 6 


- 307 


7 5 


60 


29 8 


27 R 


19 2 




7 3 


- 


7 1 


- 


2 5 


- 42 9 


- 50 8 


- 3 R 6 


90 


28 4 


22 


5 7 


- 


1 1 R 


- 


24 7 


- 


34 2 


- 4 3 8 


5 9 


- 4 6 3 


12 


20 3 


13 9 


19 


- 


17 5 


- 


24 2 


- 


2 1 R 


- 16 8 


- 15 1 


- 15 6 


15 


7 9 


4 5 


4 8 


- 


13 2 


- 


15 7 


- 


13 


9 7 


R 7 


R 7 


180 


3 9 


4 2 


9 1 


- 


14 3 


- 


15 5 


- 


117 


6 1 


IP 


7 


2 10 


- Ill 


5 R 


4 4 


- 


5 7 


- 


6 


- 


3 3 


1 


4 4 


6 


2 4 


- 13 9 


7 5 


R 5 


- 


1 2 R 


- 


12 3 


- 


3 1 


9 9 


1 R 2 


18 4 


2 70 


- 13 1 


9 4 


- 13 A 


- 


16 1 


- 


7 2 




12 1 


2 B 4 


27 6 


10 6 


3 


R7 


R 5 


- 1 5 R 


- 


215 


- 


17 


- 


3 4 


7 7 


5 4 


6 9 


3 3 


4 


d 


- 17 3 


~ 


32 5 


- 


3 R 9 


- 


316 


- 15 9 


19 


5 2 


3 6 


114 


R 2 


2 8 


- 


1 7 R 


- 


29 6 


- 


33 3 


- 27 9 


- 15 4 


1 3 




Geographic 
east 








Geographic colatitude in 


degrees 






longitude 
in degrees 


100 


110 


120 




130 




140 




150 


160 


170 




























3 


2 3 5 


4 6 4 


4 6 2 




20 3 


_ 


15 5 


_ 


405 


- 39 1 


- 13 9 




60 


7 1 


27 8 


4 3 5 




2P 8 


- 


5 2 


- 


314 


- 27 4 


5 9 




90 


- ? 4 


9 


34 3 




36 1 




17 1 


- 


1 7 


1 7 


29 6 




12 


- 13 5 


69 


6 


- 





- 


3 R 


- 


1 9 


14 2 


4 R 




15 


6 5 


2 2 


3 


- 


1 7 


- 


5 3 


- 


2 6 


112 


31 3 




l a o 


3 9 


9 1 


13 9 




14 3 




R 4 




2 


2 9 


3 1 




2 10 


R 7 


15 6 


2 4 5 




27 8 




1 n i 


- 


3 9 


- 26 3 


- 33 2 




2 4 


16 6 


216 


33 R 




413 




29 3 


- 


4 3 


- 4 2 7 


- 60 7 




2 7 


5 4 


2 


21 R 




45 6 




44 1 




101 


- 37 1 


- 6 6 5 




3 


- 140 


11 


29 8 




5R 4 




611 




30 5 


- 16 9 


- 53 3 




3 30 


9 7 


19 6 


36 4 




50 7 




4 9 2 




26 6 


7 8 


- 35 9 




3 6 


19 4 


34 7 


4 17 




35 7 




17 5 


- 


5 2 


- 217 


- 24 5 





Table 99. Computed values of secular change in the vertical gradient of east component of magnetic field 
intensity ( 8 Y/ 8r), residual field, for 1942.5 expressed in units of 10-14 CGS per year 



Geographic 
east 








Geographic colatitude in 


degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70. 


80 


90 


30 


- 17 7 


- 19 3 


- 214 


_ 


24 5 


_ 


27 9 


_ 


300 


- 2 9 3 


- 2 5 5 


- 2 2 


60 


5 3 


3 7 


2 




4 R 




R 2 




101 


12 3 


17 6 


27 3 


90 


8 8 


10 7 


14 7 




20 3 




24 9 




25 4 


20 2 


10 7 


1 


12 


20 


19 7 


16 9 




12 1 




6 


- 


5 


7 5 


- 15 


- 22 3 


15 


24 8 


2 4 4 


22 3 




19 2 




16 4 




14 4 


13 6 


13 2 


12 4 


1 fl 


214 


18 3 


13 8 









4 9 




1 6 


13 


4 5 


7 9 


210 


12 7 


8 8 


4 9 




1 9 







- 


1 2 


2 4 


3 8 


- . 5 6 


24 


2 9 


3 


5 8 




1 O 




12 7 




115 


6 


12 


6 9 


2 70 


6 7 


4 5 


2 5 


- 


2 2 


- 


4 5 


- 


R 2 


- 10 R 


9 4 


3 


3 


- 15 4 


- 119 


7 2 


- 


4 




9 3 




213 


33 


413 


4 3 7 


3 3 


- 219 


- 20 2 


- 1 R 6 


- 


167 


- 


13 7 


- 


9 4 


5 


2 3 


3 2 


3 60 


- 23 6 


- 25 4 


- 29 


- 


33 4 


- 


36 2 


- 


34 9 


- 28 9 


- 20 9 


- 15 2 




Geographic 
east 








Geographi 


c colatitudt 


» in 


degrees 








longitude 
In degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


- 15 4 


- 12 8 


- 117 


_ 


9 7 


_ 


3 3 




9 2 


26 9 


4 5 7 




60 


4 3 


52 8 


60 9 




62 5 




5R 7 




52 8 


4 R 


45 5 




90 


40 


14 


8 3 




216 




33 




* 3 R 4 


36 2 


27 7 




12 


- 27 8 


- 29 5 


- 25 9 


- 


17 7 


- 


R 


- 


1 1 


5 


6 6 




15 


10 5 


70 


1 7 


- 


5 5 


- 


14 8 


- 


25 6 


- 36 1 


- 4 3 4 




1 80 


- 110 


- 14 


- 18 


- 


24 8 


- 


35 7 


- 


49 5 


- 619 


- 67 2 




2 10 


7 8 


- Ill 


- 16 9 


- 


26 2 


- 


38 8 


- 


52 5 


- 63 1 


- 66 4 




24 


8 7 


7 1 


5 1 


- 


6 4 


- 


12 6 


- 


22 4 


- 32 6 


- 4 




2 70 


71 


17 9 


260 




29 1 




26 9 




20 1 


100 


2 2 




3 


40 4 


34 2 


29 1 




27 7 




29 9 




32 6 


32 3 


26 7 




3 30 


7 5 


- 13 1 


- 16 5 


- 


141 


- 


4 8 




9 8 


25 8 


38 6 




3 60 


- 15 7 


- 22 6 


- 317 


- 


36 2 


- 


30 1 


— 


117 


14 7 


415 





71 



Table 100. Computed values of secular change in the vertical gradient of vertical component of magnetic 
field intensity ( 3Z/ 3r), residual field, for 1942.5 expressed in units of 10-14 CGS per year 



Geographic 
east 










Geographic colatitude 


in 


degrees 






longitude 
in degrees 


10 


20 


30 


40 


50 


60 


70 


80 


90 


3 


- 1 .5 1 


- 33 1 


_ 


50 


_ 


6 0/. 


_ 


sm 




470 


— P O 1 


5 9 


q 


6 


- 1 8 R 


- 4 1 


- 


5 P 3 


- 


7 0S 


_ 


7 6 4 


_ 


72 7 


- 5 3 7 


- 19 4 


17 8 


Q 


19 2 


^Ol 


- 


5 1 5 


- 


4 P. 7 


- 


36 6 


_ 


2 9 


9 


2 8 3 


r-, £ e, 


1 o o 


- 15 4 


- 3 3 2 


- 


4 1 4 


- 


3 4 3 


- 


1.83 


_ 


4 6 


8 


1 R 


4 8 


1. ,S0 


PP. 


- 18 8 


- 


P. A 


- 


2 2 


- 


113 


_ 


4 


4 


1 9 


3 7 


1 8 


4 


3 5 


- 


3 8 




2 1 




12 3 




2 1 2 


2 5 2 


2 5 3 


2 18 


?, 1 


4 6 


3 2 


- 


1 


- 


3 1 


- 


1 4 




1 5 


2 5 


1 2 


2 


2 4 


6 2 


4 3 




1 5 




6 3 




18 7 




20 8 


2 9 6 


19 


q 3 


2 7 


4 7 


1 9 




P, P, 




12 1 




2 4fi 




2 4 2 


4 O 


- 9 4 7 


/l O 4 


3 


1 1 


4 


- 


4 9 




4 9 




19 2 




2 5 3 


1 R 


7 1 


103 


3 3 


3 8 


- 117 


- 


1 3 4 




2 




26 3 




5 2 4 


6 6 3 


6 6 3 


6 3 1 


3 60 


9 6 


- 2 2 1 


- 


3 1 


- 


2 9 1 


- 


15 5 




4 8 


2 4 9 


304 


4 7 7 






Geographic 
east 








Geographic colatitude 


in 


degrees 








longitude 
in degrees 


100 


110 


120 


130 


140 


150 


160 


170 




3 


1 R 7 


1 4 


_ 


5 8 8 


_ 


1 7 6 


_ 


12 9 9 




1 Q 1 


5^5 


5 4 




60 


36 p 


2 8 1 


- 


1 2 5 


_ 


6 8 6 


- 


10 7 6 


_ 


10 3 9 


5 9 2 


- 3 3 




o 


p 9 n 


9 6 1. 




7 2 




22 


- 


2 8 5 


_ 


5 1 3 


- 37 7 


£.9 




IPO 


2 7 


7 2 









2 9 


_ 


8 2 


_ 


1 5 6 


— 12 9 


2 1 




1 5 


1 7 


4 




1 1 




3 7 




6 5 




7 


4 3 


1 1 




1 PO 


16 


8 4 




4 1 




5 4 




9 7 




117 


R 6 


2 9 




2 10 


3 5 


- 109 


- 


1 8 4 


- 


2 R 


_ 


16 8 


_ 


O 9 


Q 


3 ^ 




2 4 





9 5 


- 


?q cj 


- 


3 5 4 


_ 


3 Q R 


_ 


30 9 


- 113 


6 6 




2 7 o 


- 2 6 8 


R 5 


- 


2 2 


- 


12 8 


- 


27 3 


_ 


? 7 4 


- P. K 


14 




3 


37 3 


6 17 




6 3 4 




39 2 




7 6 


_ 


7 1 


2 8 


22 3 




3 3 


67 4 


6 9^ 




5 8 




30 7 




1 4 


_ 


10 2 


2 2 


2 4 8 




3 6 


4 7 8 


3KS 




7 9 


- 


2 9 7 


- 


5 6 8 


- 


5 4 4 


- 2 2 1 


17 7 





Table 101. Spherical harmonic coefficients for the average annual secular variation 
expressed in units of 10-5 CGS 



Author 


Epoch 


«° 


s. 1 


»,' 


s 2 ° 


W 


■J 


82 2 


h 2 
h 2 


Dyson-Schmidt 1922-1885 


+ 20 


- 1 


- 1 


-10 


+ 


6 


-14 


+ 21 


-18 


Bartels 1920-1902 


+ 42 


- 9 


+ 12 


- 7 


+ 


8 


-25 


+ 13 


- 8 


Carlheim-Gyllenskold 1920-1902 





+ 13 


+ 4 





- 


4 


-12 


+ 13 


-17 




'1912.5 


+ 25 


+ 1 


- 7 


- 7 


- 


1 


- 9 


+ 24 


-17 


Vestine-Lange • 


1922.5 
1932.5 


+ 28 
+ 23 


+ 4 

+ 1 


- 7 

- 5 


-10 
-14 


+ 

+ 


1 
1 


-14 
-18 


+ 17 - 
+ 10 


-17 
-14 




J942.5 


+ 9 


+ 2 


+ 1 


-18 







-20 


+ 2 


-14 



72 



FIGURES 9-28 



Figure Page 

9-12. Current function in 10 4 amperes for thin spherical shell at depths 0, 1000, 2000, 

and 3000 km within Earth to reproduce geomagnetic secular change, epoch 1912.5 74 

13-16. Current function in 10 4 amperes for thin spherical shell at depths 0, 1000, 2000, 

and 3000 km within Earth to reproduce geomagnetic secular change, epoch 1922.5 76 

17-20. Current function in 10 4 amperes for thin spherical shell at depths 0, 1000, 2000, 

and 3000 km within Earth to reproduce geomagnetic secular change, epoch 1932.5 78 

21-24. Current function in 10 4 amperes for thin spherical shell at depths 0, 1000, 2000, 

and 3000 km within Earth to reproduce geomagnetic secular change, epoch 1942.5 80 

25-28. Current function in 10 4 amperes for thin spherical shell at depths 0, 1000, 2000, 
and 3000 km within Earth to reproduce residual (nondipole part) of geomagnetic 
change, epoch 1942.5 82 



73 




FIG. 9 -CURRENT-FUNCTION IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH ZERO WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1912.5 




FIG.IO-CURRENT-FUNCT/ON IN 10* AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 1000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1912.5 

74 




FIG. //-CURRENT-FUNCTION IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 2000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1912.5 




FIG.I2-CURRENT-FUNCTI0N IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 3000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1912.5 



75 




FIG. 13-CURRENT-FUNCTION IN 10* AMPERES FOR THIN SPHERICAL SHELL AT DEPTH ZERO WITHIN EARTH TO REPRO 

DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1922.5 * 




FIG.I4-CURRENT-FUNCTI0N IN 10* AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 1000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1922.5 



76 




FIG.I5-CURRENT-FUNCTI0N IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 2000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1922.5 




FIG. 16-CURRENT-FUNCTION IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 3000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1922.5 

77 




FIG.I7-CURRENT-FUNCTI0N IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH ZERO WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1932.5 




FIG. 18-CURRENT-FUNCTION IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 1000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1932.5 

78 




FIG. 19-CURRENT-FUNCT/ON IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 2000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1932.5 




FIG2O-CURRENT-FUNCTI0N IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 3000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1932.5 



79 




FIG.2I-CURRENT-FUNCTI0N IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH ZERO WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1942.5 




FIG. 22-CURRENT- FUNCTION IN lO 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 1000 KM WITHIN EARTH TO 

DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1942.5 

80 



RE PRO- 




F/G.23-CURRENT-FUNCTI0N IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 2000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1942.5 




F/G.24-CURRENT-FUNCT/0N IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 3000 KM WITHIN EARTH TO REPRO- 
DUCE GEOMAGNETIC SECULAR CHANGE, EPOCH 1942.5 

81 




FIG. 25-CURRENT-FUNCTION IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH ZERO WITHIN EARTH TO REPRO- 
DUCE RESIDUAL (NON-D/POLE PART) OF GEOMAGNETIC CHANGE, EPOCH 1942.5 




FIG. 26— CURRENT-FUNCTION IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 1000 KM WITHIN EARTH TO REPRO- 
DUCE RESIDUAL (NON-D/POLE PART) OF GEOMAGNETIC CHANGE, EPOCH 1942.5 

82 




FIG. 27— CURRENT-FUNCTION IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 2000 KM WITHIN EARTH TO REPRO- 
DUCE RESIDUAL (NON-DIPOLE PART) OF GEOMAGNETIC CHANGE, EPOCH '942.5 




\--lr-VtV-Vrv-V--l— 



FIG. 28-CURRENT FUNCTION IN I0 4 AMPERES FOR THIN SPHERICAL SHELL AT DEPTH 3000 KM WITHIN EARTH TO REPRO- 
DUCE RESIDUAL (NON-DIPOLE PART) OF GEOMAGNETIC CHANGE, EPOCH 1942.5 



83 



CHAPTER IV 
THE GEOMAGNETIC VARIATION WITH SUNSPOT -CYCLE, RV 



The dependence of the annual mean values of the geo- 
magnetic elements on solar activity has been demonstrat- 
ed and examined by Moos [16], Schmidt [17], McNish 
[18], Scott [19], Wasserfall [20], and Chapman and 
Bartels [3]. It was noted that the annual mean in H are 
usually smaller in sunspot maximum years than in sun- 
spot minimum years, and that this was a consequence of 
the greater incidence in the number of magnetic storms 
near sunspot maximum. The possibility that the effect 
might be due to a variation, with sunspot-cycle, of the 
secular variation arising from causes within the Earth 
was hence discounted by Fisk [21]. 

Schmidt [17] in his study used smoothed values of 
the annual means in three elements for Potsdam, and he 
derived normal values of field defined by annual means 
centered on individual months. He achieved considerable 
success in fitting the smoothed annual means at Pots*dam 
by a quadratic expression involving the time, except for a 
part left over which varied with sunspot number. A der- 
ivation of RV is rendered difficult because the period of 
the variation is about 11 years, and thus is too long to 
permit very satisfactory derivation of its average char- 
acteristics from the short series of data available at 
most stations. Wasserfall [20] recently satisfactorily 
used nearly 100 years of data for Oslo, but few stations 
can be analyzed with confidence by a graphical method 
because the series of observations is too short. 

The first attempt to derive RV on a world-wide scale 
was made by Fisk [21], for the H-component at ten ob- 
servatories, and particular attention was given to the im- 
portance of the effect in his estimates of secular varia- 
tion. He also considered the differences in the value of 
RV resulting from the use of days differing as to the de- 
gree of disturbance, and showed that the effect persisted 
with only slightly reduced amplitude even on selected qui- 
et days. 

The present work consists essentially of an extension 
of the work of Fisk, using more complete data since made 
available, with particular emphasis on the construction of 
tables permitting reduction of field-observations to their 
normal values, for the period 1905 to 1940. Annual mean 
values of the magnetic elements collected and compiled 
by Fleming and Scott [22], comprise the data analyzed. 

Following Schmidt [17] smoothed biyearly means B 
of the geographic north (X), east (Y), and vertical (Z) 
components were first obtained. The values B were then 
fitted by various formulas at a few stations to observe 
whether the more slowly varying part of B afforded by 
the main field could be successfully fitted, yielding a 
part left over which would be approximately the same in 
form at neighboring observatories. 

It was found that a power series in time t of the form 
R = A + Bt + Ct 2 + Dt3, where A, B, C, and D are con- 
stants, appeared to remove also a part possibly associ- 
ated with the sunspot-cycle. The term Dt3 was accord- 
ingly dropped. The form R = A + Bt + Ct 2 was next fit- 
ted by the method of least squares to the values B, with 
considerably more encouraging results. Also, longer se- 
ries of data for B were used and fitted by R = A + Bt + 



+ bj sin at + b£ sin 2 at + b3 sin 3 at, where a was 
taken to be 13° 20', so that the terms had periods of 54, 
36, and 18 years, using a procedure somewhat similar to 
that employed by Fisk, who used periods of 48, 24, and 16 
years. The justification for this pfocedure was that it ap- 
peared to work moderately well. The choice of period 
was such that periods of 11, 22, and 33 years, roughly in- 
dicated as present by successive differences of B for 
1900 to 1940 at various stations, would be badly fitted. 
However, there is the obvious defect that the supposed 
values of RV in general would be partially fitted what- 
ever the choice of period. Moreover, it is an obvious 
point that any smoothly varying function will not be fitted 
perfectly by an expression which is the sum of a constant, 
a linear term, and only three periodic terms. An alter- 
native method was considered, based on the fitting of all 
periodic changes of RV when using a period of nearly 11 
years, but this would be open to other objections and was 
accordingly discarded. 

Figure 29 shows the results obtained using the ex- 
pression with periodic terms in fitting the values B at 
many stations. In the geomagnetic north component the 
agreement, station by station, appears on the whole quite 
good, the results apparently being least consistent at 
Ston'yhurst, for which annual means based on absolute ob- 
servations only were available, and at Apia and Pilar in 
the Southern Hemisphere. It will be noted that the latter 
two stations also appear inconsistent with each other, 
with Pilar showing some resemblance to the results for 
the Northern Hemisphere. 

In the case of the geomagnetic east and vertical com- 
ponents the results appear, on the whole, considerably 
less consistent station by station than in the case of the 
geomagnetic north component. 

Certain defects arising from the mode of estimating 
RV should be reduced on averaging results for a number 
of stations. 

Accordingly, the values for the first ten stations, 
excluding Stonyhurst, were meaned separately in the 
three components, and, using the known latitude distribu- 
tion of disturbance given by D m j, the equatorial value of 
RV in X' was computed. The latitude distribution was 
then used to yield the computed values in the X' -compo- 
nent at each station, indicated by the smooth curves in 
Figure 29. The fit, station by station, appears to be about 
as good as might be expected in the north component, but 
the theoretical values for the east and vertical compo- 
nents which are to be compared with observed values are 
zero or practically zero (these are not shown because of 
difficulties of representation for the stations of Figure 
29) and thus are in poor agreement with observation. 

A different derivation of RV is afforded from the fit 
of the annual means by using the power series R = A + 
Bt + Ct 2 . Figure 30 gives the results so obtained com- 
pared with the computed values of RV. The computed 
values were obtained, as before, for the X' -component at 
each station, using an equatorial value of RV estimated 
from means for the six stations, Sloutsk, Valencia, Rude 
Skov, De Bilt, Potsdam, and Val Joyeux. Good agreement 



85 



86 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



is on the whole again indicated for the geomagnetic north 
component, whereas the (small) east and vertical com- 
ponents (not shown) presumably remain unsatisfactorily 
defined on the basis of observation. 

The comparison of Figure 30 is extended to include 
all additional stations for the geomagnetic north compo- 
nent in Figure 31, with similar satisfactory features in 
general evidence, except possibly for the stations noted 
for the Southern Hemisphere. 

Figure 32 compares observed values of biyearly dif- 
ference in B with thoee computed by the periodic formu- 
la whose constants were separately determined for each 
component, at each station, by fitting the values B from 
observation. The smoother characteristics of the bi- 
yearly differences given by the formula are clearly in 
evidence, in accordance with the assumption that the 
Earth's main field changes gradually and not discontinu- 
ously with time. This comparison shows that a fairly 
good fit of the observed data is obtained using such a 
formula, but this does not mean that the directly corre- 
sponding values in RV of Figure 29 are accurate; their 
accuracy is dictated by the quality of the observed data. 

Figure 33 presents the means for the ten stations of 
the Northern Hemisphere in the geomagnetic north com- 
ponent of RV as found from the fit by formula with peri- 
odic terms, and for the mean of six stations referred to 
above as derived with the aid of the finite power series 
of three terms. 

The results obtained using two imperfect methods 
give fair agreement in the estimated equatorial values of 
RV (we have not taken the trouble to compute the mean 
of the same ten stations for (B) as used for (A) ). For 
(A), due to the formula used in fitting, estimates of RV 
are expected to be defective for early years of observa- 
tion. Moreover, there is an undesirable arbitrary feature 
in fitting data by the so-called sinusoidal formula in that 
we have assigned the value a = 13° 20' ; it was found 
that a change in a of only a few degrees changed the es- 
timated RV by as much as 10 per cent. In the fit of data 
by the power series, the results in RV for the first and 
last few years may be bad because it seems unlikely that 
one could extrapolate so simple a formula for years prior 
to 1905 and following 1937 without gross errors. Howev- 
er, it seems considerably simpler to assume that the 40 
years of data may be better fitted by a terminating power 
series, using a quadratic formula for, say, 25-year in- 
tervals overlapping in time. Our experience indicates 
that this assumption is at least fairly well substantiated. 
Hence, we regard the values of RV shown in Figure 30 
as our better approximation over the years indicated. 



The results seem in fair agreement with expectation of 
slow systematic change with latitude and with variation 
in the degree of magnetic disturbance with sunspot-cycle, 
in the X' -component. In Y' we have been much concerned 
by the large and unexpected amplitude of RV. There is 
in evidence at De Bilt, Potsdam, and Val Joyeux, stations 
close together, considerable similarity in the Y' -compo- 
nent of RV. Values for Dehra Dun and Alibag, in another 
locality, likewise agree well with one another, though not 
with European stations. It seems likely that the similar- 
ities found locally are best explained as arising mainly 
from the inadequate representation of the generally much 
larger local phenomena of secular change by the simple 
power series. If this be true, all values shown for Y' 
could well be fictitious, the true values being about zero, 
as expected from consideration of yearly means of Y'. 
In the case of the Z' -component, it is well known that 
measured results are of doubtful accuracy; the results 
of Figure 30 emphatically indicate the immediate need 
for drastic changes in the present instrumentation and 
practices for measuring Z, in order that magnetic ob- 
servatories may obtain more accurate and useful values. 

Shown in Figure 34 are the corresponding latitude 
distributions in the X' -component, as given by the values 
of RV meaned in yearly magnitude for each station, over 
the period 1905 to 1940. In the Northern Hemisphere es- 
pecially, the latitude distributions found are clearly in 
good agreement with those also shown for D m j, thus jus- 
tifying the use of the latter in the earlier computations 
and comparisons for RV; it seems likely that the latitude 
distributions adopted are also applicable for the Southern 
Hemisphere. 

Assuming then that the variation RV is a consequence 
of disturbance of form D m i, approximate tables for the 
reduction of field-observations were constructed appli- 
cable in any latitude for the period 1905 to 1940 covered 
by the foregoing analysis. Tables 1-J and 1-K in the pre- 
ceding volume [1] list the adopted values, for which it is 
apparent only a moderate degree of accuracy can be 
claimed. 

The variation RV is of considerable theoretical in- 
terest due to its possible application in estimating the 
electric conductivity at greater depths within the Earth 
than has been possible from the use of daily and storm- 
time variations. However, there seems no possibility of 
making such estimates at the present time; they must 
await greatly improved control of recordings of vertical 
intensity. Therefore, the calculations can scarcely be 
made until some decades hence. 



FIGURES 29-34 

Figure Page 

29. Estimated geomagnetic components of variation of annual means with sunspot-cycle (RV) . 88 

30. Values of (RV) given by smoothed biyearly means 89 

31. Yearly residues for smoothed biyearly means 90 

32. Comparison of observed two-year differences in biyearly means 91 

33. Equatorial values of (RV) 92 

34. Comparison of latitude distribution 92 



87 




FIG. 29- ESTIMATED GEOMAGNETIC COMPONENTS OF VARIATION OF ANNUAL MEANS WITH SUNSPOT- CYCLE (PV)FPOM SMOOTHED BI-YEARLY 
MEANS (B), MINUS VALUES OF <B) FITTED BASIS LEAST SQUARES BY R - C * D (t - 1 ) + b, SIN a t + bg SIN 2 O-t + 6, SIN 3 at, WHERE d- I3°20' 
AND t THE TIME IN YEARS, COMPARED WITH MEAN VALUES (RV) FROM TEN STATIONS ASSUMING LATITUDE DISTRIBUTION THAT FOR DAILY 
MEANS OF DISTURBANCE (.GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



88 




FIG. 30- VALUES OF ( RV) GIVEN BY SMOOTHED Bl -YEARLY MEANS (B) MINUS VALUES R = o + bt + ct* FITTED TO (B) ON BASIS LEAST 

SQUARES COMPARED WITH ESTIMATED VALUES (RV) 



89 



tOOANKLYA 
<63°/>) 



LERWICK 
<62°S) 



MCA HOOK 

(6 fa) 



sitka 

(60°p) 



CSKDAL EMUIR 
(5*0) 



STONYHURST 
(5 7°/) 



VALENCIA 
(56° 6) 



SlOutsk 
(56° 0) 



RUDE SKOV 
(55°S) 



AGINCOURT 
(55' 0) 



ABINGER 
(S4°0) 



OE Bilt 
(5 3° 8) ' 



POT SO Ah 
(52°5> 



SEDDiN 
(52°4) 



IAL JOYEUX 
(5I°J) 



SHIDEf) 
(50°S) 



NANTES 

(so°s) 



CHEL TENHAM 
(50° I) 



KASAN 
(-9°!) 



KA THERINEBURG 
<4S°S) 



SAN MIGUEL 
(4S°6) 



1910 1930 1930 



K ^^" 



/N^- 




•**K^f 




^^ " ^g y *- 







.IK 



CO I MB f> A 
(4S°0) 



EBRO . 
(43°») 



SAN FERNANDO 
(4I°0) 



TUCSON 
(40° l) 



SAN JUAN 
(29°9) 



HELWAN 
(27° 2) 



ZINSEN 
(26°4) 



KAK I OH A 
(26°0) 



HONOLULU 
(2l°l) 



DEHRA dun 
(2o°s) 



ZO-SE 

(i9°e) 



A LI BAG 
(9° 5) 



ANTIPOLO 
(3°J) 



HUANCAYO 
(-0°6) 



VASSOURAS 
(-ll°9) 



PILAR . 
(-20° 2) 



MAURI T IUS 
(-26U) 



WA THEROO 
(-4I°S) 



TOOLANGI 
(-46° 7) 



1910 1920 1930 




■^Ao ^- 



^^ 




^7\^ 



-y r: w^ 



-^><^\ 



jx- 



FIG. 31-YEARLY RESIDUES FOR SMOOTHED BI-YEARLY MEANS (B) MINUS VALUES OF (B) FITTED BY R-UbV+CU*. WITH U THE TIME 
IN YEARS AND H.b.ANDC CONSTANTS COMPARED WITH ADOPTED VALUES OF GEOMAGNETIC VARIATION WITH SUNSPOT- 

CYCLE Ifiv), 1905-40 



90 




FIG. 32 — COMPARISON or OBSERVED TWO-YEAR DIFFERENCES IN THE Bt-YEARLY MEANS (B) OF COMPONENTS CORRECTED FOR SMOOTHING, GEOMAGNETIC 
VARIATION WITH SUNSPOT-CYCLE (RV^WITH VALUES COMPUTED FROM LATITUDE -DISTRIBUTION AND VALUE (RV), 1906-36 (.GEOMAGNETIC LATITUDES] 

INDICATED IN PARENTHESES) 



91 




FIG. 33- EQUATORIAL VALUES OF RV DERIVED USING LATITUDE DISTRIBUTION OF D^ IN X<- COMPONENT AND (A) 
MEAN RV IN X 1 , SINUSOIDAL FORMULA, (B) MEAN RV IN X 1 , POWER SERIES FORMULA 




FIG 34- COMPARISON OF LATITUDE DISTRIBUTION FOP AVERAGE YEARLY MAGNI- 
TUDE OF DEPARTURES OF GEOMAGNETIC VARIATION WITH SU NSPOT -CYC LE (RV> 
(POINT VALUES) WITH THAT OF DAILY MEANS OF DISTURBANCE (FULL LINE) 



92 



CHAPTER V 



THE GEOMAGNETIC ANNUAL VARIATION, AV 



1. General remarks. - -The annual variation is scarcely 
a distinct and unique natural phenomenon since it arises 
from seasonal changes in the magnitudes of other geo- 
magnetic variations. It is here conveniently regarded as 
the monthly mean departure from the annual mean value 
of a magnetic component, corrected for secular variation. 

Derivations of the annual variation are affected in ac- 
curacy by uncertainties in base-line values of variome- 
ters. Thus the monthly mean departures for all days of 
a month from the annual mean of all days will be more 
accurately defined at the observatories obtaining more 
accurate absolute observations. It appears likely that at 
most observatories the absolute observations from which 
we derive vertical intensity do not permit sufficient con- 
trol of variometers to indicate the annual variation at all 
in any individual year, except possibly in very high geo- 
magnetic latitudes where the annual variation in Z is 
relatively large and susceptible of measurement with 
smaller percentage of error. 

We first consider the general features found in the 
measured monthly departures fi om the annual means for 
various observatories of the Second International Polar 
Year, August, 1932, to August, 1933. Values averaged 
over different periods of years are next presented, and 
the general average latitude distribution of the annual 
variation AV is derived. 

2. The annual variation for all days, Polar Year, 
1932-33. — In order to obtain a general indication of the 
geographic distribution of AV with extensive coverage 
use was first made of the results for many observatories 
of the Polar Year, 1932-33. A and B of Figure 35 illus- 
trate the measured results, corrected for secular change 
at the various observatories, in terms of the geomagnetic 
north (X'-), geomagnetic east (Y'-), and vertical (Z-) 
components. 

A considerable degree of variability is shown, espe- 
cially in the case of the Z -component. Differences of 
this kind can only be partially attributed to local geomag- 
netic conditions. 

The agreement to within one or two gammas (one 
gamma = 10 _ 5 CGS-unit) between such widely separated 
stations as Cheltenham in North America and Swider in 
Europe is truly remarkable. Good agreements of this 
kind for stations of nearly the same geomagnetic latitude 
can hardly be accidental when obtained for several 
months in succession. Such agreements are no doubt a 
consequence of the excellence of the absolute instru- 
ments and of the techniques of their use at the observa- 
tories. It will be noted that the results for a number of 
other observatories located in similar latitudes show al- 
most identical results for the annual variation of the geo- 
magnetic north component. The results for Z at these 
observatories do not agree at all well, and it may be con- 
cluded that they are open to suspicion. In the case of the 
geomagnetic east component (Y'), it would appear that it 
is small in all latitudes, although near the auroral zone 
(near geomagnetic latitudes 65° to 70° north) some vari- 
ability from month to month is shown, presumably as the 
result of irregular disturbances there found predominating 



and because of the symmetry of the disturbance field 
about closed curves other than the parallels of geomag- 
netic latitude. 

In regions near the auroral zone, it would in fact be 
expected that there should at times be evidence of change 
in amplitude of the annual variation with longitude. Dur- 
ing magnetic storms the diurnally varying part, which 
depends mainly on local time in any region, would con- 
tribute unequally to the monthly means observed at sta- 
tions in different longitudes. This effect would be most 
notable in the cases of great magnetic storms, where the 
influences of a single storm would tend strongly to affect 
the mean monthly value at an observatory. 

It is of interest to see whether a selection of observa- 
tories can be made such that a systematic pattern is e- 
vinced in the latitude distribution of the annual variation. 
C of Figure 35 illustrates such a selection, using the data 
of A and B of Figure 35, the results for a few observa- 
tories being meaned. 

An orderly, simple change with geomagnetic latitude 
in the character of the annual variation of the geomagnet- 
ic north component is at once apparent. The annual var- 
iation in the geomagnetic east component appears to be 
nearly zero in all latitudes. In the case of the vertical 
component, the results are disappointing except in very 
high latitudes where the variation is clearly of larger 
amplitude, and where the use of special equipment to de- 
termine the base lines of Z variometers resulted in su- 
perior determinations. 

The values of the geomagnetic north component shown 
in Figure 35 can be analyzed into a part symmetrical a- 
bout the equator and a sinusoidal part of one-year period, 
with six months' difference in phase between the Northern 
and Southern Hemispheres. Cynk [23] showed that the 
symmetrical part in any latitude varied in amplitude di- 
rectly as the disturbed-day minus quiet-day means. Fig- 
ure 36 shows the results of such an analysis based on the 
data of C of Figure 35. The observed values AX' of the 
annual variation are conveniently regarded as comprising 
two parts with simple latitude distributions, one part sym- 
metrical about the equator, with minima near the equi- 
noxes, varying with latitude proportionately to the daily 
means of disturbance, the other a sinusoidal part, show- 
ing in the Northern Hemisphere a maximum near the 
winter solstice and a minimum near the summer solstice, 
and in the Southern Hemisphere a maximum and minimum 
of opposite phase. Table 102 gives the sinusoidal part of 
C of Figure 35 in the form of the Fourier series ag + aj 
cos x + bj sin x, where x is an angular representation 
of the time at a rate of 30° per month beginning on Sep- 
tember 1, 1932. Although there is evidence of system- 
atic variation of the coefficients aj and bj, the latitude 
distribution does not appear to be satisfactorily defined 
from data of a single year. 

Since the symmetrical part depends upon the average 
value of disturbance, the comparatively large annual var- 
iation for disturbed days was next derived. The results 
of Figure 36 indicate quite clearly that an accurate de- 
scription of the latitude distributions of the two parts of 



93 



94 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



the annual variation can be expected only from the aver- 
ages of many years of data. Although years of data for 
this purpose have not been obtained for polar regions, 
a certain amount of useful information respecting the 
latitude distributions in high latitudes is available from 
the results for the single year of observation provided 
by the Polar Year, 1932-33. 

A, B, and C of Figure 37 show the annual variations 
found for the Polar Year 1932-33, for international quiet 
days, international disturbed days, and for their differ- 
ences, for many stations. It is evident from A of Figure 
37 that the annual variation on quiet days closely re- 
sembles that found for all days, although somewhat 
smaller in amplitude than the latter. Thus the influences 
giving rise to at least the major part of the annual varia- 
tion are likewise operative on magnetically quiet days. 
This is mainly a consequence of disturbance, since the 
quiet-day means in the geomagnetic north component are 
lower in months when there are stronger and more fre- 
quent disturbances. Of quite special interest are the 
comparatively large annual variations in Z in high lati- 
tudes as shown by Thule ($ = 88°. 0), Godhavn ($ = 79°.8), 
and Juliannehaab ($ = 70°.8). 

In B of Figure 37 are shown the annual variations 
obtained for international disturbed days at polar sta- 
tions. These afford an interesting comparison with the 
corresponding values of A of Figure 37. The most sig- 
nificant difference is the increase in amplitude shown in 
all latitudes in the case of the geomagnetic north compo- 
nent, unaccompanied by a corresponding increase in the 
amplitude of the vertical component in high latitudes. In 
fact, the latter is only slightly larger on disturbed days 
than on quiet days. Thus, if we seek to explain the sinu- 
soidal part as due to electric currents above the Earth, 
flowing either from geomagnetic west to east or, prefer- 
ably, geomagnetic east to west (since the annual varia- 
tion in the geomagnetic east component is very small), 
there might be said to be such currents strongly in evi- 
dence on quiet days but not particularly strongly aug- 
mented on disturbed days. 

A significant feature here is that the increase in mag- 
nitude of the symmetrical part with increased intensity 
of disturbance is not accompanied by a corresponding 
proportional increase in the amplitude of the sinusoidal 
part. Hence the annual variation comprises two parts 
free to vary somewhat independently of each other. This 
means further that in order to predict the annual varia- 
tion in any latitude, from the observed annual variation 
at a particular latitude, the latitude distributions of the 
two parts of the annual variation must be independently 
derived, using corresponding latitude factors which, 
though related to the intensity of disturbance, will be in 
certain respects independent of each other. 

C of Figure 37 illustrates for the same stations the 
differences between the annual variations on disturbed 
and quiet days. The annual variation for disturbed minus 
quiet days is of particular interest in that it is less sus- 
ceptible to the influences of errors in base-line values 
and permits study also of the relationships of the two 
parts of the annual variation on days more disturbed than 
in the case of all days of a month or year. The general 
transition in the character of the variation from station 
to station is more clearly in evidence than in the case of 
disturbed and quiet days considered separately, but there 
are considerable discrepancies in Z, probably because 
of uncertainties in measurement. 



3. The latitude distributions of the symmetrical and 
sinusoidal parts of the annual variation. --It is of interest 
to know whether the form of AV may change in some im- 
portant respect with year, for instance with year of sun- 
spot-cycle. A to H of Figure 38, giving averages of the 
annual variation for various sets of years of the period 
1905 to 1940, show little evidence of important change 
with year in the annual variation for all days. It is evi- 
dent that the results for the vertical component show 
large and erratic fluctuations which are of questionable 
significance, but the change with latitude in the geomag- 
netic north component is rather clearly defined. A to D 
of Figure 39 show the averages for groups of year near 
sunspot maximum and for groups near sunspot minimum. 
Figure 40 shows that the average amplitude is about 
twice as great for the sunspot maximum groups of years. 
Figure 41 illustrates year by year the close similarity of 
the annual variation at the high-latitude station Sitka 
( $ = 60°) as compared with Cheltenham ($ = 50°.l) for 
each year of the period 1905 to 1936. 

In order to obtain a more accurate derivation of the 
latitude distributions of the symmetrical and sinusoidal 
parts of the "annual variation than would be possible for 
the stations used in deriving the data of C of Figure 37 
for the year 1932-33 (including our only important source 
of polar data), averages were derived for the 12 years of 
the period 1922 to 1933. Data for disturbed days minus 
quiet days are shown in A of Figure 42. The correspond- 
ing symmetrical and sinusoidal parts derived are illus- 
trated in B and C of Figure 42. Results of the same 
type for a longer period of years are given in Figure 43. 
The sinusoidal part was derived by Fourier analysis 
and checked by subtracting (or adding in the case of Z) 
averages for Southern Hemisphere stations from those 
for Northern Hemisphere stations. The symmetrical 
part was then obtained by subtracting the sinusoidal part 
from the total annual variation and checked by adding 
results for Northern Hemisphere and Southern Hemis- 
phere stations. Using the known latitude distribution of 
the daily means of disturbance for international dis- 
turbed days (D mi ) [1] the symmetrical part for each 
station was then reduced to give the equatorial value of 
the symmetrical part mostly closely in correspondence 
with the values at all stations. This equatorial value 
was then finally used in conjunction with the values of 
the latitude factor directly proportional to D m j to obtain 
the illustrated symmetrical part for each station. The 
results showed good agreement with the symmetrical 
part at each station found originally from subtraction of 
the sinusoidal part from the observed annual variation at 
each station, except in the vertical component. In the 
case of the latter component, the symmetrical part was 
checked with that obtained from the geomagnetic north 
component by direct use of the known latitude distribu- 
tions of both the geomagnetic north and vertical compo- 
nents of D m j illustrated in Figure 44, as deduced for 
years 1922 to 1933. 

Of special note is the presence of values notably dif- 
ferent from zero in the geomagnetic east component in 
high latitudes. This seems to be a natural consequence 
of the choice of geomagnetic components instead of com- 
ponents normal to or parallel to the auroral zone. 

Figure 44 gives the latitude distribution of the inter- 
national-disturbed-day means minus quiet -day means, 
averaged for the years 1922 to 1933, except for high 
northern latitudes, for which data for only the Polar Year, 



THE GEOMAGNETIC ANNUAL VARIATION, AV 



95 



1932-33 were used. These were multiplied by the factor 
1.21 (derived from lower latitude stations) in reducing 
them to the mean of 1922 to 1933. Values for stations in 
the range <$ = 60° to 70° have been plotted and adjusted 
in position relative to a circular auroral zone located in 
geomagnetic latitude 67°. 

The geomagnetic north component is negative in sign 
in all latitudes. It attains a minimum value of -61 y at 
the auroral zone, and has a secondary minimum of -25y 
at the equator, about which the field in this component is 
symmetrical. The geomagnetic east component appears 
to be zero in low and middle latitudes. Near and inside 
the auroral zone the field, as before, does not show per- 
fect symmetry relative to the geomagnetic axes. The 
vertical component of D m j has a maximum value of 27y 
just inside the auroral zone, and a minimum of -21 y just 
outside. The vertical component is zero near the equator 
and is opposite in sign on either side of it. We have noted 
previously that Figure 44 gives the latitude distribution 
of the symmetrical part of the annual variation, apart 
from a constant of proportionality, which is the same in 
all latitudes. The latitude distribution appears rathei 
well determined, though the adopted values in polar re- 
gions are of course more uncertain than those for the 
region between the northern and southern auroral zones. 

Figure 45 shows the latitude distributions and time- 
phases found for the geomagnetic north and vertical com- 
ponents of the sinusoidal part of the annual variation. On 
the upper left is shown the variation of the geomagnetic 
north component (X') with latitude as indicated by the 
amplitude (Ci x ) and ( aj x ') of the expression -CjX cos 
(t + aj) = ajcos t + bjsin t where t is the time reckoned 
at the angular rate of 30° per month commencing on Jan- 
uary 1. The data for various years have been reduced to 
the mean of the years 1922 to 1933. 

The values of Cj x , apart from proportional factors 
the same in value for all stations, in each particular mean 
of a group of years, appear to fit rather well a smoothed 
curve drawn by eye among the points. The values Cj X 
are zero (by definition of the X' -component) at the geo- 
magnetic north pole, and go to a maximum roughly half way 
between the pole and the auroral zone, after which they 
decrease rapidly at first then slowly to attain a zero- 
value at the equator, about which the component appears 
roughly symmetrical. The phase angle (aj x ) in the 
Northern Hemisphere is the reverse of that in the South- 
ern Hemisphere. On the lower left-hand side are shown 



the calculated points, from the Fourier^analysis of the 
data, for the corresponding values aj x and bi X , the 
curves drawn being those computed from the adopted 
curves for Ci x ' and aj x ' > giving as should be expected, 
a reasonably good fit of the points for ai x and b} X . 

On the right are shown the corresponding values for 
the vertical component of the sinusoidal part of the an- 
nual variation. The values of CjZ decrease rapidly 
from the pole equatorwards, attaining a fairly constant 
value in middle and low latitudes. The phase angles 
oc jZ are not well determined since there is some con- 
siderable scatter in the points obtained from the data. As 
drawn, there would seem to be indicated a slight but rath- 
er insignificant lead in phase in middle and low latitudes 
relative to the geomagnetic north component. However, 
the curve adopted for aj Z is naturally rough and some- 
what tentative, although the values of aj Z and bj z ap- 
pear on this basis rather successfully fitted, and hence 
lend support to the authenticity of the curve adopted for 



O.' 



Figure 46 indicates the grave difficulties attendant 
on estimating, in terms of the Fourier coefficients -aj, 
bj, the sinusoidal part of the annual variation in a par- 
ticular latitude by individual years. In the case of the 
geomagnetic north component, the scatter of the yearly 
points about the mean (indicated by a vector) is not 
unduly great, and the vectors are determined with fair 
accuracy both in amplitude and phase. In the case of the 
vertical component, the results are clearly erratic both 
in amplitude and phase, and it is evident that the mean of 
37 years is of an accuracy leaving much to be desired. 

The foregoing results were used in deriving Tables 
1-C to 1-F of the previous volume [1]. 

A zonal harmonic analysis was attempted of the Fou- 
rier components of the sinusoidal part of the annual var- 
iation. However, the computed fractions for external 
origin for harmonics of different degrees did not agree 
well with one another. This would suggest that our lati- 
tude distributions for the Fourier coefficients were not 
sufficiently accurate for the purpose. 

The electric current system which could reproduce 
the symmetrical part of AV seems to resemble closely 
that proposed by Chapman [3] for the storm-time varia- 
tion. Due to the sinusoidal part of the annual variation, 
its general form will undergo a considerable seasonal 
variation. 



Table 102. Values of Fourier coefficients of series for sinusoidal 
[Figure 35(C)], annual variation, Polar Year, 1932-33 



iart 



Station 


AG 


Al 


bl 


Thule 


88.0 


+ 


1.73 


+ 


3.98 


-8.34 


joclhavn 


79.8 


- 


.33 


+ 


14.52 


-8.76 


Juliannehaab 


70.8 


+ 


.58 


+ 


.87 


+ .80 


Troroso, Fort Rae, College, Fairbanks 


66.9 




.00 


+ 


.53 


-3.14 


SoJankyla 


63.8 




.00 


+ 


1.70 


-2.96 


Lerwick, Sitka 


61.2 


+ 


.17 


+ 


2.47 


-3.18 


Eskdalemuir, Lovo, Sloutsk 


57.5 


- 


.17 


+ 


1.88 


-3.19 


Rude Skov 


55.8 


- 


.33 


+ 


1.61 


-2.92 


Agincourt, Abinger 


54.5 


- 


.58 


+ 


2.23 


-3.70 


Val Joyeux, Cheltenham 


50.7 


+ 


.83 


+ 


.49 


-4.17 


Tucson 


40.4 




.00 


+ 


.81 


-3.81 


Helwan 


27.2 




.00 


- 


1.97 


-7.68 


Honolulu 


21.1 


+ 


.17 


+ 


.93 


-0.39 


Lukiapang 


20.0 


+ 


.50 


- 


.33 


- .07 


Alibag 


9.5 




.00 


- 


3.46 


-1.18 


Huancayo 


- 0.6 


- 


OH 


+ 


1.61 


+ 2.08 


Pilar 


-29.2 


- 


.75 


- 


4.06 


+ 5.50 


Cape Town 


-32.7 


- 


.17 


- 


3.39 


+ 5.75 


Watheroo 


-41.8 


+ 


.25 


- 


3.68 


+ 2.32 


Toolangi 


-46.7 


+ 


.17 


- 


2.48 


+ 2.16 


Amberley 


-47.7 




.00 


- 


1.31 


+ 4.55 


South Orkneys 


-50.0 


- 


.08 


+ 


.19 


+ 5.01 



96 



FIGURES 35-46 



Figure Page 

35(A)-(B). Monthly mean departures from annual means of magnetic intensity for geomag- 
netic north, east, and vertical components 98 

3j>(C). Variation with geomagnetic latitude of monthly mean departures 100 

36. Monthly means minus annual means, 1932-33 101 

37(A)-(C). Monthly mean departures from annual means, geomagnetic components X', Y', and 

Z, quiet days, disturbed days, and disturbed minus quiet days, Polar Year, 1932-33 .... 102 
38(A)-(H). Monthly mean departures from annual means, geomagnetic components X', Y', and 

Z, various groups of years 105 

39(A)-(D). Monthly mean departures from annual means, geomagnetic components X', Y', and 
Z, sunspot minimum years 1912-14 and 1922-24, and sunspot maximum years, 1916-18 
and 1927-29 110 

40. Monthly mean departures from annual means, sunspot minimum years 1912-14 and 

1922-24, and sunspot maximum years 1916-18 and 1927-29 112 

41. Successive overlapping five-year averages of monthly mean departures from annual 

means, Sitka, 1907-37, and Cheltenham, 1902-40 112 

42(A)-(C). Disturbed minus quiet day means (D m i), X'-, Y'-, and Z -components, 1922-23 ... 113 

43. Monthly mean departures from annual means in geomagnetic X'-component, 1911-35 . . . 116 

44. Variation with geomagnetic latitude of X'-, Y'-, and Z-components of D m i, mean of 

1922-33 116 

45. Variation with latitude of sinusoidal part of annual variation, all days, in geomagnetic 
north and vertical components, various groups of years 1905-41, reduced to mean of 

1922-33 117 

46. Harmonic dials for average sinusoidal part of annual variation, mean of values for 

various observatories, 1905-41 118 



97 



THULE 

Its. o, o%) 



GODHAVN 

(7»%, 32T5) 



SVEAGRUVAN 
(73%, 130't) 



CALM BAY 
(71%, 153%) 



chesterfield inlet 
(73%, 324% j 



SCORESBY SUND 

(75%, ai%) 



BEAR ISLAND 
(7I°I , I24%J 



POINT BARROW 
(66%, 24 1?!) 



JULIANNEHAAB 
(70%, 35%) 



FORT RAE 
(69%, 290%) 



UATOTCHKIN SHAR 
(64%, 146%) 



DICKSON 
(63%, 161%) 



TROUSO 

(67°l, 116.7) 



COL LEGE-FAIRBANKS 
(64%, 255°4) 



PE TSAUO 

(64%, 125%) 



SODANKYLA 
(63%, 120%) 



MEANOOK 

(61%, 301%) 



LERWICK 

(62'. 'S, 86%) 



SITKA 

(60%, 27S°4) 



ESKDALEMUIR 
(SB%, 62%) 



LOVO 

(S6°l , 105%) 



SLOUTSK 
(56%, 117%) 



RUDE SKOV 

(ss%, >a?3) 



AGINCOURT 
(}S%, 347$)) 



ABINGER 
(S4% , 83%) 



DC BIL T 
(53%, 69%) 



MANMAY 

(52%, Si't J 



VAL JOYCUX 
(51%, B4%) 






^. 



Zk 




I I I ' ' 




L_i_ 



FIG 3S/A)-M0NTHLV MEAN DEPARTURES FROM ANNUAL MEANS OF MAGNETIC INTENSITY- FOR GEOMAGNETIC NORTH 
fax') EAST far') AND VERTICAL t/Ut) COMPONENTS AT VARIOUS OBSERVATORIES, SEPTEMBER 1932 TO AUGUST 1933 
(GEOMAGNETIC LATITUDES AND LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 



98 




FIG 35<B)-MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS OF MAGNETIC INTENSITY FOR GEOMAGNETIC NORTH 
fax'), EAST (AY'), AND VERTICAL fez) COMPONENTS AT VARIOUS OBSERVATORIES, SEPTEMBER 1932 TO AUGUST 1933 
(GEOMAGNETIC LATITUDES AND LONGITUDES INDICATED RESPECTIVELY IN PARENTh 7£sj 



99 







FIG3S(C)-VARIATI0N WITH GEOMAGNETIC LATITUDE OF MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS OF GEO- 
MAGNETIC COMPONENTS OF INTENSITY, SEPTEMBER 1932 TO AUGUST 1933 (GEOMAGNETIC LATITUDES INDICATED 

IN PARENTHESES) 



100 



THULE 
(S8?0) 



GODHAVN 
{79%) 



JULIANNEHAAB 
(70?8) 



TROMSO, FORT RAE , 
AND COLLEGE-FAIRBANKS 
(66°9) 



SODANKYL ' 
(63°8) 



LERWICK AND SlTKA 
fff/?*J 



ESKDALEMUlR, LOVQ, 
AND SIOUTSK 
(57?S) 



RUDE SKOV 
(55°8) 



AGiNCOURT AND 
ABtNGER 
(54?S) 



VAL JOYEUX AND 
CHEL TENHAM 
(S0?7) 



TUCSOU 
(*0°4) 



HE L WAN 



HONOLULU 



LUK1APANG 
(20*0) 



ALiBAG 
(9?S) 



HUANCAYO 
(-0°6) 



PILAR 
(-30°!) 



CAPE TOWN 



WATHEROO 



TOOL ANGI 



4MB E PL E Y 
(-47°7) 



SOUTH ORKNEYS 

(-so'.o) 







_l I I — I — 1 1 L 





EQUATORIAL VALUE X FACTOR 






4x'-(EQUAT0RIAL VALUE X FACTOR) 



_!__! I I I I I— L 



FIG36-MONTHLY MEANS MINUS ANNUAL MEANS, 1932-33, OF GEOMAGNETIC NORTH COMPONENT (x') WITH EST/MATEO 
PART SYMMETRICAL ABOUT GEOMAGNETIC EQUATOR, AND SEASONAL PART FITTED WITH FOURIER TERM (3 + 3, SINX 
+ b COS x) SHOWN DOTTED, WHERE X IS AN ANGULAR REPRESENTATION OF TIME AT THE RATE OF 30 PER MONTH 
BEGINNING SEPTEMBER I, 1932 (GEOMAGNETIC LATITUDES INOICATEO IN PARENTHESES) 



101 






THULE 

(aa%) 



GODHAYN 



JULIANNEHAAB 
(70°e) 



TROMSO, FORT RAF , 
AND COLLEGE-FAIRBANKS 
(66%) 



SODANKYL* 



LERWICK AND SITKA 

(si?z) 



(sA) 

RUDE SKOV 
(55°S) 



( S 4?S) 

VAL JOYEUX AND 
CH£L TENHAM 
(S0?7) 

TUCSON 
(40%) 



HEL WAN 



HONOLULU 



LUKIAPAN6 
(<0°0) 



ALIBAG 
(9?S) 



HUANCAYO 

(-o°«) 



PILAR 



CAPE TOWN 



WATHEROO 



TOOLANCI 



AUBERLEY 



SOUTH ORKNEYS 

(-so°o) 



SONDJFUAUJJA 






AX 

_l I L_ 



SONDJFUAUJJA 



ay 1 

_J I 1 I I L 



SONDJFUAUJJA 







FIG37M-M0NTHLY MEAN DEPARTURES FROM ANNUAL MEANS, GEOMAGNETIC COMPONENTS x\ Y 1 , AND Z, QUIET 
DAYS, POLAR YEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



102 



THULE 

($a'o) 



GODHAVN 
(7»U) 



JULIANNEHAAB 
{70%) 



TROMSO, FOPT PAE , 
AND COLLEGE-FAIRBANKS 



(et?9) 

SODANKYLA 
(6J°S) 



LERWICK AND SITKA 

(eih) 



ESKDALEMUIR, LOVO, 
AND SLOUTSK 



(S7.'S) 

PUDE SKOY 
(55°S) 



AGINCOURT AND 
ABINGER 
( S 4?S) 

YAL JOYEUX AND 
CHEL TENHAM 
(50°7) 



TUCSON 
(40?A) 



HEL WAN 
(I7?i) 



HONOLULU 
(21°,) 



LUK/APANG 

(?o?o) 



ALIBAC 



HUANCAYO 

(-o?e) 



PILAR 



CAPE TOWN 
(-3!?7) 



WAT HE POO 
(-41%) 



TOO LANG I 
(-46°7) 



AMBERLEY 
(-47°7) 



SOUTH ORKNEYS 
(-S0?0) 





. A 



^Wv^/S, 






_i i i i i — i — i — i — i-L 





"V 



■ * - ^ 




v. .— ^_ 




J I I I 1 I I I I I — u 



FIG.3T(B)-M0NTHLY MEAN DEPARTURES FROM ANNUAL MEANS, GEOMAGNETIC COMPONENTS X', Y', AND Z, DISTURBED 
DAYS, POLAR YEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



103 







HELWAr\ 



HONOLULU 

(a,?,) 



LUKIAPANG 
(20°0) 



AL IB AG 

( 9 ?s) 



HUANCAYO 

(-o'e) 



PILAR 



CAPE TOWN 
(-32??) 



WATHEROO 



TOOLANGI 



^A -. ^ . A 



SOHOjrvA/UJ 




NP^ 



■^r- — -^ - ■w ■ 



■ »»■»' * w ' m 

■ « « — «■,,-»■■«■■ 

> ■ _ t , — , L _ , — ^ 





FIG. 37(c)- MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS, GEOMAGNETIC COMPONENTS x\ y', AND Z , DISTURBED 
MINUS QUltT DAYS, POLAR YEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



104 




F IG.38(A) AND (B)- MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS, GEOMAGNETIC COMPONENTS r' Y f , AND Z, 
VARIOUS GROUPS OF YEARS (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



105 




FIG.38(C)AND(D)- MONTHLY mean departures from annual means, geomagnetic COMPONENTS X, Y, AND 
VARIOUS GROUPS OF YEARS (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



106 




HELWAN 
(tTh) 



HONOLULU 

("°0 



AL IB AC 



WATHEROO 



CHRISTCHURCH 
(-4B°b) 



to 

1926-30 

SODANKYLA 

(s3°e) 



LERWICK 



SITKA 

(eo?o) 



ESKDALEMUIR 

(se?s) 



SLOUTSK 
(S6°b) 



RUDE SKOY 

(ss's) 



ACINCOURT 

(ss?o) 



ABINCER 



VAL JOYEUX 
(Sl'j) 



CHEL TENHAM 

(so?,) 



TUCSON 



MEL WAN 
HONOLULU 



4 1 1 1 1 1 1 1 1 1 1 t- 




-I 1 1 1 1 1 1 4 1 1 1 1- 



-y ■ ■ + ■ -. 



^ » I ■ « 



JK' 



H 1 4 1 1 1 1 1 1 1 1 N 





FIG.3B(D)anD(E)- MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS, GEOMAGNETIC COMPONENTS X, Y, AND Z, 
VARIOUS GROUPS OF YEARS (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



107 




FIG.38(£)AND(f)— MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS, GEOMAGNE TIC COMPONENTS X, Y , AND Z, 
VARIOUS GROUPS OF YEARS (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



108 



(6) 
1936-40 

CHEL TENHAM 
(50',) 



TUCSON 
(40U) 



HONOLULU 



HUANCAYO 

(-o%) 




H 1 1 1 1 1 1— I 1 1 1 r 



-I 1 1 1 — l 1 1 — | 1 1 1 — r 

JFMAMJJA S O N D 



■i 1 1 1 1 1 1 1 1 1 1 r 



i — i — i — i — i — I — i — i — i — i — r . 

JFMAUJJASONO 




(») 
1911-35 
SITKA 
(60%) 



ESKOALEMUIK 
(58°5) 



RUDE SKOV 



(-»••«; 



ABINCEK 
(54%) 



YAL JOYEUX 
(5,%) 



CHELTENHAM 
(50°!) 



TUCSON 
(40%) 



HE L WAN 



HONOLULU 



ALIBAC (24 YEARS) 

(A) 






j i i i i i i i i_ 



i i i — i — 1_ 



FIG.38(G)AND (H)- MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS, GEOMAGNETIC 
VARIOUS GROUPS OF YEARS (GEOMAGNETIC LATITUDES INDICATED 



components x\ y', and z, 
in parentheses) 



109 



w 

1912-14 



SITKA 

(toTo) 



ESKDALEMUIB 



DUDE SKOV 

(ssU) 



GREENWICH 



VAL JOrEUx 
(s,°3) 



CHEL TENHAM 

(so°i) 



TUCSOU 
(40°.) 



HE L WAN 



HONOL UL U 



ALIBAO 
(9°S) 




'h-A — I — I — I — I — I — I — I — H 



JfUAUJJA S N 



■ » » ■ ■ 




H — I 1 — I 1 — I — I — h 




+-H — l — I— I — I — l — I — l — I — I — h 



(B) 

1922-24 



SITKA 
(60°0) 



E SKOAL EMUIR 
(saTs) 



RUDE SKOV 

(ss'a) 



ABINGCR 
(S4°0) 



VAL JOYEUX 

(Slh) 



CHEL TENHAM 

(so',) 



TUCSON 

(4*4) 



MEL WAN 



HONOLULU 



ALIBAO 




-■ » ■ J 



1 ■ ■ I I I I I I l—l L 




J I I I L 



FIG. 39(A) AH/0 (B) — MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS, GEOMAGNETIC COMPONENTS x', y', AND Z; 
SUNSPOT MINIMUM YEARS: (A) I9I2-/4 , (8j 1922-24 (GEOMAGNETIC LATITUDES INOICATED IN PARENTHESES) 



110 




FIG.39(C)AND(D)— MONTHLY MEAN DEPARTURES PROM ANNUAL MEANS, GEOMAGNETIC COMPONENTS x', v', AND Z ; 
SUNSPOT MAXIMUM YEARS: (C) 1916- 18 , (oj 1927 -29 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



111 




FIG. 40 -MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS, GEOMAGNETIC COMPOMPONENT AX', SUN- 
SPOT MINIMUM (1912-14, 1922-34) AND MAXIMUM (1916-18, 1927-29) YEARS (GEOMAGNETIC LATITUDES 

INDICATED IN PARENTHESES) 









y\ 


y\. 


A . 


1910 

.A A 


. A (* 


, A / 


s rv a 


^/\ A 


/S/5 


\A , 




V 




1920 


nA ' 


V V 




v v 
A - 


A n 


^ V 


A 


.A/ 


yA; 


v V 

/9J0 

vA , 


YV 
■A 


vA ; 


^ v 

k A ; 




v y*jv V 

>9J5 

k A A 


v V 


v V 


v v 


v V 


v V 


v V 


v V 


v V 


v/ VJ 












fa/ 5-/ 7- 


/m 




A 


1905 

A J A 


A, 


y\> 


A 


1910 

An 


A/s 


- A ys 


^/*\ A 




/ v 

1915 


„n 






* V 


^ V 

1920 

-\A J 


^A - 






v \yi 


A ,-LA a 


N If 

A 


V V" 


A , 


1930 


A j A 


AT 


A 


1935 

A A 




* V 


v v 


v V 


v u^ 


v \^ 


•/ ^ 


J \\ 




y w 








fej c#«r 


ENHAM 





FIG. 4-1 -SUCCESSIVE OVERLAPPING FIVE-YEAR AVERAGES OF MONTHLY MEAN DEPARTURES FROM 
ANNUAL MEANS, (a) SITKA, 1907-37, AND (8) CHELTENHAM, 1902-40 



112 




FIG.42(A)- DISTURBED MINUS QUIET DAY MEANS ( D m; ), X-, Y-, AND Z-COMPONENTS, MEAN OF 1922-33 (GEOMAG- 
NETIC LATITUDES INDICATED IN PARENTHESES) 



113 



SOOANKVLA 



SITKA 

(eo?o) 



LERWICK 



ESKDALEMU'R 

(se°s) 



RUDE SKOV 

(ss?s) 



AG IN COURT 

(ss'o) 



AB1NCER 
(S4?0) 



DE BILT 
(S3?S) 



VAL JOrEUX 
(„? 3 ) 



CHELTENHAM 

(so?,) 



TUCSON 
(4C?4j 



HONOLULU 



AL IB AC 
(,°S) 



(*>) 



NUANCAYO 



WATHEROO 



AUBCRLEY 




S O N O 




* ■ ■ ■ ■ "-^- 




Va/^/ 



N */\f 



J I I 1 1 1 L. 



.■ ■ ■ ■t ill 



* * i i - — w m 



t ■ ■ i i 



■ | ■ mtmmfmMjmmttmm^m m ■ ■ 



»•»■■•■«•■■ 



• < ■••>»<»att 



• •■•»••>■■■• 



■ ■ ■ ^^^^^^"^^^^i • ■ 



AY' 4Z 

• i ■ I ' ' ' I i l ill l l l t- 




■ ■■■»■■■■««» 



FIG. 420)- PART OF D mi SYMMETRICAL ABOUT EQUATOR, X-, Y-, AND Z-COMPONENTS, MEAN OF 1922-33 (GEOMAG- 
NETIC LATITUDES INDICATED IN PARENTHESES) 



114 



SODANKYLA 



SITKA 

(to'o) 



LCRWICK 



£ SKOAL CULM) 

(s*?s) 



RUDE SKOV 

(ss°.) 



ACINCOURT 

(ss?oJ 



ABlNGER 
(S4?o) 



OC BUT 
(S3?.) 



VAL JOYEUX 



CHELTENHAM 

(so?,) 



TUCSON 
(40°,) 



HONOL UL U 



ALIBAO 
(,?3) 



UANIL A 
(J°J) 



HUANCAYO 
(-0'6) 



WATHEROO 



AUBERLEr 



.»»■■■ 



■♦ii^^ I ■ 



J l l I l l l I l i i_ 



T 1 1 1 1- 



-1 p 1 r 



JFUAUJJASONO 




■ ■«»■« 



« * 



■ ■»■■■■* 



r* 1 I «- 



' ' ' ' ' 1—1 1 1 III I 



_l I I I L 



FIG. 4Zp)- SINUSOIDAL PART OF D mi ANTI-SYMMETRICAL ABOUT EQUATOR, X-, K-, AND Z-COMPONENTS, MEAN OF 
1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



115 






SITKA 
(60%) 



ESKDALEMUIR 

(ss°s) 



RUDE SKOV 

(ss°s) 



VAL JOYEUX 
(Sl?j) 



CHEL TCF 
(50?,) 



TUCSON 
(40°4) 



HONOL UL U 



AC I BAG 



JFMAMJJA S O N D J 




(A) 



"i 1 1 1 ' 1 1 1 1 — i IT! 1 1 1 1 1 1 1 1 1 1 r- 

F U A M J J A SON DJFUAMJJA S O N 




AX -AX C 



(B) 




_1 I I I I L 



(c) 



FIG. 4-3— (A) MONTHLY MEAN DEPARTURES FROM ANNUAL MEANS IN GEOMAGNETIC x'-COMPONENT, (B) PART SYM- 
METRICAL ABOUT EQUATOR, AND (C) SINUSOIDAL PART, 1911-35 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 




FIG. 44 -VARIATION WITH GEOMAGNETIC LATITUDE OF X L , Y-, AND Z-COMPONENTS OF D mi) MEAN OF 1922-33 



116 




FIG. 4-5- VARIATION WITH LATITUDE OF SINUSOIDAL PART -C, COS (t+Ot,)= 9/ COS t + b, SIN t OF ANNUAL VARIATION, 
ALL DArS, IN GEOMAGNETIC NORTH (x'J AND VERTICAL (z) COMPONENTS, VARIOUS GROUPS OF YEARS I90S-4I, RE- 
DUCED TO MEAN OF 1922-33 



117 



GEOMAGNETIC NORTH COMPONENT 



FIG. 46— HARMONIC DIALS FOR AVERAGE 
SINUSOIDAL PART OF ANNUAL VARIATION, 
MEAN OF VALUES FOR ESKOALEMUIR, 
RUDE SKOV, AGINCOURT, VAL JOYEUX, 
POTSDAM, AND CHELTENHAM (MEAN 
$-S3?S), 1905-41 



SCALE IN GAMMAS 



GEOMAGNETIC VERTICAL COMPONENT 



118 



CHAPTER VI 



THE GEOMAGNETIC POST -PERTURBATION, P 



1. General remarks. --It has been noted that the 
monthly mean values of the geomagnetic field undergo 
changes due to the variation of average geomagnetic dis- 
turbance with season. In the same way, the daily means 
are affected by disturbance on individual days. This ef- 
fect in most latitudes is pronounced decrease in H at 
times of disturbance. 

The value of H increases above the monthly average 
on quiet days. A and B of Figure 47 give the effect of 
post-perturbation as shown by the daily mean departures 
from the monthly mean during a period of disturbance 
and of recovery, May 1 and 2, 1933, for the X'-, Y'-, and 
Z -components of intensity. The X' -component is re- 
duced below the monthly mean during the disturbed pe- 
riod and later rises during the period of recovery, 
throughout the region from pole to equator. The depar- 
tures in X' are large inside the auroral zone, are larg- 
est and most irregular near this zone, and then decrease 
with decreasing latitude. In Y' the changes are relative- 
ly smaller in all latitudes. In Z the departures near the 
center of the northern auroral zone are large and become 
smaller in lower latitudes, with reversal of sign in the 
Southern Hemisphere. 

The consistency in values from observatory to ob- 
servatory is marked, and the post-perturbation is evi- 
dently fairly well determined by only two or three ob- 
servatories if the latitude distribution is known. 

2. The latitude distribution of the post-perturbation . 
P^- -Figure 48 shows the latitude distribution of P, the 
daily means minus the monthly means for a number of 
days of the Polar Year, 1932-33. On September 17, 1932, 
the value of H was about 25 gammas above the monthly 
mean in low latitudes. On December 17, 1932, it was 
about 25 gammas below. Evidently field-observations, if 
made on two such days about five years apart, would give 
a total apparent and fictitious change in the Earth's per- 
manent field of 50 gammas, seriously affecting the esti- 
mate of secular change in H. It is particularly to be 
noted in Figure 48 that the stations, although differing 
widely in their longitudes, exhibit on the whole rather 
good agreement with each other, except possibly near 
the auroral zone, where considerable irregularity ap- 
pears. In general, it appears that any longitude effect 

in P can be neglected in most applications. In fact, the 
mean departures derived for two or three stations suf- 
fice approximately to estimate these departures at all 
other stations, when the latitude distribution appropriate 
to each month of the year is also known. 

The average latitude distribution of the daily means 
minus monthly means can be obtained by averaging such 
values for a sufficient number of years by months. As a 
good approximation, we may take the values D m j, the val- 
ues for disturbed days minus quiet days by months, since 
the all-day minus quiet-day means are small. 

A of Figure 49 gives the latitude distribution of D m j 
by months as derived for the average of the years 1922 
to 1933. Values for the Polar Year, 1932-33, reduced tc 
1922 to 1933, are included to give a rough indication of 
the latitude distribution in polar regions. 



The change from month to month is largest in high 
latitudes due to the presence of a sinusoidal annual term 
of considerable magnitude in the X'- and Z -components. 
The Y' -component is very small and nearly zero in all 
months. 

From the latitude distributions of A and B of Figure 
49, average monthly proportionality factors for various 
latitudes can be derived which, when multiplied by the 
known daily mean departure from the monthly mean in a 
particular latitude, yield an estimate of the correspond- 
ing value in any other latitude. With this purpose in mind, 
the daily mean departures (on 75th meridian time) from 
the monthly mean of the H -component for Cheltenham 
($ = 50°.l) and San Juan (<$ = 29°.9) were meaned for 
each day of the period 1905 to 1942 and tabulated for 
presentation as Table 1-G of the preceding volume [1]. 
The corresponding proportionality factors, by months, 
for each two degrees of geomagnetic latitude were given 
in Tables 1-H and 1-1 of the same volume. A correction 
for secular change in H was neglected. 

In a number of cases, data for either Cheltenham, 
San Juan, or both were missing. In such cases, values 
for other low -latitude stations were substituted, also on 
a 75th meridian time basis, reduced by the known aver- 
age latitude distribution of D m j to a mean assumed ap- 
propriate to that of Cheltenham and San Juan. Such sub- 
stitutions are indicated by appropriate footnotes. 

It was also found on occasion that the values for 
Cheltenham and San Juan sometimes differed by more 
than ten gammas. In this event, a value was taken from 
a third station, on 75th meridian time, reduced to the 
mean of Cheltenham and San Juan. The three values were 
then compared and a mean was taken either of all three 
values, or of two of the three depending upon the values. 
If two values agreed well but the third showed marked 
disagreement (in excess of ten gammas difference from 
either value for the other two), it was assumed that the 
third value was defective. On a few occasions, there 
were several successive days for which values for Chel- 
tenham and San Juan disagreed by more than ten gammas, 
as if there might have been changes in base-line values 
during the month. A third station, it was thought, per- 
mitted a more accurate choice of value in such cases. 
The third station usually used was Tucson, 1905 to 1910, 
Manila, 1931 to 1938, or Watheroo, 1939 to 1941. 

The daily mean departures from the monthly means 
at various stations were, where necessary, multiplied by 
appropriate factors given from the latitude distribution 
for D m j, in estimating values for the mean of Chelten- 
ham and San Juan. The following multiplicative factors 
were adopted: Cheltenham, 1.1; Tucson, 1.0; San Juan, 
0.9; Honolulu, 0.8; Manila, 0.7; Alibag, 0.7; Huancayo, 
0.7; and Watheroo, 1.0. 

Even in low and middle latitudes, where disturbances 
are less marked than in polar regions, it was sometimes 
found that the values at three stations differed greatly 
from one another, and the discrepancies in P on such 
days would then be found erratic at many stations. Val- 
ues given by the mean of P at San Juan, Cheltenham, and 



119 



120 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



a third station, were in any case entered in Table 1-G fl], 
with a suffix s indicating considerable magnetic disturb- 
ance or storm. As unusual and erratic examples of the 
results for San Juan, Cheltenham, and a third station, 



respectively, the following values of P in gammas were 
noted: July 8, 1928, -66, -55, and -131; January 25, 1938, 
-77, +6, and -70; April 24, 1939, -43, +2, -43; July 5, 
1941, -130, -227, and -213. 



FIGURES 47-49 



Figure Page 

47(A)-(B). Daily means minus monthly means of May, 1933, for geomagnetic north, east, 

and vertical components, magnetic storm of May 1, 1933 122 

48. Change with geomagnetic latitude of departures of daily means from monthly means at 

magnetic observatories 125 

49(A)- (B). Latitude distribution of average monthly disturbance, disturbed minus quiet days 

and all days, 1922-33, values for Polar Year, 1932-33, reduced to 1922-33 126 



121 



30 

APR 



THULE 

(ae°o) 



GODHAVN 



SCORESBY SUNO 



SVEAGRUVAN 



CHESTERFIELD INLET 
(73?S) 



BEAR ISLAND 
(7I°I) 



JUL IANNEHAAB 
(70°8) 



FORT RAE 
(69°0) 



POINT BARROW 
(6S°6) 



TROMSO 
{67° I) 



PE TSAMO 
(64°9) 



COLLEGE FAIRBANKS 
(S4°SI 



SODANKYLA 
(6J°S) 



LERWICK 
(6?°5) 



MEANOOK 

(e/'e) 



SITKA 
(60°0) 



ESKOAL EMUIR 

(s£s) 



LOVO 

tse'i) 



SLOUTSK 

(se'o) 



RUDE SKOV 

(sirs) 



AGINCOURT 



ABINGER 
(SA-O) 






\^- 



T * T T T 




A. 





A^ 




^ — - 




FIG. 47(Ay- DAILY MEANS minus monthly MEAN OF MAY 1933 FOR geomagnetic north (ax 1 ), east (ay'), and VERTICAL 

{az) components, magnetic storm OF MAY 1,1933, AND days following, AT VARIOUS OBSERVATORIES, APRIL 30 TO 

MAY 13,1933 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



122 




FIG.4-7(B>- DAILY MEANS MINUS MONTHLY MEAN OF MAY 1933 FOR GEOMAGNETIC NORTH (&X'), EAST faY'J AND VERTICAL 

(HZ) COMPONENTS, MAGNETIC STORM OF MAY 1,1933, AND DAYS FOLLOWING, AT VARIOUS OBSERVATORIES, APRIL 30 TO 

MAY 13,1933 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



123 





80°' 60°' 


*?° £o* ' 6" ' 


— I- ~ T ' " T V 1 
-*>0 -40 


80° 60° 40° 20° 0° -20° 
GEOMAGNETIC LATITUDE 


-40°' 


80° ' 60°' 40° 


' i>b° ' 


° ' -^0° ' -40° ' 


SEPTEMBER 17, 1932 


••\°" 


% "* 


•• • • .*. 


• -•- • . 




■/■,. 




• . •' 












."•* • 






OC TOBER 9, 1932 


•\lft-" 


i '. ' ' 


• • ■ " ■ s 


.. 




. 






1 










*!"•*/ ■ 


• 




NOVEMBER 10, 1932 
DECEMBER 17, 1932 


• -V*' 


„• • ' " • 


■' . • • »■ 


•-Vm. 




. . «.. 






.» 










'° vm 4: • 


* 




•i . 


"*•«.■■■ 


. N 


•"» .«t* ■ °° ° ' ,. " 


° * 


« •••; 




1 * " •> 




« 


















• 






• • 




• 






JANUARY 8, 1933 


• . ••wt** 


. •• •* . . 


\. . • r 


i • . .' . 






* 


. • '. 








" 






' 






• 










•/ 














■ 




■ 






FEBRUARY 23, 1933 












. .#-r 






" • • .'** 


■" ■ 


• ■ % 


s 




",*■ 




• 




S 






• 










MARCH 27, 1933 
APRIL IB, 1933 


m 1 ■ 






• - J.- • \ 




* 










• 






• •• • 






* ' ".* 


/ " '" 


.• ' ■/ 


. •_.y-™* ■ ■ "■ **• « 




' ii* 




' 




















MAY 16,1933 


;; . 






' ■ "-* T\ ■ ' 




. . , 


. 














. o** 


• 




JUNE 5, 1933 
JULY 9, 1933 


-■^A** 




•» 








• 






















• * ' ' • ' 


"• " * "" 






'J*** 


. » 


• 




-•. 












• 






^ 




. 






• 






AUGUST 31, 1933 


v - F 


• .• \ ." • 


•" it • * 


• *ry • % - • '- 




• •..•■ 


• 


*- • - .a 


i iiii 


ax' 
■ i i i • i 


• •■I 


AY' 




V** 


'■ * • * 

62 





FIG.4B- CHANGE WITH GEOMAGNETIC LATITUDE OF DEPARTURES OF DAILY MEANS FROM MONTHLY MEANS AT MAGNETIC OBSER- 
VATORIES (TO AVOID CONFUSION, POINTS ON DATES ARE INDICATED ALTERNATELY BY SQUARES AND CIRCLES) 



125 



90° 60° 30° 0° -30° -60° -90 



SEPTEMBER 



NOVEMBER 



o 






90 60 30 -30 -60 -90 

GEOGRAPHIC LATITUDE 



90° 60° 30° if -30° -60° -gS 



A/ 



^X- 



S\^» ■ 




■^ 



^ 




n a sj» t' 



X~ 




FlG.49<A)-LATITUDE-DISTRIBUTI0N Of AVERAGE MONTHLY DISTURBANCE. DISTURBED MINUS QUIET DAYS, 1922-33, YALUES FOR POLAR YEAR, 1932-33. 

REDUCED TO 1922-33 

LEGEND: *'S7ATI0NS,I922-33,B'STATI0NS, l932-33i fLERtVlCK, 1926-13, DUDE SfOY, 1927-33, VAl JOYEUX, HONOLULU, Ar.0 AMBEPlEy, 1923-33 



126 



t — i — n — i — i~~i — i — i — ' — ' — ' — ' — i i ' — i 

60° 30° 0° -30° -60° 

GEOGRAPHIC LATITUDE 



. -I — i — i — i — l — i — l — i — l — i — i — i — l — i — l — i — r. 
0° 60° 30° 0° -30° -60° -SO 



1 — l l I I — i — l — l — i — l — I l l — l l I l 
Xf 60° 30° 0° -30° -60° 



SEPTEMBER 



\y^ 



\jT~ 



vy* 



fzp** 



w~- 



\y^ 



\7= 



-90° 90' 



\J— 



v_ rf ^— . 



•w^- • ■■ ^\7 



-9890' 



^ 



^^ 7 - 



**^ ,. . 



a t ■-f" i > 



=V- 



=\»~ 






M^f 



B - n ~'\ i y»' ■ 



=V 









O 



r/C49(Bj- LATITUDE -DISTRIBUTION OF AVERAGE MONTHLY DISTURBANCE, DISTURBED MINUS ALL DAYS, 1922- 33, VALUES FOR POLAR YEAR, 1932-33, 

REDUCED TO 1922-33 

LEGEND' ••STATIONS, 822-331 B-STATIONS, 1932-33; '-LERHIOX, 1926-33, RUDE SXOV, 1927-33, VAL JOYEUX, HONOLULU, AND AMBERLCY, 1923-33 



127 



CHAPTER VII 



THE SOLAR DAILY VARIATION ON QUIET DAYS, S q 



1. Previous studies of S q. and scope of present work. 
--The solar daily variation has been studied extensive- 
ly by many writers. Schuster [24] established its origin 
as external to the Earth, by the application of the method 
of spherical harmonic analysis. His studies were later 
elaborated on and greatly extended by Chapman [3, 25] 
who derived Sq by seasons and year for the sunspot min- 
imum year, 1902, and the sunspot maximum year, 1905, 
using many stations. The latitude distribution of Sq was 
established with considerable completeness. A more 
careful spherical harmonic analysis was made and a 
dynamo -theory of its origin was developed, based on air 
motions of the upper atmosphere and solar ultraviolet 
radiation. McNish [26] derived and discussed results 
showing a variation in Sq with longitude, using in his 
analysis the anomalously large values of Sq at Huancayo 
and from data on solar -flare disturbances, he established 
the close dependence of Sq on the intensity of solar ul- 
traviolet radiation. A further description of the varia- 
tion of Sq with longitude recently has been given in more 
detail by Benkova [27], based on data for the summer 
season of the Polar Year, 1932-33, the variation of Sq 
with longitude being expressed analytically in terms of 
spherical harmonics. 

It is the purpose here to obtain a description of Sq 
from a considerably greater volume of data, permitting 
estimates of Sq on a world-wide scale for all days of the 
period 1905 to 1942. Account is taken of the consider- 
able change in amplitude of Sq with sunspot cycle [3], 
with month of year, and with day of year. Estimatesuse- 
ful for most days of magnetic storm are also provided. 
The change in Sq with longitude is taken into account, 
although the data available for this purpose are in sever- 
al respects inadequate in many ocean areas. 

2. The solar daily variation on international quiet 
days, by seasons and year, Polar Year, 1932-33 . - -Dur - 
ing the Polar Year, 1932-33, a comparatively large num- 
ber of observatories operated, especially in polar regions, 
and there were additional stations operating also in low 
and middle latitudes. That year was near sunspot mini- 
mum and hence less influenced by disturbances which al- 
ways appear to some degree even on the five most mag- 
netically quiet davs in each month. The data.of this par- 
ticular year hence afford especially valuable material 
for the delineation of the latitude and longitude distribu- 
tion of Sq. 

In high latitudes there is considerable disturbance 
present even on international quiet days. A certain pro- 
portion of this disturbance is present also in low latitudes. 
However, the irregular features of disturbance, because 
of their smaller magnitudes in low as compared with 
high latitudes, tend to cancel out in the average of many 
days. In order that Sq may be determined in high lati- 
tudes, a sufficient number of days of very low magnetic 
activity (low character -figure) are necessary though in 
a few instances successful use has been made of quiet 
hours rather than days. In the present treatment, a 
choice of data on this basis has not been made, although 
the material for this purpose is partially available. 



Some of the results indicate, in so far as international 
quiet days are concerned, the importance of disturbance 
in high latitudes even on quiet days. Data were used for 
all stations for which they were available among those 
listed in Table 103. 

Figures 50 to 53 show the observed average daily 
variations found for many stations, in the geomagnetic 
north (X'-), east (Y'-), and vertical (Z-) components, 
first by seasons separately, and finally, averaged for 
the entire year; Figure 53(C) gives inhomogeneous data 
for the year at high latitude stations. It will be noted 
that the sign of the variation in X' is the same north and 
south of the equator, with reversal near latitudes 30° 
north and south. The variations in Y' and Z are oppo- 
site in sign on either side of the equator. 

Although there is notable similarity in the form of 
the curves for stations in similar latitudes, there is evi- 
dence of a variation of the amplitude of Sq with longitude. 
At Huancayo, as has been noted by McNish [18], the am- 
plitude in the north component is considerably greater 
than at other stations. On close examination it appears 
that this is also the case at Manila, a station likewise in 
a region where the geomagnetic and geographic equators 
diverge widely from each other. With these two excep- 
tions, which are of course accompanied by transitional 
changes in the intervening regions of the equatorial belt, 
the asymmetry in longitude appears slight and secondary 
in importance to the more notable close dependence on 
geographic (or geomagnetic) latitude and local time. 

The world-wide distribution of Sq, as previously 
noted by Chapman for the years 1902 and 1905, shows 
appreciable change with season in amplitude and to some 
extent also in form, especially in regions of transition 
where changes in sign of the components appear. Figures 
50 and 52 show that in general the amplitude is greater 
in local summer than in winter. Figures 51 and 53 indi- 
cate that Sq at the equinoxes closely resembles its year- 
ly average, both in amplitude and phase. 

3. The solar daily variation on international quiet 
davs. by months, seasons, and year. 1922 to 1933. --Fig- 
ures 50 to 53 indicated considerable change in S q with 
season, and it is evident that averaging the quiet days 
into three divisions or intervals representing the sea- 
sons does not provide either accurate or convenient basis 
for interpolation to give values of Sq typical of each month. 
Furthermore, it has been mentioned^ that Sq shows con- 
siderable daily variability [28], and hence the mean of 
the five quiet days per month available from the observa- 
tories of the Polar Year does not permit adequate des- 
cription of the monthly mean of Sq. Accordingly, means 
by months for the 12-year period 1922 to 1933 were de- 
rived, for stations between the northern and southern 
auroral zones. The means were taken so as to include 
homogeneous data intercomparable at all stations, using 
the same days and hours so far as possible. These means, 
corrected for noncyclic change, are illustrated in Figures 
54 to 69. 

It will be noted that the results agree well with those 
of Figures 50 to 53. The monthly m^ans are each based 



129 



130 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



on 60 days of the 12-year period, and delineate the aver- 
age amplitude and form of Sq at each station, and the 
transitional characteristics from month to month. In a 
previous volume, tables were given of mean monthly es- 
timates of Sq for each 10°-parallel of geographic lati- 
tude. These were derived by reading from smoothed 
graphs of the Fourier coefficients a n , bn up to n = 4, 
the values of a n , b n for each 10° -parallel of latitude. 
The results so found were next synthesized to give the 
results of Tables 1-L, 1-M, and 1-N in that volume. 
These tables, used in conjunction with later tables that 
provide factors which take into account the daily vari- 
ability of Sq, permitted the approximate correction of 
field-observations for the influence of Sq [1]. 

It should of course be remarked that Sq depends 
about as closely on geographic as on geomagnetic lati- 
tude, the differences being negligible in low latitudes and 
very slight in middle latitudes. In high latitudes, how- 
ever, Sq io itself presumably small, and the effects of 
disturbance may dominate even on international quiet 
days. In the work of the previous volume [1], it was 
convenient to use geomagnetic components for Sq, since 
these were also used for AV, P, and RV. The small 
differences in middle latitudes involved for the east com- 
ponent, resulting from the asymmetry of the Sq-field rel- 
ative to the geomagnetic axis, were not neglected, since 
the variation of Sq with longitude was taken approximate- 
ly into account at a later stage. 

Figures 70 to 85 give the values of Sq by ^"-paral- 
lels of latitude, as derived from interpolated and synthe- 
sized values. 

4. The dependence of Sq on longitude. --The varia- 
tions with longitude apparent from inspection of Figures 
40 to 49, presented in Chapter VI, and Figures 50 to 69 
in the present chapter would be expected on the basis of 
the dynamo-theory which is generally accepted as ex- 
plaining the main contribution of Sq. Apart from season- 
al influences, the air motions yielding the causative elec- 
tric currents in the atmosphere by dynamo-action seem 
likely to be most nearly symmetrical about the Earth's 
axis of rotation, but the lines of force of the vertical com- 
ponent of the Earth's main field, cut by the moving con- 
ducting air layers, are to the best first approximation 
symmetrical about the geomagnetic axis. Hence in low 
latitudes where the geographic and geomagnetic equators 
diverge most widely from one another, there must appear 
effects observable in Sq depending on the divergence of 
the two equators. The results for Huancayo, interpreted 
from this standpoint by McNish [26], seem cogent, and 
similar arguments can be brought to bear \n the case of 
Manila. The data of Figures 50 to 69 show the amplitude 
of the geomagnetic north component at Manila to be aug- 
mented above its expected value, though on a smaller 
scale than at Huancayo. 

In mapping the dependence of Sq on longitude in this 
equatorial belt of about 20° width in latitude, and cover- 
ing much of the Earth's surface, a great handicap is ex- 
perienced as a result of the paucity of data. It would 
seem highly desirable to locate an observatory near the 
junction of the geomagnetic and geographic equators, at 
an island near Baker Island in the Pacific, and at one or 
two additional equatorial sites in other longitudes. 

The world-wide features of Sq are well defined, al- 
though the oceans present extensive areas where no ob- 
servations of Sq have been made. As may be expected, 
there are small variations in the otherwise regular fea- 
tures of Sq which depend on highly localized conditions, 



such as those occasioned by the proximity of stations to 
induced electric currents flowing in the oceans. 

In order to obtain the approximate variation of Sq 
with longitude, the values of Figures 70 to 85 were sub- 
tracted from the observed values at all available ob- 
servatories. Results by hours were mapped on world 
charts, for each geomagnetic component. This was done 
in seeking the simplest possible distribution giving con- 
tours fully closed. In many regions the results so found 
are at best only a considered guess. Due to the highly 
tentative character of the results for many regions, ta- 
bles of the variation of Sq with longitude given in the 
preceding volume [1] included only values of field great- 
er than three gammas. Values for X' were given in 
Table l-O, a sample of which appears in the preceding 
volume. The values in Table 1-P for the Y' -component 
were considerably smaller in general than were those 
for the X' -component. In the case of the Z -component, 
the variation with longitude was particularly small, and 
it was not thought worth while to include a table for these 
small values (in general less than about five gammas). 

5. The variation in the amplitude of Sq with sunspot- 
cycle. - -Chapman [3] has studied the variation in form 
and amplitude of Sq with sunspot-cycle, for data on a 
world-wide scale for the years 1902 and 1905, and also 
for the station Greenwich for the long series of years 
1889 to 1914. The results indicated at most only a slight 
variation in form with sunspot-cycle. The amplitude of 
Sq was found to be about 30 per cent greater in sunspot 
maximum years than in minimum years. These findings 
were supported by extensive studies of Ellis [3] and 
Moos [16]. 

The results derived here for the years 1922 to 1933 
are also in good agreement. Examination revealed that 
the average phase and form of Sq differed little from 
year to year (except in special locations such as Huan- 
cayo), with the amplitude greatest near sunspot maximum. 

The dependence of amplitude of Sq on sunspot-cycle 
is conveniently examined by deriving the mean annual 
ranges in the H -component of Sq for international quiet 
days. Figure 86 shows the yearly averages of the daily 
amplitude of Sq for the period 1922 to 1933 for various 
stations. The results from station to station agree well, 
and changes in the averages from year to year corre- 
spond closely with the changes in yearly sunspot number. 
These data show that the regions of the Sun emitting the 
ultraviolet radiation which is responsible indirectly for 
Sq, attain their maximum effectiveness as radiators at 
the time of maximum sunspots. They show further that 
the change in amplitude of Sq from year to year is 
gradual. 

6. The daily variability of Sq .- -Figure 87 shows Sq 
on several selected international quiet days. Chapman 
and Stagg [28] examined the day to day changes in Sq 
for Eskdalemuir and Greenwich for quiet days of the 
period 1913 to 1923. They found the differences in field 
from average for these observatories closely correlated 
(correlation coefficient 0.77 in X and 0.84 in Y), and 
found less correlation for stations farther apart. They 
also found that the phase of S q is independent of the am- 
plitude. 

Hasegawa [3] considered in detail the changes in the 
Sq current systems on successive days showing marked 
differences in the amplitude of Sq. The changes in Sq 
revealed considerable shifts in the current system re- 
sponsible, both to the north and south of the average po- 
sition; this feature appeared also in a statistical study of 



THE SOLAR DAILY VARIATION ON QUIET DAYS, S q 



131 



the amplitudes of Sq carried out for the transitional sta- 
tion of Watheroo by Bartels [3]. 

In order to examine this question further, the day to 
day movement of the transition region in middle latitudes 
was estimated from changes in the H -component of force 
at the time of the noon maximum. Use was made of the 
shift in the monthly mean latitude distributions at noon 
for the stations Tucson, Lukiapang, and Watheroo. The 
average daily shift or oscillation about the average posi- 
tion of transition was several degrees of latitude. There- 
fore, in all regions except those in and near the zones of 
transition, where the value of Sq is in any case small in 
the component most affected ana varies only slowly with 
latitude in other components, there will in general be but 
a few abnormal days which will not be adequately de- 
scribed by averaged values. 

Although the phase of Sq is somewhat variable from 
day to day, and there are some daily variations in form, 
the value of Sq throughout low and middle latitudes can 
be estimated to a certain degree of accuracy on the basis 
of suitable multiplicative factors to be applied to the av- 
erage monthly mean in a component. The studies of 
Chapman and Stagg [3] indicate that the proportional in- 
creases or decreases in Sq relative to the normal or 
mean value are highly correlated from station to station. 
This finding was independently confirmed here by actual 
comparisons on individual days for many stations. It was 
therefore concluded that a suitable multiplicative factor, 
derived as a mean for several stations in low latitudes 



for which the usual Sq on each day is large in amplitude 
in H and only slightly affected by disturbance, would be 
useful. The procedure of relating the daily amplitude 
and phase of Sq to its average monthly value also af- 
forded the additional attractive feature of correcting for 
the variation in amplitude of Sq with sunspot-cycle. 

After some experimentation, it was found that a quan- 
tity derived by taking the mean hourly departure in H 
near noon from the daily mean in H, at an equatorial 
station, and dividing by the appropriate monthly average 
value obtained from 12 years of data, showed fairly good 
agreement from station for station. Such quantities de- 
rived from data of the period 1922 to 1933 therefore pro- 
vide valuable multiplicative factors applicable to the av- 
erages of Sq at stations in all latitudes. Comparisons 
revealed that on slightly disturbed days the discrepancies 
among stations were rather marked, but on such days the 
influence of disturbance in the higher latitudes is suffi- 
cient to mask results of the comparisons. 

The factors derived on the basis of individual low- 
latitude stations have been listed in Table 1-P, a sample 
of which appears in the preceding volume [1]. These af- 
ford useful estimates of Sq even on many days of storm, 
in view of the predominently large amplitude of Sq in H 
near noon near the equator as compared with the dis- 
turbance daily variation (Sp) there, which is ordinarily 
small in H. However, for Huancayo, it must be noted 
that the factors include a periodic effect as great as 20 
per cent due to the lunar daily variation. 



Table 103. List of magnetic observatories 



Station 


<t> 


X 


$ 


A 


¥ 


D 


Thule 


76.5 


291.0 


88.0 


0.0 


0.0 


-81.3 


Godhavn 


69.2 


306.5 


79.8 


32.5 


-17.5 


-57.9 


Score sby Sund 


70.5 


338.0 


75.8 


81.8 


-36.2 


-34.6 


Sveagruvan 


77.9 


16.8 


73.9 


130.7 


-46.2 


- 4.9 


Chesterfield Inlet 


63.3 


269.3 


73.5 


324.0 


14.9 


-12.6 


Calm Bay 


80.3 


52.8 


71.5 


153.3 


-32.2 


21.2 


Bear Island 


74.5 


19.2 


71.1 


124.5 


-37.9 


- 1.9 


Juliannehaab 


60.7 


314.0 


70.8 


35.6 


-13.8 


-43.4 


Fort Rae 


62.8 


243.9 


69.0 


290.9 


24.1 


37.5 


Point Barrow 


71.3 


203.3 


68.6 


241.2 


33.0 


28.7 


Tromso 


69.7 


18.9 


67.1 


116.7 


-30.8 


- 3.7 


Petsamo 


69.5 


31.2 


64.9 


125.8 


-27.6 


5.8 


Matotchkin Shar 


73.3 


56.4 


64,8 


146.5 


-22.4 


21.7 


College, Fairbanks 


64.9 


212.2 


64.5 


255.4 


27.0 


30.5 


Sodankyla 


67.4 


26.6 


63.8 


120.0 


-26.7 


3.0 


Dickson 


73.5 


80.4 


63.0 


161.5 


-12.8 


28.5 


Lerwick 


60.1 


358.8 


62.5 


88.6 


-23.6 


-13.6 


Meanook 


54.6 


246.7 


61.8 


301.0 


17.2 


26.4 


Sitka 


57.0 


224.7 


60.0 


275.4 


21.4 


30.2 


Eskdalemuir 


55.3 


356.8 


58.5 


82.9 


-20.4 


-14.3 


Lovo 


59.4 


17.8 


58.1 


105.8 


-22.1 


- 2.6 


Sloutsk 


59.7 


30.5 


56.0 


117.0 


-20.6 


4.4 


Rude Skov 


55.8 


12.4 


55.8 


98.5 


-20.6 


- 5.6 


Agincourt 


43.8 


280.7 


55.0 


347.0 


3.6 


- 7.6 


Abinger 


51.2 


359.6 


54.0 


83.3 


-18.4 


-11.9 


De Bilt 


52.1 


5.2 


53.8 


89.6 


-18.9 


- 8.9 


Manhay 


50.3 


5.7 


52.0 


88.8 


-18.2 


- 8.6 


Val Joyeux 


48.8 


2.0 


51.3 


84.5 


-17.5 


-10.5 


Swider 


52.1 


21.2 


50.6 


104.6 


-18.3 


- 1.6 


Cheltenham 


38.7 


283.2 


50.1 


350.5 


2.4 


- 7.1 


San Miguel 


37.8 


334.4 


45.6 


50.9 


-11.3 


-18.2 


San Fernando 


36.5 


353.8 


41.0 


71.3 


-13.6 


-12.2 


Tucson 


32.2 


249.2 


40.4 


312.2 


10.1 


13.9 


San Juan 


18.4 


293.9 


29.9 


3.2 


- 0.7 


- 5.2 


Teoloyucan 


19.8 


260.8 


29.6 


327.0 


6.6 


9.5 


Helwan 


29.9 


31.3 


27.2 


106.4 


-12.7 


0.0 


Honolulu 


21.3 


201.9 


21.1 


266.5 


12.3 


10.1 


Dehra Dun 


30.3 


78.0 


20.5 


149.9 


- 6.6 


1.1 


Lukiapang 


31.3 


121.0 


20.0 


189.1 


2.1 


- 3.6 


Au Tau 


22.4 


114.0 


11.0 


182.9 


0.6 


- 0.7 


Alibag 


18.6 


72.9 


9.5 


143.6 


- 7.2 


- 0.2 


Manila 


14.6 


121.2 


3.3 


189.8 


2.0 


0.5 


Huancayo 


-12.0 


284.7 


- 0.6 


353.8 


1.3 


7.4 


Vassouras 


-22.4 


316.4 


-11.9 


23.9 


- 5.0 


-13.0 


Elisabethville 


-11.7 


27.5 


-12.7 


94.0 


-11.7 


- 9.5 


Apia 


-13.8 


188.2 


-16.0 


260.2 


11.7 


10.7 


Batavia 


- 6.2 


106.8 


-17.6 


175.6 


- 0.9 


1.1 


Pilar 


-31.7 


296.1 


-20.2 


4.6 


- 1.1 


6.1 


Tananarivo 


-18.9 


47.5 


-23.7 


112.4 


-11.2 


- 8.3 


Mauritius 


-20.1 


57.6 


-26.6 


122.4 


-10.3 


-12.6 


Cape Town 


-33.9 


18.5 


-32.7 


79.9 


-13.7 


-24.7 


Watheroo 


-30.3 


115.9 


-41.8 


185.6 


1.3 


- 3.9 


Toolangi 


-37.5 


145.5 


-46.7 


220.8 


9.5 


8.5 


Amberley 


-43.5 


172.7 


-47.7 


252.5 


15.1 


18.0 


South Orkneys 


-60.8 


315.0 


-50.0 


18.0 


- 7.2 


+ 3.1 



132 



FIGURES 50-87 



Figure Page 

50(A)-53(C). Average daily variation, quiet days, geomagnetic components, winter, equinox, 

summer, mean of 12 months, and inhomogeneous data, Polar Year, 1932-33 134 

54-69. Solar daily variation on quiet days (S q ), various stations, geomagnetic components, 

January to December, winter, equinox, summer, and year, 1922-33 142 

70-85. Solar daily variation on quiet days (Sq), various geographic latitudes, geomagnetic 

components, January to December, winter, equinox, summer, and year, 1922-33 158 

86 (A) -(D). Yearly means of daily range of horizontal intensity (H), international quiet days, 

expressed as ratio to corresponding mean range at station for period 1932-33 167 

87(A)-(B). Solar daily variation (Sq) in geographic components X, Y, and Z, very quiet days, 

January 4, 5, and February 17, 1933 168 



133 



THULE 
(SS°0) 

GODHAVN 

(79°a) 

chesterfield INLET 
(73°S) 

JULIANNEHAAB 

(?o'a) 

FOOT RAE 
(69?0) 

POINT BARROW 
(6S°6) 

TROMSO 
(6 7°l) 

COLLEGE-FAIRBANKS 
(S4°S) 

SODA NX Y LA 
(63°8) 

LERWICK 
(62°S) 

MEANOOK 
(6I°8) 

SITKA 
(60°0) 

ESKDALEMUIR 
(5S°5) 

LOVO 

($e°i) 

SLOUTSK 
(56°0) 

RUDE SKOV 

(ss'a) 

AGINCOURT 

(ss'.o) 

ABINGCR 
(54°0) 



12 16 20 24 




4 S 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 




-*-*» 



X^ 



a 12 16 20 24 





az 



FIG 50(A)- AVERAGE DAILY VARIATION, QUIET DAYS, GEOMAGNETIC COMPONENTS, WINTER, POLAR YEAR, 
1932- JJ (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



134 



DE B1LT 

(S3?a) 

SWIDER 

(soTeJ 

CHELTENHAM 

(soli) 

TUCSON 

(10%) 



SAN JUAN 
(39%) 

TEOLOYUCAN 
(29° 6} NOV 1932, 
JAN, FEB 1933 



HELWAN 
(27°2) 



HONOLULU 
(21°) 



LUKIAPANG 
(20°0j 



AL/3AC 

(sTsj 



MANIL A 
(3°3) 



HUANCAYO 
(~0°6) 



ELISABETHVILLE 
(-12°?) 



PILAR 
(-20° 2) 



WATHEROO 
(-»°S) 



TOOLANOI 
(-46°?) 



AMBERL E Y 
(-47*7) 



SOUTH ORKNEYS 
(-S0°0) 






LOCAL GEOMAGNETIC HOURS 






X^ 




FIG. 50(B)- AVERAGE DAILY VARIATION, QUIET DAYS, GEOMAGNE T IC COMPONENTS, WINTER, POLAR YEAR, 
1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



135 



THULE 
(86°0) 

GODHAVN 
(79°8) 

CHESTERFIELD INLET 

(73°5)SEP 16,17 1932, 
MAR APR, SEP 3,5,6, 
1933 

JUL IANNEHAAB 

(7o°a) 

FORT RAE 
(69°0) 



POINT BARROW 
(68°6pCT 1931, 
MAR, APR 1933 

TROMSO 
(67?/) 



COLLEGE-FAIRBANKS 
<64°5)0CT, 1932 MAR, 
APR, SEP 1933 

SOD AN K YL A 
(63°8) 



LERWICK 
(62°5) 

MEANOOK 
(6I°8) 

SITKA 
(60°0) 

ESKDAL EMUIR 
(5B°S) 

LOVO 
(58°,) 

SLOUTSK 
(56°0) 

RUDE SKOV 
(55°8) 

ACINCOURT 
(55°°) 

ABINGER 
(54°0) 



4 8 12 16 20 24 






A *—^ 12 16 20 ' 24 1 6 4 8 12 ' 16 20 

LOCAL GEOMAGNETIC HOURS 









FIG. SltAl-AVERAGE DAILY VARIATION. QUIET DAYS, GEOMAGNETIC COMPONENTS, EQUINOX, POLAR YEAR, 
1932- JJ (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



136 



DE BILT 
(S3°8) 

SWIOCR 
(50°6) 

CHEL TENHAM 

(soft) 

TUCSON 
(*0U) 

SAN JUAN 
(29°9jSEP,OCT 
1932, MAR 1933 OS Z) 

TEOLOyUCAN ' 
(!9°6)SEP,0CT 
1932, APR 1933 

HEL WAN 
(27?2) 

HONOLULU 
(21°,) 

LUKIAPANG 
(20°0) 

AL/BAC 
(9°5) 

MANILA 
(3°3J 

HUANCAYO 
(-0°6) 



ELISABETHV1LLE 
(-I2°7)MAR,APR 
1933 

PILAR 
<-20?2) 

WAT HE POO 
(-41%) 



TOOLANCI 
<-46°7) 



AMBERLEY 

Hr??J 



4 8 12 16 20 24 





~0 ' 4 ' 8 '~I2 16 20 24 \ 6 ' 4 ' 8 1216 20 24 
LOCAL GEOMAGNETIC HOURS 








EIG- -51(B)- AVERAGE DAILY VARIATION, QUIET DAYS, GEOMAGNETIC COMPONENTS, EQUINOX, POLAR YEAR, 
1932-33 {GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



137 




na 5SfA)-AYERAGE DAILY VARIATION, QUIET DAYS, GEOMAGNETIC COMPONENTS, SUMMER, POLAR YEAR, 
I932-3J (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



138 



4 ^» 12 IS 20 2t\0 4 8 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 



OE BILT 
(53°6) 

SWIOER 

(so°e) 

CHEL TENHAM 

{soli) 

TUCSOU 
(40°4) 

SAN JUAN 
(29°9) 

TEOLOYUCAN 
(2»°6JMAY TO 
AUG I93J 

HE L WAN 
(27°2) 

HONOLULU 
(21°/) 

LUKIAPANG 
(20°0) 

AL IB AG 

(s°s) 

MANIL A 
(J°JJ 

HUANCAYO 
<-0°6) 

ELISABETHVILLE 
(-12°?) 

Pilar 
(-20°2) 

WATHEROO 
(-4I°B) 

TOOLANGI 
(-46?T) 

AMBERLEY 
(-4T°7) 

SOUTH ORKNEYS 

(-solo) 



4 8 12 16 20 24 




.jj...... ^ 









az 



FIG. 52(B)- AVERAGE DAILY VARIATION, QUIET DAYS, GEOMAGNETIC COMPONENTS, SUMMER, POLAR YEAR, 
1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



139 



4 .'*"&* ' 12 ' 16 ' 20 ' 24\6 4 a 12 16 20 ' 24 
*», LOCAL GEOMAGNETIC HOURS 
\ 



THULF 

ha°0)AUG 1932 
TO JUL 1933 



GOOHAVN 
(79°») 

CHESTERFIELD INLET 

(73°b)sEP IS, 1932 
TO SEP 9, 1933 

JUL IANNEHAA8 
(70°8) 

FORT RAE 
(69?0) 

POINT BARROW 
(68°6)OCT 1932 
TO AUG 1 1, 1933 

TROMSO 
(67?,) 

COLLEGE FAIRBANKS 

(64°SJ0CT 1932 
TO SEP 1933 

SODANKYLA 

(63°a) 

LERWICK 
(62°5) 

MEANOOK 

(6/°e) 



SITKA 
(60°0) 

ESKDALEMUIR 

(sals) 

LOVO 
(SB?,) 

SLOUTSK 
(56°°) 

RUDE SKOV 

(ss?e) 

AGINCOURT 

(ssfo) 

ABINGER 
(S4°0) 



»...-..£ 8 12 16 20 24 









FIG. 53(A)~AVERAGE DAILY VARIATION, QUIET DAYS, GEOMAGNETIC COMPONENTS, MEAN OF IZ MONTHS, 
POLAR YEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



140 



DE BILT 

(S3°a) 

SWIDER 
{50%) 

CHELTENHAM 
(SO?/) 

TUCSON 
(40°4) 

SAN JUAN 

(29°9)SEP, OCT 
1932, MAR 19 J J (£ Z) 

TEOLOYUCAN 

(29°6)SEPTONOV 
1932, JAN, FEB, APR 
TO JUL 1933 
HELWAN 

(27°2) 

HONOLULU 
(2,°,) 

L UK I A PANG 

(aoTo) 

AL /BAG 
(9°5) 

MAN/LA 
<3°3) 

HUANCAYO 

(-o°s) 

ELISABETHVILLE 
(-12*7) NOV 1932 
TO AUG 1933 

PILAR 
(-20°2) 

WATHEROO 

(-4/°e) 

TOOLANGI 
(-4S°7) 

AMBERLEY 
(-47°7) 

SOUTH ORKNEYS 
(-50%) 



4 8 12 16 20 24 





4 8 12 16 20 2410 4 a 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 





XT' 






FIG. 53(Bh- AVE RAGE DAILY VARIATION, QUIET DAYS, GEOMAGNETIC COMPONENTS, MEAN OF 12 MONTHS 
POLAR YEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



THULE 

(ea°o) 

AUG 1932 TO JUL 1933 

CHES TERFIEL INLET 

(73°5) 
SEP 1932 TO SEP 1933 

CALM BAY 
(7/Ts) 

JAN 1933 TO DEC 1933 

BEAR ISLAND 
(7/T/J 

OCT 1932 TO AUG 1933 

POINT BARROW 

(68°6) 
OCT 1932 TO AUG 1933 

MATOTCHKIN SHAR 

(64°e) 
JAN 1933 TO DEC 1933 

COLLEGE FAIRBANKS 

(64°S) 
OCT 1932 TO SEP 1933 

DICKSON 
(63°0) 
JAN 1933 TO DEC 1933 



4 a 12 16 20 24 





20 24 \0 4 a 12 16 20 24 

GEOMAGNETIC HOURS 




FIG- 53(C) -AVERAGE DAILY VARIATION, QUIET DAYS, GEOMAGNETIC COMPONENTS, INHOMOGENEOUS DATA, 

POLAR YEAR, 1932-33 



141 




FIG. S4-S0LAR DAILY VARIATION ON QUIET DAYS CSqJ. VARIOUS STATIONS. GEOMAGNETIC COMPONENTS. 
JANUARY, 1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



142 




riC.SS— SOLAR DAILY VARIATION ON QUIET DAYS (SqX VARIOUS STATIONS, GEOMAGNETIC COMPONENTS, 
FEBRUARY, 1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



143 




riG.56- SOLAR DAILY VARIATION ON QUIET DAYS CSq,X VARIOUS STATIONS, GEOMAGNETIC COMPONENTS, 
MARCH, 1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



144 




FIG.57S0LAR DAILY VARIATION ON QUIET DAYS (Sq), VARIOUS STATIONS, GEOMAGNETIC COMPONENTS. 
APRIL, 1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



145 




f i g. 58- solar daily variation on quiet days (s^x various stations, geomagnetic components, 
may', 1922-33 Geomagnetic latitudes indicated in parentheses') 



146 




riG.S9-S0LAR DAILY VARIATION ON QUIET DAYS (S<jjl VARIOUS STATIONS, 
JUNE, I9H-33 (GEOMAGNETIC LATITUDES INDICATED IN 



GEOMAGNETIC COMPONENTS, 
PARENTHESES) 



147 




FIG.6Q-S0LAR DAILY VARIATION ON QUIET DAYS (SqJ, VARIOUS STATIONS, GEOMAGNETIC COMPONENTS, 
JULY, 1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



148 




FIG.&t-SOLAR DAILr VARIATION ON QUIET DAYS (S^), VARIOUS STATIONS, GEOMAGNETIC COMPONENTS, AUGUST, 
1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



149 




EIG.62SOLAR DAILY VARIATION ON QUIET DAYS CSq), VARIOUS STATIONS. GEOMAGNETIC COMPONENTS. 
SEPTEMBER, 1922-33 {GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



150 




FIG.63-S0LAR DAILY VARIATION ON QUIET OArS (S^), VARIOUS STATIONS, GEOMAGNETIC COMPONENTS, OCTOBER, 
1922-33 {GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



151 




FIG.64-S0LAR DAILY VARIATION ON QUIET DAYS fSq), VARIOUS STATIONS, GEOMAGNETIC COMPONENTS, 
NOVEMBER. 1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



152 




EIG.6S-S0LAR DAILY VARIATION ON QUIET DAYS (Sy), VARIOUS STATIONS, GEOMAGNETIC COMPONENTS, DECEMBER, 
1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



153 




TI0.66-SOLAR DAILY VARIATION ON OUIET DAYS (Sq), VARIOUS STATIONS, 
WINTER, 1922-33 GEOMAGNETIC LATITUDES INDICATED IN 



GEOMAGNETIC COMPONENTS, 
PARENTHESES) 



154 




riG.er-soLAR daily variation on quiet days ts^), various stations, geomagnetic components, 

EQUINOX, 1931-33 {GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



155 




FIG.6BS0LAR DAILY VARIATION ON QUIET DAYS (Sq), VARIOUS STATIONS, GEOMAGNETIC COMPONENTS, 
SUMMER, 1922-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



156 




EIG.69-S0LAR DAILY VARIATION ON QUIET DAYS ( S<j >, VARIOUS STATIONS, GEOMAGNETIC COMPONENTS, 
YEAR, I92Z-3J (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



157 




FIG.TO— SOLAR DAILY VARIATION ON QUIET DAYS (Sq),IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, JANUARY, 1921-33 



i ' I! ' lb ' 20 ' H 



( + 10> 



(+40* 



<o> 



« -so J 



4 a I! IS 20 




4 a 12 16 20 24 

LOCAL MEAN HOURS 





riG.7l —SOLAR DAILY VARIATION ON QUIET DAYS (S<Z, IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, FEBRUARY, 1922-33 



158 




FK.72- SOLAR DAILY VARIATION ON QUIET DAYS (So), IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS. MARCH, 1922-33 



, LOCAL MEAN HOURS 




FIG 73-SOLAR DAILY VARIATION ON QUIET DAYS (SJ, IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS APRIL, 1922-33 



159 



(+eo') 



( +30') 



( + 40) 



(+30 ) 



( + 20) 



( + 10 J 



<0'i 



(-30) 



(-30) 



(-40 ) 



(-50) 



(-60) 



12 It 10 






HG. 74— SOLAR DAILY VARIATION ON QUIET DAYS ($j), IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, MAY, 1922-33 



( + 60) 



( + 40 ) 



( + 30) 



(+10) 



(0~) 



(-20 ) 



(-30) 



(-10) 



(-SO) 



(-60) 




16 20 24 
\ LOCAL MEAN HOURS 




d 8 12 16 20 24 




FIG.7S-S0LAR DAILY VARIATION ON QUIET DAYS {S^, IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, JUNE, 1922-33 



160 



(*60'j 

(+so'j 

i+40*J 

( + 30°) 
(+2o'j 

<+io'j 

C0°) 

(-10° J 



(-SO) 



(-60) 




12 16 20 2d 
^LOCAL MEAN HOURS 




4 B 12 16 20 24 




FIG76-S0LAR DAILY VARIATION ON QUIET DAYS (S^) > IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM - 

PONE NTS, JULY, 1912-33 




FIG. 77-SOLAR DAILY VARIATION ON QUIET DAYS (S^, IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, AUGUST, 1922-33 



161 




EIG.78-S0LAR DAILY VARIATION ON QUIET DAYS (Sq) f IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, SEPTEMBER, 1922-33 




FIG.79-S0LAR DAILY VARIATION ON QUIET DAYS (Sq), IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, OCTOBER, I9H-33 



162 



(+S0°) 



( + «J 



(+/0J 



(-10 ) 



(-20 ) 



(-40 ) 



(-SO ) 



(-60 ) 



12 16 20 




4 6 12 16 20 24 

LOCAL ME AH HOC/OS 




12 16 20 24 



.■ r iri 




riG.aQ-SOLAR DAILY VARIATION ON QUILT DAYS (S tt ! l IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, NOVEMBER, 1922-33 



I +S0') 



< +20% 



O 4 8 12 16 20 




8 12 16 20 24 
LOCAL MEAN HOURS 




4 a 12 16 20 24 




FIG.8I-SOLAR DAILY VARIATION ON QUIET DAYS (Sq), IN VARIOUS GEOGRAPHIC LATITUDES, GEOM. NETIC COM- 

PONENTS, DECEMBER, 1922-33 



163 



t + 60") 



t + 50' J 



( + 40") 



1*10 ) 



(-50 ) 



(-60) 



12 16 10 




S 12 16 10 24 

LOCAL MEAN HOURS 




4 6 12 16 20 24 




FIG.82- SOLAR DAILY VARIATION ON QUIET DAYS (Sq^lN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, WINTER, 1922-33 




FIG.83-S0LAR DAILY VARIATION ON OUIET DAYS (Sq), IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 
PONENTS, EQUINOX, 1922-33 



164 



l* SO') 
(+*<f) 

( + 30°) 
( + 20°) 
(+10°) 
<0°) 
(- 10°) 
(-20°) 
1-30°) 
(-10°) 
(-50°) 
(-60°) 





12 It 20 24 




FIG.84--S0LAR DAILY VARIATION ON QUIET DAYS (Sql/ZV VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 

PONENTS, SUMMER, 1922-33 




FIG.aS-SOLAR DAILY VARIATION ON QUIET DAYS (i^), IN VARIOUS GEOGRAPHIC LATITUDES, GEOMAGNETIC COM- 

PONENTS, YEAR 1922-33 



165 



OllVti JO 37V0S 





167 



THULE 

(B8°o, 76°s) 

GODHAVN 
(79°B,69°2) 

JULIANNEHAA8 
(70°8, 10? 7) 

FOOT RAE 

(69°o,62°a) 

troms6 
(67°i,ea?7) 

SODANKYLA 

(e3?e,67.°t) 

L ERWICK 
(62°S.60°I> 

MEANOOK 
<6I?B, S4°6) 

SITKA 
<60?0, 57°0J 

E SKOAL EMUIR 
C58°S,55?3) 

LOVO 
(S8°l,59°4> 

SLOUTSK 
(S6?0, 59°. 7) 

RUDE SKOV 
(55°8,SS°8) 

AGINCOURT 
(5S°0,43°B) 

ABINGER 
(54?0,5I°2) 



DE BIL T 
(S3°8,S2°l> 



VAL JOYEUX 
(SI°3,48°B) 






AX 
_i i l i i i— 



t — i — i — i — i — i — i — i — i — i — i — i — rri — i — i — i — i — i — i — i — i — i — i — i — r 
4 8 12 16 20 24 \0 4 8 12 16 20 24 

LOCAL MEAN HOURS 



^w 




ay 




a/ 



FIG:87(A)-SOLAR DAILY VARIATION (Sq), IN GEOGRAPHIC COMPONENTS, X, Y, AND Z, VERY QUIET DAYS i.C-0.0) JAN- 
UARY 4,5, AND FEBRUARY 17, 1933 (GEOMAGNETIC AND GEOGRAPHIC LATITUDES INDICATED RESPECTIVELY IN PARENTHESES) 
LEGEND' •~+*~' MEAN OF JANUARY 4.5, AND FEBRUARY 17, 1933) ' « « ' MEAN OF JANUARY 5 AND FEBRUARY 17, 1933 



168 



smoER 

(S0T6,S2'l) 

CHELTENHAM 
(50'. 1,38'. 7) 

TUCSON 
(40° 4, 32' 2) 

SAN JUAN 
(29°9, IB°4) 

HELWAN 
(iTfg, 29° 9) 

HONOLULU 
(2I°1 ,2I°3) 

LUKIAPANC 
(,20°0,3I°3) 

ALIBAC 
(9°S,I8?6> 

MANIL A 
(3°3, I4°6) 



HUANCAYO 
\.-0°6,-l2°0) 

ELISABETHVILLE 
(-12*7, -ll'.7) 

PILAR 
(-20*2, -3I°7 

H/ATHEROO 
(4l'.B,- 3d? 3 ) 

TOOL ANSI 
(-4S°.7,-37°S> 

AMBERLEY 
(-47?7,-43°S) 



SOUTH ORKNEYS 
(-50*0, -eO'B) 



^^ 




T — I — I — I — I — I — i — I — I — I — I — r 
4 B 12 It 20 24 

LOCAL MEAN HOURS 



■^7- 





4 8 12 16 20 24 





^\. 



HZ 



FIG.87(B)-S0LAR DAILY VARIATION (St)), IN GEOGRAPHIC COMPONENTS, X, Y, AND Z, VERY QUIET DAYS (C-0.0) JANUARY 
4,5, AND FEBRUARY 17, 1933 (GEOMAGNETIC AND GEOGRAPHIC LATITUDES INDICATED RESPECTIVELY IN PARENTHESES) 



169 



CHAPTER VIII 
THE DISTURBANCE DAILY VARIATION, S D , AND STORM-TIME VARIATION, D st 



1. Introduction. - -The geomagnetic disturbance fields 
of our environment introduce effects of some practical 
importance in human affairs. When at times they be- 
come intense, they are associated with serious disrup- 
tions in world-wide radio communications. The rapid 
changes in field also induce currents in telegraph cables, 
and interfere with transformer -operation in power -trans- 
mission circuits, thus disrupting services of commercial 
organizations. The disturbance fields can, in certain 
highly restricted regions, slightly affect navigation by 
compass, and near the auroral zones, they can temporar- 
ily limit the accuracy of navigation by other components 
of the main field. They likewise are accompanied by 
brilliant auroral displays in the higher latitudes. 

At any station recording geomagnetic changes, those 
due to disturbance appear highly variegated and complex. 
It was thought interesting and instructive to consider to 
what extent one might, from knowledge of the disturbance 
field at one station, estimate the manifestations of dis- 
turbance elsewhere. A simple case in which such in- 
formation would be of practical value is that of improv- 
ing homogeneity of measurements of the main magnetic 
field at survey stations. However, as mentioned in the 
preceding volume [1], we were unsuccessful in achiev- 
ing a practical scheme, applicable anywhere, for obtain- 
ing such improvement. 

Since the average aspects of disburbance seem 
rather orderly and simple, as compared with transient 
aspects over short intervals of time, an extensive sum- 
mary is given here of average characteristics of disturb- 
ance. These may be found useful in various practical ap- 
plications, and also provide a useful store of information 
for scientific study. In describing how the average char- 
acteristics of disturbance were derived, the discussion 
here will be confined mainly to those aspects of analysis 
dealing with our approach to removing the effect of dis- 
turbance from survey measurements of the main field. 

In the problem of adjusting magnetic observations for 
disturbance effects, in so far as the reduction from mean 
of hour to mean of day is concerned, the disturbance daily 
variation Sp (that part of disturbance which varies main- 
ly with local time), and storm -time variation D s t (the 
part of disturbance which depends on time of onset of 
disturbance) are of great importance in high latitudes. In 
low and middle latitudes, where by far the largest num- 
ber of field-observations have been made, the values of 
Sq and D s t are in general relatively small in compari- 
son with Sq, even on the average international disturbed 
day. However, on a few highly disturbed days in each 
year, Sp and D s t assume a dominant role in all lati- 
tudes. Although the large fluctuations appearing in the 
geomagnetic field on such days are of considerable sci- 
entific interest, for the present problem they are usually 
of slight practical import, since observers at field-sta- 
tions have from experience found measurements on such 
days unreliable, and have postponed them until more qui- 
et conditions have been restored. Usually, therefore, re- 
ductions from mean of hour to mean of day are made for 
data obtained under the more quiet conditions, and large 



corrections for Srj and D s t, for regions between the 
northern and southern auroral zones, are rarely involved. 

For the polar regions, where Sj) is in general large 
even on international quiet days, a correction would be 
useful, if it could be made. Because the number of field- 
observations there are comparatively few, uncorrected 
observations are likely to leave estimates of secular 
change completely undetermined. 

Unfortunately, the corrections in high latitudes, al- 
though large, are for several special reasons not readily 
derivable. The Srj-field is there highly complicated in 
pattern and this pattern, furthermore, oscillates irregu- 
larly to the north and south about the position of the av- 
erage auroral zone. The field also undergoes highly er- 
ratic changes during short intervals of time. Hence, the 
number of observatories necessary to determine Sj) with 
fairlv high precision at intervening points would need to 
be so large as to become, in all probability, impractical. 

The problem immediately in hand is that of determin- 
ing whether or not something can be done at present with 
the small number of field-observations already made in 
high latitudes. Since the number is small, the possibility 
that each field-observation should be treated individually 
must be considered. Such treatment might meet with 
some success in certain years, such as the Polar Year, 
1932-33, when there were about 30 magnetic observato- 
ries in operation in north polar regions. However, in 
other years there were few or no polar observatories. 
Hence, the only alternative is that of attempting to pre- 
dict, from values of Sj} and D s t in lower latitudes, the 
corresponding probable values at a field-station in high 
latitudes. This is a problem of great difficulty, and its 
solution in convenient and satisfactory form has not been 
found. 

The disturbance daily variation has been studied by a 
number of writers. One of the more important of early 
studies was that of Moos [16] who seems first to have 
separated the observed average storm -field into parts 
varying according to local time and storm -time, Sq and 
D s t, respectively. This was effected by averaging a num- 
ber of storms at Bombay. Chapman [3] in a series of 
papers has considered data for 40 storms of moderate 
intensity at many stations, using a procedure similar to 
that of Moos. In this work he derived the approximate 
latitude distributions of Sp and D s t,for Srj from the 
pole to the equator, and for D s t in all except for the 
polar regions. He also derived possible atmospheric- 
electric current systems to account for both Sj) and D s t. 
In a somewhat earlier and highly important work, Birke- 
land [29] made extensive studies of magnetic storms and 
bays on individual days, indicating by numerous examples 
the world-wide distribution of the storm-field. Other 
studies, notably by Broun [30], van Bemmelen [31], Ad. 
Schmidt [32], Ludeling [33], together with the more re- 
cent studies of Stagg [34], Slaucitajs and McNish [35], 
Forbush [36], and Vestine [10], have served further to 
clarify the geographical distribution and description of 
the field of storms. Vestine and Chapman [37] made pre- 
liminary derivations of Srj and D s t from the extensive 



171 



172 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



data afforded by the Polar Year observations, 1932-33, 
with particular reference to determinations of Sd and 
D s t (as shown by daily means) in high latitudes. A later 
study indicated the dependence of Sd on longitude and 
extended the results for high latitudes southward to the 
equator [38]. 

2. Disturbance daily variation Sp on disturbed days, 
by seasons and year, Polar Year. 1932-33. --Following 
procedures similar to those previously adopted for de- 
termining Sq, the disturbance daily variation on dis- 
turbed days was derived for stations of the Polar Year, 
1932-33. Care was taken to maintain strict homogeneity 
in the choice of data for all stations. Due to the fact that 
records were missing on a few international disturbed 
days at some stations, days next in order of intensity of 
disturbance were substituted at all stations. Such days, 
used in obtaining the averages according to season and 
year, were as follows: May 2, 1933, was substituted for 
the international day May 29, 1933, and July 8, 10, 11,17 
18, 1933, for the international days July 9, 23, 24, 27, 
1933. Includea also in the data are the results for sta- 
tions falling into a nonhomogeneous category for intervals 
of time indicated in the figures discussed in succeeding 
paragraphs. 

A and B of Figures 88 to 91 show the seasonal and 
annual means of the geomagnetic components of Srj, for 
the Polar Year taken from September 1, 1932, to August 
31, 1933. The observations are given in terms of local 
geomagnetic time, reckoned relative to the geomagnetic 
north pole as reference. 

It will be noted that the components of So vary main- 
ly with geomagnetic latitude. The north component re- 
verses in sign near geomagnetic north latitude <? =72°, 
attains its maximum range at the auroral zone, again re- 
verses in sign near <5 = +55°, and is small and nearly 
uniform in magnitude throughout low and middle latitudes. 
In general, its magnitude is largest in the early morning 
and early evening. The geomagnetic east component is 
largest within the interior of the auroral zone, reverses 
in sign at the auroral zone, and then remains small and 
fairly uniform in low and middle latitudes. The vertical 
component shows a large and pronounced morning maxi- 
mum just inside, and a small minimum just outside the 
auroral zone, both of which appear also in the evening 
but reversed in sign. This component reverses in sign 
near the equator and is relatively small in low and mid- 
dle latitudes. 

The changes with season are most marked in high 
latitudes where Sd is smallest in winter and largest in 
summer. 

The seasonal averages of Sd based on the single 
year of observation reveal certain irregularities. These 
are no doubt due to the fact that only 20 days were avail- 
able per season. Moreover, since the quiet-day data of 
Figures 50 to 53, shown in Chapter VII, include also 
some part of Sd, this small part of Sd actually has been 
removed from the disturbed day values. 

We have previously noted from Figures 50 to 53 that 
Sp is appreciable even in the average of international 
quiet days in high latitudes. Hence Sd is present prac- 
tically every day of the year, and the data for all days 
minus quiet days usefully supplement those for interna- 
tional disturbed days. Figures C and D of 88 to 91 
give the results for all days minus quiet days of the Po- 
lar Year, 1932-33, thus providing data respecting Sd 
from about 120 days per season. Figures 91(E) and 91(F) 
give annual means from the inhomogeneous data, for 



disturbed days minus quiet days and all days minus quiet 
days, respectively, in high latitudes. It will be noted that 
the results in general fully confirm those obtained from 
the data consisting mainly of international disturbed days, 
except for a reduction in amplitude resulting from a ne- 
cessarily different choice of days. 

3. Disturbance daily variation Sn by months, seasons, 
and year, 1922 to 1933 . --Figures 92 to 107 give the values 
of Sp derived mainly from international disturbed days 
minus quiet days averaged by month, season, and year for 
the period 1922 to 1933, arranged by stations. Unfortu- 
nately there are no data for high latitudes, but the aver- 
age characteristics of Sd between the northern and south- 
ern auroral zones are fairly well defined. The transitions 
in character of field are more definitely delineated than 
in Figures 88 to 90, with which good agreement is shown. 

4. Disturbance daily variation Sn by month, season, 
and year, for various parallels of latitude. --Figures 108 
to 123 give the values of Sd from geomagnetic latitude 
62°.5*N to 62°. 5 S as found from Fourier syntheses of 
the data. The data of the Polar Year, 1932-33, have been 
reduced to the means of 1922 to 1933 to obtain approxi- 
mate correction for the difference in the average intensi- 
ty of disturbance. 

5. Variation of S p with longitude . --The data of Fig- 
ures 108 and 123 give the values of Sd averaged around 
parallels of geomagnetic latitude, approximately adjusted 
to a circular auroral zone in latitude $ = +67°. These 
data could in turn be subtracted from the observed values 
at each station for one or more positions of the Sun rela- 
tive to the geomagnetic meridian A = 180° to obtain the 
additional part of Sd dependent on geomagnetic longitude. 
This was done in the case of the geomagnetic north com- 
ponent for the Sun in a position in the plane of A = 0. No 
important change in amplitude with longitude was found. 

6. The storm-time variation D s f.--The storm -time 
variation D s t forms a characteristic feature of magnetic 
storms, and its course depends on the time reckonedfrom 
the commencement of disturbance. In the case of Chap- 
man's derivation of D s t, the force components for 40 
storms in low and middle latitudes, arranged according 
to storm -time, were meaned, the values of Sd tending 

to cancel by virtue of their dependence on local time. 

In the present study, in order to obtain possible in- 
dications of the character of the storm-time variation in 
high latitudes, a similar derivation was made for 11 
storms of the Polar Year, 1932-33. Since the number of 
storms available was small and there was considerable 
variation in their intensities, the data for each storm 
were multiplied by a weighting factor which was the same 
for all latitudes, and was given by the value of the maxi- 
mum range in D s t near the equator. The equatorial val- 
ue of D s t was obtained by meaning, according to Green- 
wich time, the values in H at Alibag, Honolulu, and San 
Juan, stations spaced roughly 120° apart in longitude so 
that the values of Sd might cancel because of their de- 
pendence on local time (Figure 124A). B and C of Fig- 
ure 124 show the results found for D s ^ in the geomag- 
netic north, east, and vertical components of the polar - 
year storms. Although there is evidence of the presence 
of a 24-hour periodic component, suggesting incomplete 
removal of Sd, the general latitude distribution of D s t 
is clearly shown for each of several groups of stations, 
the stations being arranged in order in each group ac- 
cording to decreasing geomagnetic latitude. 

In B .of Figure 124, which illustrates the results 
found for high latitude stations, it is clear that the D s t 



THE DISTURBANCE DAILY VARIATION, S D , AND STORM-TIME VARIATION, D st 



173 



in X' begins with a zero or negative initial value (except 
possibly for the mean of Thule and Godhavn, where the 
detailed course of D s t appears to be masked somewhat 
by Sjj) which decreases to a minimum in 20 to 24 hours, 
followed by a fairly gradual recovery to a value near the 
initial value in about 70 hours. In the case of the most 
southerly group, consisting of Sodankyla, Meanook and 
Sitka, the initial value appears slightly positive. In Y' 
the value of D s ^ appears to be comparatively small, and 
must actually be nearly zero, since it is likely that some 
of the systematic regularities shown are due to incom- 
plete removal of Sj). The Z -component of D s t appears 
small near the pole. Proceeding southwards, it becomes 
large and positive, its magnitude being similar that of 
the X' -component but opposite in sign. The large in- 
crease in amplitude in the Z -component shown for the 
two groups of stations near <$ = 70°, as compared with 
values for the adjacent groups to the north and south, is 
particularly interesting. On the basis of Chapman's cur- 
rent system [3] it suggests that the two opposed halves 
of the polar current system of storms vary in size with 
the course of storm -time, the part accompanied by west- 
ward currents along the auroral zone being the larger 
when D s t is larger [37]. At the auroral zone, as shown 
by the results for Tromso and College, the characteris- 
tic changes in the Z -component of D s t already resemble 
those in lower latitudes, which are in general negative in 
sign. At Sodankyla, Meanook, and Sitka, the transition in 
Z is complete. 

C of Figure 124 shows, on a scale two times as open 
as that of B, the geomagnetic components of Dst found 
for the region between the northern and southern auroral 
zones. The results given here, corrected from D s t at 
the equator to the level of intensity of the storm of May 1 , 
1933, are in good agreement with those found by Chapman 
[3] for the mean of 40 moderate magnetic storms fortius 
region. In X' the value of D s t attains a maximum near 
the equator, about which field-changes appear to be ap- 
proximately symmetrical. In Y' the time -changes are 
small in all latitudes. In Z the values are small and in 
general positive throughout low and middle latitudes of 
the Northern Hemisphere and are of similar magnitude 
but opposite in sign in the Southern Hemisphere. 

7. The values of S D and D gt_ on individual days of 
storm. --In two important memoirs, Birkeland [29] ex- 
amined in detail the vector changes of disturbance. He 
plotted vector field-changes for various instants of time 
on maps of the world in the case of many disturbances 
and bays. These maps, while providing important data 
for the study of individual magnetic storms, do not give 
separately the component parts Sd and Dst- Later Ves- 
tine and Chapman [37] made a derivation of the current 
systems for single hours of the storms of October 15, 
1932, and May 1, 1933, which permitted a separation of 
the current system into the component parts Sd and Dst. 

Figure 125 shows estimated values of Sd and D s t 
for the storm of May 1, 1933, obtained after removal of 
Sq by first meaning every alternate hour in H according 
to Greenwich mean time for the stations Alibag, Honolu- 
lu, and San Juan to get the value of D s t, and then, after 
subtraction of D s t, taking means according to local time 
in order to obtain Sd- 

After the average value of D s t was obtained for the 
three stations, it was reduced to its equatorial value; 
then, on the assumption that the latitude distribution in 
this case was the same as that for the X' -component of 
D m i, values of D s t were computed for various stations. 



The value of D s t obtained in this manner for each station 
was then subtracted from the observed value, the latter 
first being corrected for Sq, to give a computed value of 
S D . It appears from Figure 125(C) that Sd varies in am- 
plitude with D s t, but the time -phase remains near its av- 
erage value. 

It was thought possible that a law could be found from 
which Sd could be calculated when D s t is known. It was 
noted first that the computed values of Sd were not di- 
rectly proportional to D s t- A search was next made, but 
without success, for a function of storm -time which would 
be effective at all stations; the relationship appeared to be 
a complicated function of position of the station, and its 
general nature remained undetermined. This result sug- 
gested that Sd and Dst should each show considerable 
variability in values for individual days from the average 
value of many days, in general form and phase. However, 
the removal of values of Sq before determining Sd and 
D s t might be subject to some error, thus adding further 
complication to the apparent storm-field. A to I of Fig- 
ure 126 show for many stations the hourly mean depar- 
tures from the mean of day in the geomagnetic north, 
east, and vertical components for the storm of April 30, 
1933. These reveal the general world-wide characteris- 
tics of disturbance, but they show no evidence of a simple 
relationship between Sd and D s t- It should, however, be 
borne in mind that the irregular features of disturbance, 
Dj (discussed in a later section) are not fully removed 
in taking hourly means of magnetic data. It would seem 
necessary to remove in some way Di (as well as Sq) 
from these data. An important consideration which sug- 
gests the necessity for this procedure is that bays, al- 
though evincing mainly an So-field with little D s t in evi- 
dence, except near the auroral zone, nevertheless fre- 
quently appear during storms. Their appearance dis- 
turbs and masks any relationship sought between Sd and 
D s t which might possibly have a systematic pattern. 

Figure 127 illustrates actual hourly mean departures 
from mean of day (without removal of Sq), at many sta- 
tions. These are shown for several days, on Greenwich 
mean time, with international character -figures, C, of 
different values, as follows: October 9 (C = 0.9), De- 
cember 17 (C = 1.3), 1932; February 23 (C = 1.5), April 
18 (C = 1.1), June 5 (C = 0.0), and August 31 (C = 0.1), 
1933. The reader will find it interesting to compare the 
departures for February 23, where storm conditions pre- 
vail, with those of the very quiet day of June 5. These 
figures are helpful in a descriptive sense, although the 
original purpose for which they were derived was that of 
training computers and draftsmen for later work. 

One point emerging from the present study is that 
there seems little hope of predicting accurately the 
changes in the polar disturbance -field from the field- 
changes observed in low latitudes in the reduction of 
magnetic observations. It appears, however, that useful 
corrections in low and middle latitudes might be effected, 
and further study might well result in a practical method 
of making such corrections. 

8. The irregular geomagnetic disturbance D ^ . - -The 
irregular features of disturbance seem first to Have been 
extensively studied by Birkeland [29]. From maps show- 
ing the world-wide field -distributions in terms of vectors, 
he concluded that there were world-wide diminutions in 
horizontal intensity, of some minutes' duration, among 
the oscillatory changes appearing on magnetograms, and 
also others for which the sign and magnitude depended 
on the local time of occurrence at a station. He also 



174 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



made extensive studies of bays which may also be re- 
garded as a manifestation of Di [3]. 

Studies of the data on bays for the Polar Year, 1932- 
33, have shown that the pattern of the field of bays very 
closely resembles that for Sd- However, there is also 
present in the field Gf bays a part which, when averaged 
along parallels of geomagnetic latitude, is not zero, and 
shows an especially large negative value just inside the 
auroral zone. The latter is clearly due to the component 
D s t of bays. Thus there is a qualitative but not a detailed 
correspondence between tne field of bays and Sd as de- 
rived here. 

The pattern of field evinced during bays appears, 
without great change in general form, on any day of the 
year, although there are systematic changes with season. 
Thus, from a station located near the center of the au- 
roral zone, where the field-changes are large and nearly 
independent, in magnitude, of the local time of appear- 
ance of a bay, one can hope roughly to estimate the mag- 



nitude and time -variation of the bay at any point else- 
where on the Earth's surface. 

The average geographical distribution of bays has 
been roughly estimated by Silsbee and Vestine [39]. 
These results should, however, be further amplified by 
taking into account the considerable seasonal changes in 
high latitudes, thus permitting the preparation of tables 
likely to give useful estimates of the intensity and time- 
variation of bays in all latitudes. The estimates may not 
be entirely successful, however, near the auroral zone, 
due to the expansions and contractions of this zone during 
a bay. 

9. The latitude distributions of noncyclic change, NC- - 
Figure 128 shows the latitude distributions of the non- 
cyclic change for international quiet days, all days minus 
quiet days, and disturbed minus quiet days of the Polar 
Year, 1932-33, in the geomagnetic north, east, and verti- 
cal components. 



FIGURES 88-128 



Figure Page 

88(A)-910). Average daily variation, disturbed minus quiet days (Sd) and all minus quiet 
days, geomagnetic components, winter, equinox, summer, mean of 12 months, inhomo- 
geneous data, and indicated for horizontal plane by vector diagrams, Polar Year, 1932-33 . 176 

92-107. Disturbance daily variation (Srj), disturbed days, January to December, winter, 

equinox, summer, and year, 1922-33 198 

108-123. Disturbance daily variation on disturbed days (Sp) in various geomagnetic latitudes, 
geomagnetic components, January to December, winter, equinox, summer, and year, 
1922-33 214 

124(A). Storm-time variation (D s t) in equatorial regions as given by San Juan, Alibag, and 
Honolulu as departures from annual mean, by sunspot rotations, September 1, 1932, to 
August 31, 1933 230 

124(B)-(C). Average storm-time (D s t) weighted average of 11 storms, 1932-33 232 

125(A). Hourly mean departures of geomagnetic north component from mean of April 30, 1933 . 234 

125(B). Storm-time variation (D s t) from San Juan, Alibag, and Honolulu, average times factor . . 235 

125(C). Disturbance daily variation (Sq) plus solar daily variation (Sq) from (A) minus (B) . . . 236 

126 (A) -(I). Hourly mean departures in geomagnetic north, east, and vertical components from 

mean of April 30, 1933, storm of May 1, 1933 237 

127(A)-(I). Hourly departures from mean of day, geomagnetic north, east, and vertical com- 
ponents 246 

128. Variation with geomagnetic latitude in noncyclic change for quiet days, all days minus 
quiet days, and disturbed days minus quiet days, geomagnetic north, east, and vertical 
components, by year and by seasons, 1932-33 255 



175 



THULE 

(es'o) 

GODHAVN 
(7*8) 

CHESTERFIELD INLE1 

(n't) 

JUL IANNEHAAB 

(roTaJ 

FORT RAE 
(1*0) 

POINT BARROW 

(ears) 

TROMSO 
{*'■') 

COLLEGE FAIRBANKS 
(*>*) 

SODANKYLA 

(sj'a) 

LERWICK 

(tils) 

MEANOOK 

(eiTe) 

SITKA 

(so°o) 

ESKOAL EMUIR 
(SB'S) 

LOVO 
(58'l) 

SLOUTSK 

(saTo) 

RUDE SKOY 
(»■*) 

AOINCOURT 

(ss'o) 

ABINGER 

(»'o) 



4 a ii is io 24 




IS 16 20 14\0 4 a 
LOCAL GEOMAGNETIC HOURS 





H 




6Y 





V 




FIGaB(A)~AYERMiE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, fed, GEOMAGNETIC COMPONENTS, 
POLAR YEAR, I932-3J (GEOMAGNETIC LATITUDES INDICATED IN FHRENTHESESJ 

* NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



176 



oe BILT 
(M'S) 

SWIDER 
(S0'6) 

CHELTENHAM 
(SO',) 

TUCSON 
(40%) 

SAN JUAN 
(29°9) 

TEOLOYUCAN 

(29°6)nOV 1932, 
JAN.rEB 1933 

HELWAN 
HONOLULU 

(uTi) 

LUKIAPANG 

(2o'o) 

ALIBAG 
(9'S) 

MANIL A 
(3'3) 

HUANCAYO 
(-0-6) 

ELISABETHVILLE 

PILAR 
(-20'l) 

WATHEROO 
(-"'«) 

TOOL ANGI 
(-46'7) 

AMBERLEY 
SOUTH ORKNEYS 

{-sore) 



4 8 12 16 20 24\0 4 8 12 16 20 

LOCAL GEOMAGNETIC HOURS 





ax' 




..—■S '•• N> 




4 8 12 16 20 24 






az 



r/cat (B)-AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DArS, (Sot. GEOMAGNETIC COMPONENTS, WINTER, 
POLAR YEAR, 1932-33 GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



177 



THUL£ 

(aero) 



GOOHAVN 



CHESTERFIELD INLET 



JUL IANNEHAAB 
(70°B) 



FORT RAE 
(69°0) 



POINT BARROW 
(63?6j 



TROMSO 
(t?'l) 



COLLEGE FAIRBANKS 
(64%) 

SOOANKYLA 

(t3?a) 

LERWICK 
(62°5) 

MEANOOK 
(61%) 

SITKA 
(tO°0> 

ESKDALEMUIR 
(SB'S) 



LOI/0 

(saTi) 



SLOUTSK 
(56%) 



RUDE SKOV 

(ss°a) 

AGINCOURT 

into) 



ABINGER 
(U'O) 



4 a 12 It 20 24 





4 a 12 It 20 24 

LOCAL GEOMAGNETIC HOURS 






6> ' 



4 a 12 It 20 24 




FIG. 88(C)- AVERAGE OAILV VARIATION ALL MINUS QUIET DAYS, GEOMAGNETIC COMPONENTS, WINTER, POLAR 
VEAR, I9J2-J3 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 

NOTE PARTICULARLY THAT SCALES TOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



178 



DC BILT 
(S3t») 

SWIDER 
CHELTENHAM 

(soTi) 



TUCSON 
(40%) 



SAN JUAN 

(29^»)SCP. OCT 
1931, MAR 1933 (£Z) 

TEOLOYUCAN 

(2l'e) NOV 1932, 
JAN. fee 1933 

HEL WAN 
(27?2) 

HONOLULU 
(2,'l) 

LUX/APANG 

(!oro) 

ALIBAG 

(»-s) 

MANIL A 
(3'3) 

HUANCAYO 

(-ore) 



ELISABETHVILLE 

(-ah) 



PILAR 
WAT HE POO 
TOOLANOI 

<-<e'r) 



AMBERLEY 

(-4T?7) 



SOUTH ORKNEYS 

(-$o'o) 



6 4 8 13 /e 20 24 



4 a 12 It 20 24 

LOCAL GEOMAGNETIC HOURS 






12 16 20 24 



EIG. 880)— AVERAGE DAILY VARIATION, ALL MINUS QUIET DAYS, GEOMAGNETIC COMPONENTS, WINTER, POLAR 
YEAR t 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



179 



THULE 

(as'o) 

GOOHAVN 

(ra'e) 

CHESTERFIELD INLET 

(73°5)SEP IS-30, 
OCT 1932, MAP, APP, 
SEP 9,19 J J 
JULIANNEHAAB 

(ro°a) 

EOPT PAE 
(S9°0) 

POINT BAPPOW 

(6B°.6)OCT 1932. 

MAP, APP 1933 

TROMSO 
<6 7°l) 



COLLEGE FAIRBANKS 

(64°5)OCT 1932. 
MAP, APP, SEP 193 J 

SODANKYLA 
(63°S) 



L EPWICK 
(62°S) 

MEANOOK 
(6,lB) 

SITKA 
(60°0) 

ESKDALEMUIP 

(sbTs) 

LOVO 
(sa'l) 

SLOUTSK 
(S6°0) 

PUOE SKOv 

(ss?a) 

AGINCOURT 

(ssro) 

ABINGER 
($4'0) 





7^ 



*v^ 



LOCAL GEOMAGNETIC ROUPS 




12 16 20 24 








FIG. 39(A)- AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, (Sn), GEOMAGNETIC COMPONENTS, EQUI- 
NOX, POLAR KEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 

* NOTE PARTICULARLY THAT SCALES FOP GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



180 



OE bil r 
(S3?a) 

SwIDER 
(50?6) 

CHELTENHAM 
{50ll) 

TUCSON 
(40°4) 

SAN JUAN 

(29°9)SEP,OCT 
1932, MAR 1933 02) 

TEOLOYUCAN 

(29°.6)SEP, OC T 
1932, APR 1933 

HEL WAN 
(27°2) 



HONOLULU 
{2,°l) 

LUX I A PA NO 
(20%) 

AL IB AG 
(9°S) 

MANILA 
(3°3) 

HUANCA VO 

i-o'e) 

ELISABETHVILLE 

(-I2°7) MAR, APR 
1933 

PILAR 
WATHEROO 

(-4i°e) 

TOOL ANSI 
(-46'7) 

AMBERLEy 
(-47*) 

SOUTH ORKNEYS 

(-sob) 



8 12 16 20 24 





\ .--•■ 







S 12 IS 20 24 





rSO 



nG.89(Bl-AVERAGE 
NOX. 



DAILY VARIATION, DISTURBED MINUS QUIET DAYS, (So), GEOMAGNETIC COMPONENTS, EQUI- 
POLAR YEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



181 



CHESTERFIELD INLET 
SEP 15-30. 
MAR. APR. 
SEP 1-9.1933 
JUL IANNEHAAB 

(70?eJ 



THULE 

(aa°o) 



GODHAVN 

(79°a) 



(?3°5) Si 
C 193!, A 



PORT RAE 
(69°0) 

POINT BARROW 

(68°6)OCT 1931, 
MAR. APR 1933 

TROMSO 
(67?,) 



COLLEGE FAIRBANKS 

(64?5)0CT 1932. 
MAR, APR, SEP 1933 

SOOANKYLA 
(63°S) 



LERWICK 

(62'S) 

MEANOOK 

(si°a) 

SITKA 
(60?0) 

ESKOALEMUIR 

(seTs) 

LOVO 

(sa'ij 

SLOUTSK 
(S6?0) 

RUDE SKOV 

(ssfaj 

AGINCOURT 

(ss'oj 

ABINGER 
(S4°0) 






-***- 





■ a -°- - Jt 





-=^V- 




Fia 39(C)- AVERAGE DAILY VARIATION, ALL MINUS QUIET DAYS, GEOMAGNETIC COMPONENTS, EQUINOX, POLAR 
YEAR, 1932-33 (.GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



182 



0£ BILT 
(S3?s) 



SWIDER 

(sole) 



CHEL TENHAM 
(50°,) 

TUCSON 
(40° 4) 

SAN JUAN 
(29°9)SEP, OCT 
1932, MAR 1933 (2 Z) 

TEOLOYUCAN 
(29°6) SEP, OC T 
1932. APR 1933 



HEL WAN 
(27'2) 

HONOLULU 
1*1-1) 

LUKIAPANG 
(20°0) 

AL IB AG 
(9?S) 



MANIL A 
(3?3) 

HUANCAYO 

(-o°s) 

ELlSABETHVILLE 
(-I2°.?)maR,APR 
1933 

PILAR 
(-20°2) 



WATHEROO 

(-4i'a) 



TOOLANGI 
(-46°?) 



AMBERLEY 



SOUTH ORKNEYS 

(solo) 



O 4 a 12 16 20 24 





^y^ - s 



-r^- 




AX' 






AY' 



12 16 20 





FIG 89<0>— AVERAGE DAILY VARIATION, ALL MINUS QUIET DAYS, GEOMAGNETIC COMPONENTS, EQUINOX, POLAR 
YEAR, 1932-33 GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



183 




rtG.90(*)-AYERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, (Sol GEOMAGNETIC COMPONENTS, SUMMER, 
POLAR YEAR, 1931-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 

« 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



184 



OE BILT 

(sj°a) 

SWIOER 

(sore) 

CHEL TENHAM 
(SOJ) 

TUCSON 
(40°4) 

SAN JUAN 
(29.9) 



TEOLOYUCAN 

(29°6)MAY TO 
AUG 1933 

HEL WAN 
(Z7h) 

HONOLULU 
(2,?,) 



LUKIAPANG 
(20°0) 

AL IB AG 

(A) 

MANILA 
(3°3) 

HUANCAYO 

(-o'e) 



ELISABETHVILLE 
(-12°.?) 



PILAR 
(-10°.*) 

WATHEROO 
(-4I°b) 

TOOL ANGI 

(-4e°.T) 

AMBERLEY 

SOUTH ORKNEYS 
(-i0°0) 



4 8 12 16 20 24 



4 S 12 16 20 24 

LOCAL GEOMAGNETIC HOURS, 




.a-^o-o-o-o- ^. 





J -r*' -"-a..." "^„ 




a 12 16 20 24 





FlG.90(B)-AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, <Sq), GEOMAGNETIC COMPONENTS, SUMMER, 
POLAR YEAR, 1932-33 GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



185 



FOP T RAE 
(69%) 



POINT BARROW 

(66°6)mAY. JUN, 
JUL. AUG l-U, 19*3 



THULE 

faa'oj AUG 1931 
MAY TO JUL 1933 

GODHAVN 
(79?8j 



CHESTERFIELD INLET 
(73°i) 



JULIANNEHAAB 

(70?a) 



TROMSO 
(67?,) 



COLLEGE FAIRBANKS 
(6**5) 



SODANKYLA 
(63°8) 

LERWICK 
(62°S) 

MEANOOK 

(eifaj 

SITKA 
(60°0) 

ESKDALEMUIR 

(se's) 

LOYO 
(58°,) 

SLOUTSK 
(56°0) 

RUDE SKOV 

(ss'a) 

AGINCOURT 
(55°0) 



ABINGER 
(54'0) 



12 16 20 24 





9 ' 12 ' 16 ' 20 ' 24 1 6 * 8 

T\ LOCAL GEOMAGNETIC HOURS 



12 16 20 24 








FIG. 900-AVERAGE DAILY VARIATION, ALL MINUS QUIET DAY'S, GEOMAGNETIC COMPONENTS, SUMMER POLAR 
YEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



186 



OE BIL T 
(Sj't) 



SWIOER 
(SO'6) 

CHEL TENHAM 

(so',) 

TUCSOU 
(40°4) 

SAN JUAN 
(29°9) 



TEOLOVUCAN 
(29°i)MAY, JUN, 
JUL. AUG 1933 

HELWAN 



HONOLULU 

(*fy 



LUKIAPANG 
(20°0) 

AL IB AC 
(9°S) 



MANILA 
(3°3) 

HUANCAYO 
(-0°6) 

ELISABETH\/ILLE 
(-I2°7) 



PILAR 
(-20°2) 



WATHEROO 



TOOLANGI 
(-46?T) 

AMBERLEY 
(-47??) 



SOUTH ORKNEYS 

(-soroj 



B 12 16 10 24 










4 a 12 IS 20 24 




r/aSOO- AVERAGE DAILY VARIATION, ALL MINUS QUIET DAYS, GEOMAGNETIC COMPONENTS, SUMMER, POLAR 
YEAR, IB32-3J (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



187 




riG.91 (A)— AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, (%)), GEOMAGNETIC COMPONENTS, MEAN OF 
12 MONTHS, POLAR YEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



188 



DC BILT 
($3°B) 

SWIDER 

(so°e) 

CHEL TENHAM 

(SO?/) 

TUCSON 

(40U) 

SAN JUAN 

(29°9)SEP,0CT 
1932, MAR 1933 (aZ) 

TEOLOYUCAN 

(29°6)SEP TO NOV 
193a, JAN. FEB. APR TO 
AUG 1933 
HE L WAN 
(27°!) 

HONOLULU 
(2,°,) 

LUK/APANG 
(20°0J 

ALIBAG 
(9°5) 

MANILA 
(3°3) 

HUANCAYO 
(-0°6) 



ELISABETHVILLE 
(- I2°7JN0V 1932 
TO JUL 1933 

PILAR 
(-20°2) 

WATHEROO 
(-4I°B) 

TOOLANGI 
(-46° 7) 

AMBERL E r 
(-*'■>) 

SOUTH ORKNEYS 

, (-so°o) 



12 16 20 24\0 4 B 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 








12 16 20 24 





FIG 91(B)— AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, fcl, GEOMAGNETIC COMPONENTS, MEAN OF 
12 MONTHS, POLAR YEAR y I9J2-JJ (.GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



189 



THULE 

(Sa°0)AUG 1932, 
TO JUL 1933 

GODHAVN 

(79°a) 



CHESTERFIELD INLET 
(?3°S) SEP IS, 1932 
SEP 9,1933 

JUL IANNEHAAB 
(70°B) 



FORT RAE 
(69°Oj 



POINT BARROW 
(66°6)OCT 1932 TO 
AUG II, 1933 



TROMSO 
(67?,) 



COLLEGE FAIRBANKS 

(6A°SjOCT 1932 TO 

SEP 1933 



SOOANK YL A 
(63°6) 



LERWICK 
(62?S) 

MEANOOK 

(e,?aj 

SITKA 
(60°0) 



ESKOALEMUIR 

(sah) 



LOVO 

(se°,) 



sloutsk 
(se'oj 



RUOC SKOV 

(ss'e) 



AGINCOURT 

(sifoj 

ASlNGER 
<S4'0) 




=N- 



i jin'i' * ■ 1 1 1 1 ■ •*" i ■ i ■ . 



* ' ■ ■ * * * ■ 



LOCAL GEOMAGNETIC HOURS 







AZ 



Z^* 



rid.0 HC)— AVERAGE DAILY VARIATION, ALL MINUS QUIET DAYS, GEOMAGNETIC COMPONENTS, MEAN OF It 
MONTHS., POLAR YEAR, 1932-33 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



190 



oe BUT 

(sx'a) 

SWIOER 

(soU). 

CHEL TENHAM 

(so'O 

TUCSON 
(40°4) 



■3 A* l<4 i/UHd 

(29°9)S£P,0CT 
1332. MAR 1933 (£ Z) 

TEOLOYUCAN 
(29°6JSEP TO NOV 
1932, JAN, EEB. APR 
TO AUG 1933 
HELWAN 
(27°2) 



HONOLULU 
(2I?I) 

LUKIAPANG 
(20°0) 

ALIBAG 
(9'S) 



MANIL A 
(3*3) 



HUANCAVO 

(-ore) 



ELISABETHvlLLE 

(-I2°T) NOV 1932 
TO JUL /933 

PILAR 

(-to'z) 



WATHEROO 
(-4,'S) 



TOOL ANGI 



AMBERLEY 
(-47?7) 

SOUTH ORKNEYS 
(-SO'O) 



12 IS 20 24 






4 8 12 IS 20 24 

LOCAL GEOMAGNETIC HOURS 




'- »-<^— "i*wj ■ u^^ zs 



~*" ~* 




12 16 20 24 




riC. 91(D)- AVERAGE DAILY VARIATION ALL MINUS QUIET DAYS, GEOMAGNETIC COMPONENTS, MEAN Of 12 
MONTHS, POLAR YEAR, 1932- JJ (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



191 



THULE 

(aa'o) 

AUG 1932 TO JUL 1933 

CHESTERFIELD INLET 

(T3li) 
SEP 1932 TO SEP 1933 

CALM BAY 

JAN I93J TO OEC 1933 

BEAR ISLAND 

(7l'l) 
OCT 1932 TO AUG 1933 

POINT BARROW 

(68°6) 
OCT 193! TO AUG 1933 

MATOTCHKIN SHAR 

(64'B) 
JAN 1933 TO DEC 1933 

COLLEGE FAIRBANKS 

(64°SJ 
OCT 1932 TO SEP 1933 

DICKSON 

(63° 0) 
JAN 1933 TO DEC 1933 




4 8 12 16 20 24 \0 4 S 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 





FIG. 91 (E) -AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, (Sq) GEOMAGNETIC COMPONENTS, 
INHOMOGENEOUS DATA, POLAR YEAR, 1932-33 



192 



THULE 

(aa'o) 

AUG 1932 TO JUL 1933 

CHESTERFIELD INLET 

(T3?5j 
SEP 1932 TO SEP 1933 

CALM BAY 

(T'fi) 
JAN 1933 TO DEC 1933 

BEAR ISLAND 

(Tl'lJ 
OCT 1932 TO AUG 1933 

POINT BARROW 

(63?6) 
OCT 1932 TO AUG 1933 

MATOTCHKIN SHAR 

(64°3) 
JAN 1933 TO DEC 1933 

COLLEGE FAIRBANKS 

(64°S) 
OCT 1932 TO SEP 1933 



DICKSON 

(63?0) 
JAN 1933 TO DEC 1933 



4 8 12 16 20 24 





20 24 \0 4 a 

LOCAL GEOMAGNETIC HOURS 






FIG 9/ (FJ —AVERAGE DAILY VARIATION, ALL MINUS QUIET DAYS, GEOMAGNETIC COMPONENTS, INHOMO- 

GENEOUS DATA, POLAR YEAR, 1932- 33 



193 




FIG. 91(0)- AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, (Sq), INDICATED FOR HORIZONTAL PLANE, 
BY VECTOR- DIAGRAMS LOCAL GEOMAGNETIC TIME, AND FOR VERTICAL INTENSITY, (a) YEAR AND (i) WINTER. POLAR 

YEAR, I93P - 33 



194 



GEOMAGNETIC NORTH 

-ias 




LOCAL MEAN HOURS 




r 



?■«/* 






VERTICAL INTENSITY 



L±J 



lX. 



GEOMAGNETIC NORTH 

'103 




FIG. 91 (H)- AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, (Sp) , INDICATEO FOR HORIZONTAL PLANE, 
BY VECTOR -DIAGRAMS LOCAL GEOMAGNETIC TIME, AND FOR VERTICAL INTENSITY, (a) YEAR AND (b) WINTER, POLAR 

YEAR, 1932-33 
(NOTE-- MATOTCHKIN SHAR, DICKSON AND CALM BAY ARE FOR THE YEAR 1)33, BEAR ISLAND IS FOR OCTOBER 1332 THROUGH AUGUST, 1933) 



195 



i 12 IS 

LOCAL MEAN HOURS 



I I | I I I I ' | I I I I I | I i I I I 
6 I! IB 

LOCAL MEAN HOURS 



GEOMAGNETIC NORTH 





JULIANNEHAAB 
$■70.8 







VERTICAL INTENSITY 



(a) 



LjJj 



■ ■ I ' ■ 



GEOMAGNETIC NORTH 



GODHAVN 
f'T9.B 



vA i?jA 



CHESTERFIELD INLET 
f'TJ.S 

IZS 




JULIANNEHAAB 

f-ro.a 







VERTICAL INTENSITY 



I I I I I I 



FIG. SI (I) -AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, (Sq) INDICATED FOR HORIZONTAL PLANE, 
BY VECTOR- DIAGRAMS LOCAL GEOMAGNETIC TIME, AND FOR VERTICAL INTENSITY, (a) EQUINOX AND (t) SUMMER, 

POLAR YEAR, 1932 -JJ 



196 



I I I I I I I I I I I I I I I I I I 

6 12 IS 

LOCAL MEAN HOURS 



GEOMAGNETIC NORTH 






MEANOOK 
f-6 1, a 



I I I I | I I I I I | I I I I I | I I I I 
6 I! IB 

L OCAL MEAN HOURS 




-SO 

'VERTICAL intensity 

( a >-,!0 

— I ' 



COLLEGE 

FAIRBANKS 

'12.9 







MEANOOK 

f-ei.e 





VERTICAL INTENSITY 



(o) 



FIG. 31 (J)— AVERAGE DAILY VARIATION, DISTURBED MINUS QUIET DAYS, <S D ~i, INDICATED FOR HORIZONTAL PLANE, 
BY VECTOR -DIAGRAMS LOCAL GEOMAGNETIC TIME, AND FOR VERTICAL INTENSITY, (a.) EQUINOX AND (b) SUMMER, 

POLAR YEAR, 1932-33 



197 



SOOANKLYA 
(6J°S, I20°0) 



LERWICK 
t 62'S, e#6) 



SITKA 
(60°0, 2TS°4) 



ESKOALEMUIR 

(sa's, a?9) 



rude skov 

(SS°8. 93' 'St 



AGINCOURT 
{SS°0, J47°0I 



ABINGER 

(S4°o, a J! j> 



D£ BILT 
ISJ'B, B9°S) 



YAL JOYEUX 

(Si? j, aSsi 



CHEL TEN HAM 
{SO? I, JSOTS) 



TUCSON 
(40°4, 3I2°2) 



HONOLULU 



ALIBAG 
(9% 143°$) 



MANILA 

(3fj, lasfie) 



HUAHCAYO 

(-o?6, JSJ'a> 



WATHEROO 

i-4i"e, i as" 6) 



AMBERLEY 
(-47?7, 2S2°S) 





1 4 a I! 16 20 24 

LOCAL GEOMAGNETIC HOURS 




^r 





i i i i i i i i i i i i_i 



■200 



FIG.S!-DISTURBANCE DAILY VARIATION (S D ), DISTURBED DAYS. JANUARY, 1921-33 {GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



198 



SODANKYLA 
(63?S. I20?0i 



l erwick 

(82? 5, 88^61 



SITKA 
(80° 0. 275?4j 



ESKDAL EMUIR 
<58.°5. 82?9J 



RUDE SKOV 
(55°8.98?5J 



AGINCOURT 
(55°0. 34T?0J 



ABINGER 
(54°0.83?3j 



BE Bit T 
(S3? 8, 89? 6) 



YAL JOYEUX 
{51° 3. 84? 5 J 



CHEL TEIJHAM 
(50? I. 350? S J 



TUCSON 
(40°4,3I2?2J 



HONOLULU 
(2I?I.266°S) 



ALIBAC 
(9?S. 143° 6) 



MANILA 
( 3?3, 1 89° 8) 



HUANCAYO 
i-0°e,353?8) 



VYA THEROO 
i-4l?8, I8S?6> 



AMBERLEY 
(-47°T,2S2°5) 



4 8 12 16 20 24 




^7^ 




ax' 



-i — l — i — i — i — i — i — l — l — l — l — l — r 

4 8 12 18 20 24 

LOCAL GEOMAGNETIC HOURS 







-i I I I L 



FIG.93- DISTURBANCE DAILY VARIATION (S D >, DISTURBED DAYS, FEBRUARY. 192?- 33 (GEOMAGNETIC LATITUDES 
AND LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

' NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



199 



SODANKLYA 

{fj'e, i20'o) 



LERWICK 

(62°s, aa°s> 



SITKA 
i60°0, 2TS°4) 



ESKOA L EMUIR 
(5d°5, 32°9) 



RUDE SKOV 
(SS'e, 98°1) 



AGINCOURT 
(SS°0, 347°0) 



ABINGER 
(54°0, aj°j) 



0£ BIL T 
(53?B, 8916) 



VAL JOYEUX 
tS'?J, 84°S) 



CHEL TEN HAM 
(S(f/, 350° S) 



TUCSON 
i.40'4, 3I2°2) 



HONOLULU 
t.2l°l, 2S6°5) 



ALIBAG 
(9°5, I43°6) 



MANILA 
13°3, ISO'S J 



HUANCAYO 
(-0*6, JSJ'B) 



WA THEROO 
(-4I°B, I0S%) 



AMBERLEY 
(-4?^ 2S2°S) 




•^ 



*"^ 



~sr 



4 S 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 




*«^ 




. i ■ I I l_l_ 





EIG. 94- DISTURBANCE DAILY VARIATION (S D ). DISTURBED DAYS. MARCH. l9!f-33 (GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



200 




FIG.9S- DISTURBANCE DAILY VARIATION (Sq), DISTURBED DAY S, APRIL , 1911-33 (.GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



201 



SODANKLYA 
(6TB, I20'0) 



Sitka 
(eo'o, 3?s'4) 



ESKOALEMUIR 
{SB'S, 82'9) 



RUDE SKOV 
(SS'S, 93'S) 



AGINCOURT 
(SS'O, 34T"0) 



ABINGER 
(S4°0, B3"3) 



OE BILT 
(SJ'B, 39'6> 



YAL JOYEUX 
iSl'j, BJ'S) 



CHEL TENHAM 
(SO'/, JSO'S) 



TUCSON 
(40°4, 3I2'2) 



HONOLULU 
(2l'l, 266'S) 



ALIBAO 
( 9 S, 143. 6/ 



MANIL A 
(3'3, IBS'SI 



HUANCAYO 
i-O'S, 3S3'8) 



WATHEROO 
(-dl'S, IBS"6) 



AM BE RLE Y 
(-4Ti7,gSlTS) 




^7* 



y^ 



t — i — i — r 



LOCAL GEOMAGNETIC HOURS 






•2 H 20 24 





F/G. 96 -DISTURBANCE DAILY- VARIATION {Sq), DISTURBED DAYS, MAY, I9H-33 (GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

* NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



202 



SODANKYLA 
<83°9. I20T0) 



L ERWICK 



SITKA 
( 60°0, 2 75?4> 



ESKDALEMUIR 
( S3°S, 82°9) 



RUDE SKOV 



AGINCOURT 

(ss°o, 3jr°o> 



ABINGER 
IS4°0,83°3) 



DE BIL T 
( S3°3, 89?6J 



I AL JOYEUX 
15I°3,84°5J 



CHEL TENHAM 
( .50.°/, 3S0°5J 



TUCSOU 
(40°4, 312°!) 



HONOL UL U 
(21? '/, 266°SJ 



ALIBAC 
(9°S. I43°6) 



MAN/L A 
<3-3°l89°8) 



HUANCAYO 
i-0°6.3S3°6> 



WATHEROO 
l-4l?8, ISS°6> 



AMBERLEY 
i-47°7. 252°SJ 



4 8 12 16 20 24 






T — I 1— I — I 1—1 1 1 1 I r 

4 8 12 IC 20 24 

LOCAL GEOMAGNETIC HOURS 






FIG. 97 - DISTURBANCE DAILY VARIATION (Sq), OIST URBED DAYS, JUNE, 1922-33 (GEOMAGNETIC LATITUDES 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

' NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



203 



SODANKYLA 
i.l3'». I20°0) 



LERWICK 

i6!?s.ea'6i 



SITKA 
i60°0, 27S°4) 



ESKOALEMUIR 
{S8°S.82°9J 



DUDE SKOV 
(5S?8,98°S) 



AGINCOURT 
(S5°0.34?°0J 



ABINGER 
(54?0.83°3) 



DE BIL T 
(S3°8,89°6> 



UAL JOVEUY 
(5I°3,84?5> 



CHEL TENHAM 
(S0?I,3S0°5J 



TUCSON 
(40°4,3I2° 2) 



HONOLULU 
(21° I. 266° S) 



ALIBAG 

(9° 5 , 143° 6) 



MANILA 
(3"3, IB9°8) 



HUANCAYO 
i'0°.6.3S3°.B> 

IVATHEROO 
(-4l?e, IBS°6) 

AMBERLEY 

(-47?r. is!°s> 




LOCAL GEOMAGNETIC HOURS 







J 1 I I I I L- 



r/C.Se- DISTURBANCE DAILY VARIATION <Sq). DISTURBED DAYS, JULY, 19!?- S3 (GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARC DIFFERENT THAN FOR OTHERS 



204 



SOOANKLYA 
(63'8, IZO'O) 



LERWICK 

(Sirs, etf.6) 



SI TKA 
(60'0, ITS. 4) 



ESKDALEMUIR 

(sa'.s, a2'9> 



RUDE SKOV 
(Sys, 98'S) 



AGINCOURT 
(SS'O, 34 7"0) 



ABINCER 
(S4'0, 8X3) 



OE BUT 
(S3' a, SST6) 



VAL JOYEUX 
(Sl'3, 8S.5) 



TUCSON 
(40' 4, 3 12" 2/ 



HONOLULU 
(2ft, 266' S) 



ALIBAO 
(9'S, I43"6) 



MANILA 

(3'3. lae'a) 



HUAHCAYO 
<-0*«. 3SJ!8) 



WATHEROO 

(-4/ra, ies*6i 



AUBERLEY 
(-477?, 2S2?Sj 




V*V^ 



^\ 



ax' 



LOCAL GEOMAGNETIC HOURS 






FIG. 99- DISTURBANCE DAILY VARIATION (Sq), DISTURBED DAYS, AUGUST, 1921-33 (GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY- IN PARENTHESES) 

' IWTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



205 



SOOANKYLA 
(SJft, IKXO) 



LERWICK 



SITKA 



ESKDALEMUIR 

(sets, a?a 



rude skov 

(SS°B, 98°5) 



AOINCOURT 
(SS°0,347?0) 



ABINGER 
(S4°0. B3?3) 



DE BILT 
(53°a.89?6) 



VAL JOYEUX 
(Sl°3, B4°5) 



CHEL TENHAM 
(50.°/. 3S0?S) 



TUCSOU 
(40°4, 31!° 2) 



HONOL UL U 
{!l°l. ?66?S) 



AL IB AG 
(9°S. I43?C) 



MANIL A 
(J°J, IB9?S) 



HUANCAYO 
(-0°C, 3S3°B) 



WATHER00 

(-4i°e. ies.°t) 



AMBERLEY 
(-47?7, 2S2?S) 




1 — i — i — I — I — I — I — I — I — I — r- 
14 4 » I! 16 X 

LOCAL GEOMAGNETIC HOURS 



*^ 



J± 



-7^~ 






-i — i — i — i — r 



8 I! IS 10 14 




FIG. 1 00 -DISTURBANCE DAILy VARIATION (Sq), DISTURBED DAYS, SEPTEMBER, I922-Z3 (GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY 1 IN PARENTHESES) 

* MOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



206 



SOOANKLYA 
(6j'a. I20°0, 



LEBWICK 
<62'S, BS"6l 



BuDE SKOV 
(55'8,9S'S) 



OE BIL T 
(53's;S9V/ 



CHCL tenham 
KSO'i, ISO'S) 



HONOLULU 
2I'I, 266'Sl 



ALIBAG 
i9'5, I43'6) 



MANILA 

iJ'j./es's) 



AMBEBLEY 
L-47'7, 252'SJ 



4 8 H 16 . 20 






LOCAL GEOMAGNETIC HOUBS 




_^~^ ., 



4 6 12 16 20 34 





FIG.IOI-DISTURBANCE DAILY VARIATION (S D ), DISTURBED DAYS, OCTOBER, 1923-33 (GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

' NOTE PABTICULABLY THAT SCALES FOB GRAPHS IN AUBOBAL REGIONS ARE OIFFEBEMT THAN FOB OTHEBS 



207 



SODANKYLA 

(ej°e. no?0) 



LERWICK 



SITKA 
(60.°0. 27S°4) 



FSKDALEMUIR 
(58°S.82°9) 



RUDE SKOV 
(55°8.98°S> 



AGINCOURT 
(55?0.347°0) 



ABINGFR 
(54?0. 83°3) 



OE B/L T 
(53°8,89°6) 



VAL JOYEUX 
(5I°3, 84°5) 



CHEL TENHAM 
(S0°l.35O?S) 



TUCSON 
(40°4.3I2°2) 



HONOL UL U 
(2I°I, 266°}) 



ALIBAG 
(9°S, I43°6) 



MANILA 
1 3°3, I89°8> 



HUANCAYO 
t -0°6. 353°B> 



WA THEROO 
(-4I°8.I8S°6> 



AMBERLEY 
(-47° 7. 252° 5) 



8 12 16 20 24 




1 — i — I — i — I — r- 



-i — i — i — i — i — r 
12 16 20 24 
LOCAL GEOMAGNETIC HOURS 





t — i — i — i — r~ 



12 16 20 24 





FIG.IOZ- DISTURBANCE DAILY VARIATION (S K DISTURBED DAYS. NOVEMBER, 1921-33 (GEOMAGNETIC LATITUDES 
AND LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 
NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



208 



SODANKYLA 
(63°S. I20°0) 



LERWICK 

i62°s,ae°6) 



SITKA 
(60?0,27S°4J 



£ SKOAL EMUIR 
(Se°5, 82°9) 



RUDE SKOV 
( SS°B, 98° 5/ 



AGINCOURT 
(5S°0, 347°0) 



ABINGER 
(S4°0,83°3J 



DE BILT 
iS3°B.89°6j 



VAL JOYEUX 
< 5l°3. 84°5) 



CHELTENHAM 
< 50° I. 350?Sj 



TUCSOU 
{40°4.3I2°2J 



HONOL UL U 
( 31° I, 266° 5/ 



ALIBAG 
(9?S, 43° 6) 



MANILA 
(3°3, I89°8l 



HUANCAYO 
<-0°6.353°8) 



HATHEROO 

(-4I°8. ias°6) 



AMBERLEY 
<-4 7°7,2S2°S) 



LOCAL GEOMAGNETIC HOURS 







FIG. 103 -DISTURBANCE DAILY VARIATION ( Sq), DISTURBED DAYS, DECEMBER. I9PP-J3 I GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



209 



SODANKYLA 
(6J?8, I20°0) 



LERWICK 

( 62°s,ae°6j 



SITKA 
( 60?0,2 7 5°4) 



ESKDALEMUIR 

{.sa°s,82°9j 



RUDE SKOV 
(5S?8,98?SJ 



AGINCOURT 
(55° 0. 347. 0) 



ABINGER 
(54°0,83?3) 



DE BIL T 
(53?B,89°6J 



val joyeux 

(5 l°.3,84°5) 



CHELTENHAM 
lS0°l,3S0°Sl 



TUCSON 
(40°4,3I2°2) 



HONOLULU 
(2I?I,266°SJ 



ALIBAG 
{9.5°l43°6l 



MA NIL A 
13°3, I89°8) 



HUANCAYO 
i.-0°6,3S3° 8) 



WATHEROO 
i-4l?8,/3S°6 I 



AMBERLEY 
l-47?7,252°Sl 



12 16 20 24 




4 8 12 It 20 24 

LOCAL GEOMAGNETIC HOURS 





J I I I I I I I I I 1 I L 





riG.IOA-OISTURBANCE DAILY VARIATION (S D ), DIST URBED DAYS. WINTER, 1922- 33 (GEOMAGNETIC LATITUDES 
AND LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 



NOTE PARTICULARLY THAT SCALES TOR GRAPHS IN AURORAL REGIONS ARE DITfERENT THAN FOR OTHERS 



210 



SODANKYLA 
(63°. 8. I20°0) 



L ERWICK 
{62°.S, BB°6 ) 



SITKA 
(60?0, 27S?4) 



ESKOALEMUIR 
{SB'S , 82?9) 



RUDE SKOY 
<SS°a,96?SJ 



AGINCOURT 
(SS°0, 347?0) 



ABINGER 
(S4°.0,B3?3) 



DE BILT 

( S3°8, 89?6 ) 



VAL JOYEUX 
(SI?3,B4?SJ 



CHELTENHAM 
(S0°. 1 ,350° 5) 



TUCSON 
(40?4,3I2°2J 



HONOLULU 
(21° I , 266° 5 ) 



ALIBAC 
(9°S. I43°6) 



MAN/LA 
(3°3, IB9°B) 



HUANCAYO 
<-0°6,3S3°8 ) 



WATHEROO 
t -■"?«, IBS' 6) 



AM8ERLEY 
(-A7?7, 252°S) 



t — i — i — i — r 





_t — i — i — 1_ 



4 B 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 





T — 1 1 1 1 — I — I — r 



-I — I — r 
20 24 





EIGJOS-DISTURBANCE DAILY VARIATION (S D ), DISTURBED DAYS. EQUINOX, 1922-33 (GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



211 



I — i — i — i — r — i — r — i — i — i — i — i — r 
) 4 8 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 



SODANKYLA 
l6fS.I20°0> 



LEPWICK 
( 62"S , 83°6 ) 



SI TKA 
itO'0,275'4 1 



ESKOALCMUIR 
( S6°S, 32°9) 



ACINCOUPT 
(S5'0 ,347°0> 



ABINGEP 
( 54°0,83°3) 



DE BIL T 
I Sj'a . 89°6 I 



VAL JOYEUX 
(Sl'3 ,S4'S> 



CHELTENHAM 
(50°l,3S0°Sl 



TUCSON 
<40°4. 3l2°2l 



HONOLULU 
(21°/. 266°5) 



ALIBAG 

t 9°5. I43°6 ) 



MANIL A 
< J'3, IS9°8 > 



HUANCAYO 
i,-0%, 353'S, 





J I I I I L- 



_l I I L 






FIC.106-DISTURBANCE DAILY VARIATION ( S ), DISTURBED DAYS, SUMMER , 1922 ■ 33 (GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

* NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



212 



SOOANKYLA 
(63°S, HOlO) 



L ERWICK 

(6i°s, sa?e> 



SITKA 
<60T0,2T5.°4) 



ESKDALEMUIR 
( SB?S, 62° 9 ) 



RUDE SKOV 
iSS?8,</8°Sl 



AGINCOURT 
(SS°0, 347°0) 



ABINGER 
(S4°0. 83°3) 



DE BIL T 
lS3?8,89°6) 



VAL JOYEUX 
{.S/?3, 84?S) 



CHELTENHAM 
(.50° I , 350?5) 



TUCSON 
i.40?4, 3I2°2) 



HONCL UL U 
(2I°I, 266° S) 



AL/8AG 
(3°S, I43?6) 



MANILA 
(jfj, 18ft 8 J 



HUANCAYO 
(-0l6,3S3°8) 

WA THEROO 
(-4l°8,/85°6) 



AMBERL E Y 
(-47°7,252°3) 





j — \ — i — 1_ 



l l l i i i i i i l l 

4 8 12 16 20 2 

LOCAL GEOMAGNETIC HOURS 




'■'■'■■ 



-i — i — r 

'2 



-\ — i — i — l — r 
16 20 24 





FIG.I07-DISTURBANCE DAILY VARIATION ( S D ), DISTURBED DAYS, YEAR, 1922-33 (GEOMAGNETIC LATITUDES AND 
LONGITUDES INDICATED RESPECTIVELY IN PARENTHESES) 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



213 



(+62° 5) 



( + 60 ) 



C +S5°) 



(+50°) 



{+40 ) 



i-SO ) 



4 8 12 16 20 24 






'■■■■' 



-1 — i — i — i — i — i — i — i — i — i — i — r 
4 8 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 





12 16 20 24 





FIG.IOB- DISTURBANCE. DAILY VARIATION ON DISTURBED DAYS (.%), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, JANUARY, 1922 - 33 

' NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



214 



( + 62 5) 



(+60) 



(+ 55 ) 



(- 10°) 



I -50 ) 



(-55°, 



(-60 ) 



i - 62: 5) 






t — i — f — i — i — i — ( — i — i — i — i — i — r 

4 B 12 16 20 24 

LOCAL GEOMAGNETIC HOURS 





4 a 12 16 20 24 




_l — i 1 — 1_ 



: 50 l 



FIG.I09-DISTURBANCE DAILY VARIATION ON DISTURBED DAYS (S D ), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, FEBRUARY, 1912-33 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



215 



(+SS°J 



(+50°) 



(-30 ) 



(-10 J 



(-S0°J 



(SS'j 



(-60 J 



C- 62°S) 



04 a ii m 10 a 






— i — i 1 — I 1 1 ! 1 — i — * r 

4 8 12 16 20 14 

LOCAL GEOMAGNETIC HOURS 





4 6 IS 16 20 24 




J i l l I l l. 



*°\ 



FIG. 110 -DISTURBANCE DAILY VARIATION ON DISTURBED DAYS (S D ), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, MARCH, 1922-33 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



216 



c + io"} 



( - 50 j 



(-60') 



(-6 2° 5) 






—i — i — i — i — i — i — i — i — i — i — i — r 
4 B II 16 10 24 

LOCAL GEOMAGNETIC HOURS 





fig. Ill -disturbance daily variation on disturbed days (Sq), in various geomagnetic latitudes, geomagnetic 

COMPONENTS, APRIL, 19!?- 33 
NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 






217 




fig. uz- disturbance daily variation on disturbed days (s ), in various geomagnetic latitudes, geomagnetic 

COMPONENTS, MAY, 1922-33 
o 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



218 




FIG. 1 13 -DISTURBANCE DAILY VARIATION ON DISTURBED DAYS (So), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, JUNE, 1922-33 

* NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARC DIFFERENT THAN FOR OTHERS 



219 



( + 62?S) 



l*«0 i 



<+« ) 



(+so-j 



(+P0 J 



(0°) 



i - 20') 



(-40") 



I -SO') 



(-SS ) 



(-60') 






J 1 1—1 ■ ■ ■ I I I I I L 



I I I 1—1 1 I I I I I I I 

4 e 12 It 20 24 

LOCAL GEOMAGNETIC HOURS 





ay' 
**''■*■ ■ ■ 



4 a 12 it 





6Z 



FIG. 1 1 4- DISTURBANCE DAILY VARIATION ON DISTURBED DAYS (Sq\ IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, JULY, 1923-33 

* NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



220 



(+S2°SJ 



l+ss'y 



(+20) 



< ) 



(-20 ) 



i-30) 



(-40 > 



(-so') 



(-SS-J 



i-ao'j 



(-«£s> 










t — i — i i i i i i i i — i— i — r 
4 a II IS 20 24 
LOCAL GEOMAGNETIC HOURS 





-J I— I I I I I I I I I L 



-1 1 1 I I I I 1— 

4 B 12 It 





6Z 



J I L_l I I I L_ 



r«S 



F/G. IIS -DISTURBANCE DAILY VARIATION ON DISTURBED OAYS (S ), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, AUGUST, 1921-33 

* NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



221 



<+i2.5) 



( + 60) 



( + 55 ) 



(.+20) 



(+10 ) 



(-30 J 



(-30 ) 



( - 40") 



(-55 ) 



i-e?rs) 






4 s I I L. 



T — I — I — I — I — I— I — I — I — I — I — I — r 

4 6 12 16 20 14 

LOCAL GEOMAGNETIC HOURS 




_J I ' ' i—i l ' I I i L 



-l — l — i — i — i l i l — i — r— r 
4 3 12 16 20 24 




-50 ! 



FK. 1 1 6- DISTURBANCE DAILY VARIATION ON DISTURBED DAYS (So). IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, SEPTEMBER, 1922-33 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



222 




FIG. 117 -DISTURBANCE DAILY VARIATION ON DISTURBED DAYS (Sq), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, OCTOBER, 1922-33 

* NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



223 



( + ei'si 

(+iS°) 
< + So"j 



( + 20 > 



i-SS°) 



(-60°) 



(-*2°S) 






LOCAL GEOMAGNETIC HOURS 






' ■ ' I I l ' 



' ■ I l 




— — . — i — i — ' I l ■ ■ ■ ■ 



y°i 



FIG. U8 -DISTURBANCE DAILY VARIATION ON DISTURBED DAYS (Sp), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, NOVEMBER, 1922-33 

* NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARC DIFFERENT THAN FOR OTHERS 



224 



<+6i:s> 



1 + 60} 



<+SS") 



(-50 ) 



AX 



-i — i — i — i — r— 
4 8 

LOCAL GEOMAGNETIC HOURS 






ar 



4 8 I! 16 30 24 





J 2 



r»l 



FIG. 119 -DISTURBANCE DAILr VARIATION ON DISTURBED DAYS (Sd), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, DECEMBER, 1922-33 
NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



225 



(+62° 5) 



(+60 ) 



( + 55°) 



( -20') 



(-40) 



(-50) 



( - 55°) 



( - 60') 



( - 6275) 






LOCAL GEOMAGNETIC HOURS 





ar' 



J ■ ■ 



4 a 12 IS 20 24 




A2 




' ' '.■■.■ 



r»| 



FIG. ISO-DISTURBANCE DAILY VARIATION ON DISTURBED DAYS (S ), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, WINTER, 1911-33 
NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



226 



( + e£si 



< + eo°j 



<+S0") 



i + 40 J 



( - 20") 



( - 40") 



(-SO") 



(SS ) 



<-sA) 






t — i — i — ? — i — I — i — i — I — I — i — I — r 

4 8 12 16 SO 24 

LOCAL GEOMAGNETIC HOURS 




ar' 




-so 5 



FIG, 121 -DISTURBANCE DAILY VARIATION ON DISTURBED DAY'S {So), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, EQUINOX, 1922-33 
NOTE PARTKULARLr THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



227 



(4ti?S) 

C+«e"J 

(+55°) 
(+ 50°) 
( + 40°) 

C + 30°) 
( + 20°) 
(+10°) 
<0°J 
(- 10° ) 
(-20°) 
(- 30°) 
(-40°) 
(-S0°) 
<- 55°) 
(-60°) 
<- tf.S) 






LOCAL GEOMAGNETIC HOURS 




ay' 



_l |_L 





J I— I 1—1 1—1 1—1 l—l L. 



rso | 



fig. IZZ- DISTURBANCE DAILY VARIATION on disturbed days <S d >, IN VARIOUS GEOMAGNETIC LATITUDES, geomagnetic 

COMPONENTS, SUMMER, 1912-33 

NOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFERENT THAN FOR OTHERS 



228 



( + 62° 5 J 

(+eo°j 

( + SS°) 

l + SO°) 
(+ 40°) 
(+30°) 
( + 20°) 
( + 10°) 
(0°) 
(.-10°) 
(-20°) 
(-30°) 
(-10°) 
(-S0°) 
(-S5°) 
< - 60°) 
( - 62° 'S) 






t — i — ? — i — i — i — i — i — i — i — i — i — r 

4 B II 16 20 24 

LOCAL GEOMAGNETIC HOURS 




-J I I I L 




_l I I I I 1 L- 



^50 % 



FIG. 123- DISTURBANCE DAILY VARIATION ON DISTURBED DAYS (Sp), IN VARIOUS GEOMAGNETIC LATITUDES, GEOMAGNETIC 

COMPONENTS, YEAR, 1922-33 

* VOTE PARTICULARLY THAT SCALES FOR GRAPHS IN AURORAL REGIONS ARE DIFFEREN1 THAN FOR OTHERS 



229 




riG. I24(A)-ST0RM-TIME VARIATION (E^p IN EQUATORIAL REGIONS AS GIVEN BY SAN JUAN. ALIBAG, AND HONOLULU 



230 




AS DEPARTURES FROM ANNUAL MEAN, BY SUNSPOT-ROTATIONS, SEPTEMBER I, 1932 TO AUGUST 31, 1933 



231 




232 




233 




FIG. !2S(A)-HOURLy MEAN DEPARTURES OF GEOMAGNETIC NORTH COMPONENT FROM MEAN OF APRIL 30, 1933 
(GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



234 




nCI?5(B)-ST0RM-TIME VARIATION s t) FROM SAN JUAN, ALIBAG, AND HONOLULU AVERAGE TIMES FACTOR 
(GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



235 




FK-IZSlQ- DISTURBANCE DAILY VARIATIONS (Sq) PLUS SOLAR DAILY VARIATION (S^) FROM (A) MINUS 
(GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



236 




FK. 126(A)- HOURLV MEAN DEPARTURES IN GEOMAGNETIC NORTH COMPONENT (X'\ FROM MEAN OF APRIL 30. 1933. 
STORM OF MAr 1,1933 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



237 




FIG.I28(B)-H0URLY MEAN DEPARTURES IN GEOMAGNETIC NORTH COMPONENT (x')FROM MEAN OE APRIL 30,1933, 
STORM Oh MAY 1,1933. {GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



238 



HONOL UL U 



L UKIAPANG 



ALIBAS 

(9f5) 



MANIL A 



HUANCAYO 



ELISABETHVILLE 



APIA 



BAT AVI A 
(-IT°6) 



PILAR 



TANANAPIVO 



CAPETOWN 



WATHEROO 
(-41%) 



TOOL A NCI 



AMBERLEY 



SOUTH ORKNEYS 

(-scto) 




MAY I MAY 2 MAY J 

GREENWICH MEAN HOURS 





FIG. /26(C)- HOURLY MEAN DEPARTURES IN GEOMAGNETIC NORTH COMPONENT (X 1 ) FROM ML .VV OF APRIL JO. 1933, 
STORM OF MAY I, 1933 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHH.FS) 



239 




FIG. IB6(0j— HOURLY MEAN DEPARTURES IN GEOMAGNETIC EAST COMPONENT (Y'jFROM MEAN OF APRIL 30,1933, 
STORM OF MAY 1,1933. (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



240 




I I I I I 

FIG. 126(E)- HOURLY MEAN DEPARTURES IN GEOMAGNETIC EAST COMPONENT (r'J FROM MEAN OF APRIL 30.I9SS, 
STORM OF MAY I,I9S3 (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



241 



HONOLULU 



lUKIAPANG 

U<to) 



ALIBAG 
(9°S) 



MA NIL A 
if 3) 



HUAHCAYO 



EL IS ABC TH VIL L E 



APIA 



BAT AVI A 
i-!7°6) 



PILAR 
{-20°2) 



TANANAPIYO 

i-e3°7) 



CAPETOWN 

(■aifrj 



WA THE POO 



TOOL ANSI 
i-4t°7) 



AMBERLEY 



SOUTH ORKNEYS 



i — i — I — r— i — i — r— 
OB 16 24 



— I — i — i— i — i — i i i i — i — i — i — ■ i l l i i i — i — l — i — l l l l 

It 24 B 16 24 B 16 24 B IB 24 B It 24 

MAY 2 MAY 3 MAY 4 

GREENWICH MEAN HOURS 

. .. i ■*- 



■W^ 



■ii if"i rin, m 






— *^v 



,. i l , MU gT^ M. l ,i ll i ^nfmm j 



— 5~»- 



1^ pi — <\ 



_1 I I I i— 



FIG 126(F)— HOURLY MEAN DEPARTURES IN GEOMAGNETIC EAST COMPONENT (y'J FROM MEAN OF APRIL 30,1933, 
STORM OF MAY 1,1933. (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



242 




FIG-iaS(G)-HOURLV MEAN DEPARTURES IN GEOMAGNETIC VERTICAL COMPONENT (Z) FROM MEAN OF APRIL 30,1933, 
STORM OF MAV I, I933.(G£0MAGN£TIC LATITUDES INDICATED IN PARENTHESES) 



243 



MEANOOH 
(6l°8) 



SITKA 
(60°0J 



ESKDALEMUM 



LOl/6 
(5S°I) 



SLOUTSK 
<5C?0J 



RUDE SKOV 
(SS°B) 



AGINCOURT 
(55?OJ 



ABINCER 
(5l"0J 



Of BILT 
(Sf.8) 



val joveux 
(Sl°3J 



smoER 
(Scfej 



CHELTENHAM 
(50°l) 



TUCSOU 
(40?4J 



SAM JUAN 
<!9°9J 



H£L WAN 
(ST.'sj 




^•^ 



JXr 



X/~ k 



MAY 2 MAY 3 MAY 4 

GREENWICH MEAN HOURS 



A,,.,-- 



FIG. IB6\H)-H0UHl_y MEAN DEPARTURES IN GEOMAGNETIC VERTICAL COMPONENT (Z) FROM MEAN OF APRIL 30,1933, 
STORM OF MAY" 1,1933. (.GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



244 



HUANCAYO 
(-0% 



ELISABETHVILLE 
«2°7) 



APIA 
(-igO) 



HONOLULU 
(2l'l) 



LUKIAPANO 

<2o'o> 



ALIBAC 
(9%) 



MAN /LA 
(3°3> 



BA7AI/IA 



PILAP 
<-*0?2) 



TANANAPIVO 
(■23*7) 



CAPETOWN 
(-3*7) 



WA THE POO 

trt/Te) 



TOOLANGI 



AMBEPL L y 



SOUTH ORKNEYS 



t — i — i — i — i — i — i — i — i — i — i— i— i — r 
8 '6 24 8 16 24 



16 24 8 16 24 



16 24 8 16 24 



"""%/? 



4v— ■ 



— =N^ 



MAY 2 MAY 3 

GREENWICH MEAN HOOPS 



FIG. USdh^OUHLY MEAN DEPARTURES IN GEOMAGNETIC VERTICAL COMPONENT (2) FROM MEAN OF APRIL 30,1933, 
STORM OF MAY 1,1933. (GEOMAGNETIC LATITUDES INDICATED IN PARENTHESES) 



245 



THUL£ 
(BS'O) 



GODHAVN 
(7 9° B) 



SCORESBY SUND 

(rs°s) 



SVEAGRUVAN 
(73?9J 



CHESTERFIELD INLET 
(73° 5) 



BEAR ISLAND 
(71° l) 



JULIANNCHAAB 
(70'S) 



FORT RAE 
(69° 0) 



POINT BARROW 
(68°6) 



TROMSO 
(67° I) 



PETSAMO 
(64°9> 



COLLEGE FAIRBANKS 
(64° 5) 



SODANKYLA 

(6j°e) 



LERWICK 
(62°$) 



MEANOOK 
(61-B) 



12 24 



^^r 



I! 24 



•~yr* 



-i — i — i — i — i — i — i-p — i — i — i — i — i — p 

12 24\0 12 24 

GREENWICH MEAN HOURS 



•V. 




OCTOBER 9, 1932 

I . &! . I 




6X 1 



DECEMBER 17, 1932 



FIG. 127(A) -HOURLY DEPARTURES FROM MEAN OF DAY, GEOMAGNETIC COMPONENTS ax\ 6Y 1 , AND 4Z (GEOMAGNETIC 

LATITUDES INDICATED IN PARENTHESES) 



246 



SITKA 
(SO' 0) 



ESKDALEMUW 
(SB'S) 



LOVO 

(se'i) 



S LOUTS* 
(1670) 



dude skov 

(SS-8) 



AGINCOURT 

(ssTo) 



AB1NGED 
(S4°0) 



DC BILT 
(53° 8) 



ML JOYEUX 
(Sl°3) 



SWIDER 

(so?e) 



CHEL TENHAM 

(so'i) 



TUCSOU 
(4074) 



SAN JUAN 
(It' 9) 



HE L WAN 
(I7'i) 



HONOLULU 
(Ifil) 



— V*- 



ax' 



OCTOBER 9, 1932 
I . #". . . 



GREENWICH MEAN HOURS 



rJ^ 



-_-A-. 



i i i I 



DECEMBER 17, 1932 
I M" 

J_l L— I l_ 



az 



FIG IITO-HOURLY DEPARTURES FROM MEAN OF DAY, GEOMAGNETIC COMPONENTS 6 X", AY", AND &Z (GEOMAGNETIC 

LATITUDES INDICATED IN PARENTHESES) 



247 



LUKIAPANG 
(20° 0) 



ALIBAG 

(9°S) 



MANILA 
<3°3) 



HUANCAYO 
<-0°.6> 



ELISABETHVILLE 
1^12° 7) 



APt A 

c-ie?o> 



BATAVIA 
(-17' 6) 



PILAR 
(-20?2) 



TANANARIVO 
(-21° 7) 



CAPETOWN 
(-32° 7) 



WAT HE POO 

(-4i°ej 



TOOL A HOI 
(- 46° 7) 



AMBERLEY 
(-47° 7) 



SOUTH ORKNEYS 
(-50° 0) 



t — i — i — i — i — i — r 



-i — i — i — l — rri — i — i — i — r- 

12 24\0 12 

GREENWICH MEAN HOURS 



ax' 



OCTOBER 9, 1932 
AY 1 



ax' 



DECEMBER 17, 1932 

I ar' I . 



-I I I I !_ 



FIG. 127(C) -HOURLY DEPARTURES FROM MEAN OF DAY, GEOMAGNETIC COMPONENTS 6X 1 , AY 1 , AND 4Z (GEOMAGNETIC 

LATITUDES INDICATED IN PARENTHESES) 



248 



THUL£ 

(88° o) 



GODHAVN 
(79° 8) 



SCORESBY SUND 
(7S°8) 



SVEAGRUVAN 
(73°9) 



CHESTERFIELD IHLET 
(73° i) 



BEAR ISLAND 
(71°l) 



JULIANNEHAA8 
(70° 8) 



roar rae 
(69° o) 



POINT BARROW 
(68° 6) 



TROMSO 
(67°l) 



PETSAMO 
(64°9) 



COLLEGE FAIRBANKS 
(64° 5) 



SODANKYLA 
(63° 8) . 



L ERWICK 
(62°S) 



MEANOOK 
(6I°B) 



I! 24 



AJ-~ 



^y* 



^r^ 




v^M-^V 






t~ 



Az 



♦ ■^y v ^^-v 



GREENWICH MEAN HOURS 



U \pV-A 




-^m 



r^ 



~c^ 



FEBRUARY 23, 1933 

ax' , , 1 , , ay' , , , | , , az 



^H^/ 



tf*\ 



V^ 1 



"^S^ 



^%7 




V — W 



-WW - *- -- 



r-^t 



■^v-y. 





V\j 




v^ 



,=!.«•' 






' I I I I ' I I L. 



FIG 127(0) -HOURLY DEPARTURES FROM MEAN OF DAY, GEOMAGNETIC COMPONENTS AX', AY,' AND AZ (GEOMAGNETIC 

LATITUDES INDICATED IN PARENTHESES) 



249 



SITKA 

(eofo) 



ESKOALEMUIR 



LOVO 

del i) 



SIOUTSK 
(it'Ot 



RUDE SKOV 

(ssfe) 



AGINCOURT 

(ss'o> 



ABINOER 
(J4°0) 



DC BILT 

< 53° a) 



VAL JOYEUX 
iSl'3) 



swioer 
<SO°i) 



CHELTENHAM 
(,50'lj 



TUCSON 
(40' 4) 



SAN JUAN 
(2»'») 



HELWAN 



HONOLULU 



~*v~ 



■■— ** » y ^V««A ■»' 






■ %-^v 



■ v^vi_/Vwvs 



12 14\ I! 

GREENWICH MEAN HOURS 



T 



FEBRUARY 23, 1933 

AX' I AY' AZ 

' ■ ' j ■ i i 



■N/- 



^7— 



^r 



Ktf — 



/*-- 



■ , ,!■, II ' 1^ 



i— 1 ' ' ' ' 



APRIL IB, 1933 

AX' ay' AZ 

-i—i i I ■ I I I ■ ■ i I i_Li i i i_ 



FIG. 127(E)- HOURLY DEPARTURES FROM MEAN OF DAK GEOMAGNETIC COMPONENTS AX 1 , AY 1 , AND A2 (GEOMAGNETIC 

LATITUDES INDICATED IN PARENTHESES) 



250 



LUKIAPANG 

ao'.o) 



ALIBAG 
<9°S) 



MANILA 
(J'll 



HUANCAYO 
f-Oft) 



ELISABETHVILLE 



APIA 
(-I6°0J 



BAT AY I A 
(-I7°.6) 



PILAR 
C-iO',2) 



TANANARIVO 
(-23'.7) 



CAPETOWN 
(-J2T7) 



WA THEROO 

r-4i?a) 



TOOLANGl 
C-4f.7) 



AMBERLEY 
C-47'.7) 



SOUTH ORKNEYS 
f-SOTQ) 



^ — i — i — r— i — i— t 



XvT- 



AX' 



y^- 



.. ,/-*>- 



FEBRUARY 13, 1933 
I AY' . I. 



GREENWICH MEAN HOURS 



•*V 



T—i — I — i— i — i — r 



«V. 



«A^. 



-*n-i. ■***»-, 



1 * ■ ■ * i ' I 



APRIL IB, 1933 
AY' 



ncuxn-HOuRty departures from mean of day, geomagnetic components ax', ay! and az (geomagnetic 

LATITUDES INDICATED IN PARENTHESES) 



251 



THULE 
(96° 0) 



GODHAVN 



SCORESBY SUNO 
(75° 8) 



SYEAGRUYAN 
(73° 9) 



CHESTERFIELD INLET 
(7J°5) 



SEAR ISLAND 
(71° I) 



JULIANNEHAAB 
( 70° 8 ) 



FORT RAE 
(69°0) 



POINT BARROW 
(68° S) 



TROMSO 
(67°,) 



PETSAMO 
(6A°9) 



COLLEGE FAIRBANKS 
(64°5) 



SODANKYLA 
(63°B) 



L ERwtCK 
(62°S) 



MEANOOK 
(6I°8) 



r i — r— r 



r 



7- 



t — i — i — i — r - 



12 24 



12 2410 12 

GREENWICH MEAN HOURS 



^ 




JUNE 5. 1933 

ay' I 



12 14 



*£ 



■"V 



-v 



■v 



— V 



AX 1 



AUGUST 31, 1933 

AY' 

i-i 1 i i i i i_Li i_ 



FIG. 127(G) -HOURLY DEPARTURES FROM MEAN OF DAY, GEOMAGNETIC COMPONENTS AX 1 , AY 1 , AND AZ (GEOMAGNETIC 

LATITUDES INDICATED IN PARENTHESES) 



252 



SITKA 
(60°0> 



E SKOAL EMUIR 
(S8"S) 



LOVO 

csa'.i) 



SLOUTSK 
(56°0) 



RUDE SKOV 
(SS°8) 



AGINCOURT 
(SS'.O) 



ABINGER 
(54°.0> 



OE 81 L T 
(S3°8) 



VAL JOYEUX 
(Sl°3) 



SWIDER 
<50°6) 



CHEL TEN HAM 
(50°.l) 



TUCSON 
(40° 4 J 



SAM JUAN 
(29°9) 



HELWAN 
(27? 2) 



HONOLULU 
(21' I) 



JUNE 5. 1933 
AY' 



Ao 



i — i — i — r 

12 24 

GREENWICH MEAN HOURS 



AX 1 



AUGUST 31, 1933 

ay' 



FIG.I27XH/-H0ORLY DEPARTURES FROM ME AM OF DAY, GEOMAGNETIC COMPONENTS AX', AY,' AND AZ (GEOMAGNETIC 

LATITUDES INDICATED IN PARENTHESES) 



253 



LUKIAPANG 
(20°0) 



AL /BAG 
(9°5) 



MANIC A 
O? 3) 



HUANCAYO 
(-0?6) 



ELISABETHVILLE 
(-12? 7) 



APIA 

(-ie°.a> 



BATAVIA 
(-I7?S> 



Pilar 

(-20° 2 



7ANANARIV0 
C-23T7) 



CAPETOWN 
(-32°7) 



WA THEPOO 
C-4I°8) 



TOOLANGI 
C-46?7) 



AMBERLEY 
(-47?7) 



SOUTH ORKNEYS 
C-SO'W 



JUNE 5, 1933 

ay' 

i 1 ill I I 1 L_ 



— I — i — i—i — ttt — i — i — i — r- 

12 24\ 12 

GREENWICH MEAN HOURS 



AX 1 



AUGUST 31, 1933 
AY' 



t — i — i — i — i — i — r 



FIG. lt7(I)-HOUf)t.r departures from mean of day, geomagnetic components a X\ &V', AND A2 (.GEOMAGNETIC 

LATITUDES INDICATED IN PARENTHESES) 



254 



quiet days 


90°' 60°' ' . 


»b°' 


0°' '■{ 


0° 


90°' ' 60°' 30°' ' 0° ' -30°' ' tij ' ' 60°' 
GEOMAGNETIC LATITUDE 


30°' ' 0° ' '-30° ' 


YEAR 


■ . •* 1 


l«l 


. • • ' 


' • 


»•*• 


' ' .' *■ 










. / 








































WIN TER 




■ i»» 


. 




• '. 


■ . Jj 










'jl... 








n 
















• 






-r* 


■ ' • J 


• •-•- 






< 


■s» 




* 4 


.'« 


'* » \l 










' 










SUMMER 


. ■': 


*• 


.. .. 


' ■ • 


■ A 


^V* 


■** 


. . . 


, 


— -*- 


, ' h\W* 


• • ■ 


j 


«Jb_ 


ALL DAYS MINUS 
QUIET DAYS 

YEAR 























* ' M ' 










" \ * 


*»t 


* 


























WINTER 


j 




















t 












•»» 






■ V 


• '■** 








— m- 


m 't 




■*-■ — *t 






EQUINOX 


• 


• 






. 












... 










* 


.?» 


' '- 


'• ' 


* 


* 










•' 








• * 


SUMMER 


— ~ 


**« 


■ . • • 


.. ■ • 


•V 


— r** 


-*J 






— «-V 


'"•* 


*-V 


— ■, 




■"• 


DISTURBED DAYS 

MINUS 

QUIET DAYS 














. 








• 










YEAR 












. * 










• .* * 


. * 


. . 








*i 








•s 


• 








. 


<** 






■« 




." 






. 


•»" 


s # 










; \ 










EQUINOX 












, ** 


1 . 






* K 




' . 








.«, 






• 


'.•' 












































. 












• 






























SUMMER 


• 










• # " 










••' 


,i 








i 1 1 


■i i 


ax- 


' ' 


— i — i 


1 J 1 


• • 

1 • 


ay 


> 


' ' 


i 




AZ 




• * 



EIG. 128— VARIATION WITH GEOMAGNE TIC LATITUDE IN NON-CYCLIC CHANGE FOR QUIET DAYS, ALL DAYS MINUS QUIET DAYS, 

AND DISTURBED DAYS MINUS QUIET DAYS GEOMAGNETIC COMPONENTS X" V AND Z BY YEAR AND BY SEASONS I9&-33 
(TO AVOID CONFUSION POINTS ON SEASONS ARE INDICATED ALTERNATELY BY TRIANGLES AND SQUARES) 



255 



CHAPTER DC 
FREQUENCIES OF GEOMAGNETIC FLUCTUATIONS OF VARIOUS INTENSITIES AND DURATIONS 



1. General remarks. --The present chapter is con- 
cerned mainly with descriptive statistical aspects of geo- 
magnetic fluctuations. These are considered with re- 
spect to their magnitudes and durations in various geo- 
graphic localities. 

The fidelity of response of the types of magnetic var- 
iometers customarily used at observatories is first con- 
sidered. Data on long-period changes of durations of one 
day to about one year, as indicated by range in field-val- 
ues, are next described. A short discussion is then giv- 
en of three-hourly ranges, followed by extensive treat- 
ment of short-period fluctuations having durations of a 
few minutes to less than one second. There is finally ap- 
pended a short discourse on the influence of electromag- 
netic induction on the observed character of the changes 
in the geomagnetic field. 

2. Magnetic variometers.- -Various types of magnet- 
ic variometers are in use at magnetic observatories, but 
their general principles of operation and construction are 
similar. The types in most prevalent use at present are 
those known as la Cour variometers. These record var- 
iations in D, H, and Z. Since the la Cour variometers 
are typical of most others, a short discussion of them is 
included here, summarizing general features which are 
given in more detail in standard treatises and their ref- 
erences [3]. 

Though the discussion is confined to la Cour variom- 
eters, the general principles are applicable also to many 
other types of instruments, such as compasses on moving 
conveyances and galvanometers and meters using magnet- 
systems in detecting and measuring magnetic fields. 

Included in the presentation of the theory of the var- 
iometers are the differential equations satisfied by their 
responses. The solutions of these equations when the 
impressed fields are arbitrary continuous functions of 
time are next derived. The results permit the discus- 
sion for the first time of the magnitude of certain ob- 
served micropulsations in the Earth's field detected but 
very inadequately measured. On the basis of some ex- 
perimental determinations of the responses of H-, D-, 
and Z -variometers to sinusoidal fields, a few sample 
computations are made to check the agreement between 
theory and observation. 

It is shown that the apparent large rates of change 
and amplitudes (over lOOy, \y = 0.00001 CGS unit) of 
rapid micropulsations recorded are the result of the am- 
plification, through resonance, of what are considerably 
smaller fluctuations, though accompanied for short in- 
tervals of time by high rates of change. It is also found 
that the inaccuracies of responses of la Cour variome- 
ters to fluctuations down to the smallest durations meas- 
ured, namely ten seconds, are small. 

The H -variometer shown in Figure 129 uses a small 
magnet hung on a short suspension of much greater tor- 
sion than in the case of the D -variometer. In this instru- 
ment, which has a somewhat larger housing than that of 
the D-variometer, a prism is attached with brass sup- 
ports to a bimetallic strip, for temperature compensa- 
tion. The brass supports are located less than a centi- 



meter away from the magnet but do not surround it; 
hence, little damping of the motion of the magnet would 
be expected. The free periods of oscillation of the H- 
and D -magnets vary with H, and for the instruments at 
the stations considered here will be of the order of about 
two seconds. 

Figure 130 shows a view of the la Cour D-variome- 
ter and its magnet-system. A small magnet of mag- 
netic moment about one CGS is attached at its center on 
an axle mounted at the base of a small vertical mirror. 
The mirror is affixed at its top to a fine quartz fiber 
freely suspended from a torsion-head. The housing of 
copper is at no point closer to the magnet than two cm so 
that little damping is to be expected. 

Figure 131 shows the la Cour Z -variometer and its 
magnet-system. The magnet, the mirror, and the sup- 
porting knife-edges are one piece of steel. The magnetic 
moment of the magnet is of the order 100 CGS. The knife- 
edges rest on agate supports, the magnetic axis of the 
magnet being accurately aligned horizontally. The mo- 
tion of the magnet is slightly damped as it passes between 
small vertical slots in the base carrying the agate sup- 
ports. The characteristics of the instrument with re- 
spect to damping have not been thoroughly investigated; 
the magnet when set in motion by an artificial field will 
continue to oscillate for several minutes, the free period 
of oscillation varying with Z but being of the order ten 
seconds in the case of the stations considered in this 
study. The moment of inertia of the magnet-system is 
much greater than in the case of the H- and D-magnets; 
the response of this instrument hence will be somewhat 
more sluggish to small and rapid fluctuations. 

A of Figure 132 shows a typical record for the day 
May 17, 1933, at Petsamo in northern Finland very near 
the auroral zone. The record was obtained with a la 
Cour recorder having a suitable mechanism for restrict- 
ing the record to successive narrow strips of the photo- 
graphic paper. This record shows the variations in the 
magnetic elements H, D, and Z at a time-rate of about 
180 mm per hour. Shown also in the magnetogram are 
time-marks indicated by short vertical lines recorded 
at five-minute intervals, and three successive vertical 
lines at one -minute intervals indicating the hour. With 
the use of records of this type, it is possible to measure 
durations of fluctuations as short as ten seconds when 
the record is sufficiently distinct. At most stations 
(Table 104) the scale values used are somewhat less 
than for the data of A of Figure 132, being of the order 
of five gammas per mm. 

B of Figure 132 shows a magnetogram of another 
type for the same day at Petsamo recorded at the rate 
of 15 mm per hour. 

In addition to data obtained from magnetograms of 
the foregoing kind, use has also been made of recordings 
of (dZ/dt), where t is the time, as measured by the in- 
duction produced in a coil of many turns in series with 
a galvanometer. This Mitchell-loop apparatus was op- 
erated at College, Alaska, during 1 932-. 3 and gave results 
in good agreement with findings based on magnetograms. 



257 



258 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



Records of geomagnetic fluctuations have also been 
obtained with new types of equipment such as recording 
fluxmeters and the magnetic air-borne detector [12], but 
these will be little considered here. These new devices 
permit extension of measurements to include geomag- 
netic fluctuations of higher frequencies. 

3. General theory of magnetic variometers. --In dis- 
cussing the fidelity of response of the la Cour variome- 
ters yielding the major portion of the data used in the 
present study, consideration is first given to the theory 
of variometers used in the measurement of variations of 
the geomagnetic field. 

Consider a magnet of axis A, magnetic moment M, 
and free to turn about a fixed axis B perpendicular to A. 
We suppose the magnet in stable equilibrium under the 
influence of the mechanical couple MSQ due to a steady 
component So of the Earth's field acting perpendicular 
to the plane including A and B; also a couple G due 
either to gravity, an orthogonal component of field, the 
torsion of a suspending fiber, or to a combination of 
these. For equilibrium we obtain the equation G = MSq. 
We then regard the magnet as being in a position of zero 
deflection, corresponding to the variometer's base value. 

If the field changes from So to (So + s), where s is 
a function of the time small in magnitude compared with 
So, we have 

G = M(S + s) (1) 

which is the approximate basic formula used in general 
magnetic observatory practice. This formula permits 
the determination of s when the motion of the magnet 
associated with the change in G is known, when s varies 
sufficiently slowly with time. 

If s varies rapidly with time, the motion is initially 
retarded by the effect of the moment of inertia K of the 
magnet-system. There are also retardations of motion 
due to damping caused by air friction and induced cur- 
rents in surrounding electric conductors; these retarda- 
tions are both usually directly proportional to the angu- 
lar velocity of the magnet-system about its axis of rota 
tion. The general equation of motion of a variometer 
magnet then becomes 



Kd + 2kK0 + G(0) = M(S + s) cos 8 



(2) 



where 8 is the angular displacement of the magnet in 
radians from its position of zero deflection correspond- 
ing to So- The damping factor (kir/p) is the logarithmic 
decrement per half -period. The period (2ir/p) of the 
damped oscillation is defined as the interval between 
successive instants at which 8 is a maximum, following 
the sudden application of a magnetic impulse. 

In the case of a D-variometer, the couple G(8) =MH 
sin 8, Sq = 0, and putting s = T, where T is a magnetic 
force transverse to the magnetic meridian acting in the 
direction of increasing 8, (2) becomes, when 8 is small 



K0 + 2kK0 + MH0 =MT 



(3) 



For an H-variometer, we have G(8) = C(<5 + 8 ) 
where 6 is the initial angular twist in the vertical sup- 
porting fiber required to align the magnet perpendicular 
to the magnetic meridian in the presence of the constant 
field So = Ho- In this case (2) becomes 

YL8 + 2kK0 + C8 = Mh (4) 

where 8 is small, CS - MHq, and s = h 



In the Z -variometer , the magnet is balanced with its 
magnetic axis horizontal against the couple MZq of the 
standard field or base value Zq. When Zq changes to 
(Zq + z), the balance is achieved through opposing cou- 
ples M(Hq + h) sin 8 cos p, where p is the azimuth of 
the north-seeking end of the magnet measured from the 
magnetic north around by east, and the couple mga cos 
(a - 8 ); here m is the mass of the magnet, g the ac- 
celeration of gravity, a the perpendicular distance from 
the center of gravity P of the magnet-system to a point 
O on the axis of rotation, and a the acute angle between 
the magnetic axis A and OP. Thus 

G{8 ) = MH sin 8 cos p + mga cos( a. - 8) 

so that (2) becomes 

K0 + 2kK0* + MH cos p sin 8 + mga cos (a- 8 ) 

= M(Zo + z) cos 8 

When 8 is small 

K0 + 2kK0 + [mga sin a + MH cos p]0 =Mz. . (5) 

noting that MZ q = mga cos a. 

We may rewrite (3), (4), and (5) 



8 + 2k0 + n 2 =Ms/K. 



(6) 



appropriate to a D-, H-, or Z -variometer if, respective-' 
ly we have s = T, h, or z and n 2 = (MH/K), (C/K), or 
[mga sin a + MH cos p]/K. 

We note (6) is the familiar equation of forced vibra- 
tions applicable to a system free to oscillate in one di- 
mension when retarded by a restraining force propor- 
tional to the velocity. If k = and s = 0, the magnet is 
then imagined to oscillate about its equilibrium position 
without damping and has a frequency n and period (2-jr/n). 
If n > k, k ^ 0, the frequency p is given by p 2 = (n 2 -k2) 
so that the introduction of damping lengthens the period 
of free oscillation. 

If s varies slowly with time so that 2k 8 and 8 are 
small compared with n 2 0, (6) becomes 



(Kn 2 /M) 8- = s 



(7) 



where (Kn 2 A") is the scale value of the variometer (for 
D, H, or Z, respectively, the values being H, C/M, or 
[mga sin oc+ MH cos p]/M) in CGS units per radian of de- 
flection when 8 is not too large. The scale value in gam- 
mas per minute of arc is thus 

e b = [7r/(180 x 60)] 10 5 Kn 2 /M = 29.09 Kn 2 /M. . (8) 

If a mirror properly aligned and rigidly attached to 
the magnet reflects a light beam from a fixed source on 
to a screen, (8) becomes 



e K = 10 5 Kn 2 /2dM 



(9) 



in gammas per millimeter deflection at the scale, d be- 
ing the optical distance in millimeters from the magnet 
mirror to the scale or recording drum. This value €l 
may be called the base scale value of the variometer, 
since it is the scale value at the position of zero deflection 
corresponding to the base value of the variometer. 



FREQUENCIES OF GEOMAGNETIC FLUCTUATIONS 



259 



The variation in scale value with ordinate & in mil- 
limeters is found less directly by differentiation of the 
variables entering in the unsimplified expressions for 
the couples for each variometer, where sin 8 is not re- 
placed by 8 and cos 6 not replaced by unity. We thus 
obtain 

e D = £ bD sec 2 =€ bD [l + 2 /8d 2 ] 

£ H = € bH sec 6 + 10 5 H tan 6/2d 

* e bH + 105 & E o/ 4d2 
€ Z = e bZ + 10 5 z tan 0/2d = e bz + 10 5 £z/4d 2 

in gammas per millimeter. In practice, the base scale 
value suffices for calculating deflections to the nearest 
gamma, except for rare large deflections in (H) (most 
frequently experienced in auroral regions). The deriva- 
tion of scale values and the theory of H-variometers has 
been carefully and extensively considered by George 
Hartnell [401. 

Using (7) and (9), we get (S + s) = (S + e h £). If 
the temperature varies, the magnetic moment changes, 
and 

M = M (1 - (8T) (10) 

where Mq is the moment at a standard temperature Tq, 
T the temperature, and /3 the temperature coefficient in 
gammas per degree of temperature. We then get 



(S 0+ s) =[B + i8(T-T ) + e h &) 



(11) 



where B = (Sq + £ b i'), say, the known base-line value at 
the recorder (in general provided by a light beam from a 
fixed mirror and but slightly removed from the light spot 
for zero deflection), and £' the departure in millimeters 
with proper sign from the position of zero deflection. 

The effect of change in temperature upon the values 
of n 2 and e b is small (when s is small) and is usually 
neglected; its effect is that of producing an apparent 
change in the base values Sq = (Ho, Zq) due to changes in 
the balancing couples dependent on M. We had actually 
H =CMMq{l =/3T}]=C5{l + (3t}/M , Z # mgd 
cos a[l + jQTJ/Mo, so that a correction linear with tem- 
perature is indicated. For a D-variometer, the tempera- 
ture coefficient is usually negligible. 

In (11) the impressed field s and the response are 
equivalent, since s varies slowly with time. When s 
varies rapidly with time, the remaining terms of (6), de- 
pending on the acceleration and velocity of the moving 
magnet-system, require evaluation. For this purpose, 
the constants k, n, and (M/K) may be obtained experi- 
mentally. 

The factor k is most readily found from the ampli- 
tudes of successive deflections during free oscillations 
of the magnet-system or less simply by fitting a function 
Ae~kt sin(pt +v) to a photographic record of these de- 
flections. The timing of oscillations yields the constant 
p, whence n 2 = (p 2 + k 2 ) can be calculated, and further 
permits the calculation of (K/M) using (9) when the 
scale value € b has been obtained with the aid of a Helm- 
holtz coil and milli ammeter. 

Since (K/M) from (9) is known to four figures, the 
calculation of H to the same accuracy is possible, noting 
that for the D-variometer n 2 = (MH/K), whence H = 
(Kn 2 /M). The value of H can also be obtained by a 



method used by la Cour, by arranging a Helmholtz coil 
on a D-variometer to give a horizontal field T trans- 
verse to the magnetic meridian deflecting the magnet 
through an observed angle 6 (determined from the de- 
flected beam on a screen); then since MH sin 8 = MT 
cos 8 we have H = T cot 8 . In using the latter method, 
a correction of the deflection for torsion of the suspen- 
sion-fiber is desirable and 8 should be as large as pos- 
sible. 

The values of K and M for either a D- or H-vari- 
ometer can also be obtained apart from their ratio (K/M), 
since the magnet-systems are interchangeable. When the 
magnet-system is mounted as in an H-variometer, we 
may by an oscillation experiment find p, whence also 
finding k we get n 2 = (p2 + k 2 ) = (C/K), having a value 
different from that for the magnet in the meridian. By a 
torsion experiment we next obtain C, whence K becomes 
known, since n 2 is known. Having K, we obtain M from 
the value (KAl). 

The accuracy of determination of constants is largely 
dependent on the accuracy of the milliammeter used. How- 
ever, when H is known to about five figures, we can ob- 
tain (K/M) to about five figures from the relation n 2 = 
(MH/K), (most readily when k is small) for either the H 
or D magnet-systems mounted as in a D-variometer. 

In the case of a Z -variometer, after finding k, and 
the moment M of the magnet from deflections of the mag- 
net system of the D-variometer (account being taken of 
the distribution coefficient), we may then obtain a, K, 
and a by the timing of oscillations. We have p 2 = (n 2 -k 2 ) 
when n > k, and from (6), with n 2 = (mga sin a + MHq 
cos p)/K, MHq = mga cos a. cot I, where I is the mag- 
netic dip, and MZq tan a. = mga sin a, there results 

(ng/n^) = (mga sin a + MH Q )/(mga sin a - MHq) 

= (1 + cot a cot I)/(l - cot a cot I) (12) 



whence 

cot a = (n| - n 2 ^) tan I/(n| + n 2 ^), 

K = M(Z tan a + H cos p)/n 2 , [ ... (13) 

a = MZq sec a/mg 

As before, using (9) we get 

(KAl) = (2 x 10" 5 d € b /n 2 ) (14) 

in terms of the scale value in gammas per mm when the 
distance d is also in mm. We can evidently also find e b 
from (13) and (14) by timing oscillations when Hq and 
Zq are known. 

4. Solution of the response equation. --In (6) we had 
for any unifilar variometer and standard vertical inten- 
sity balance 

(8 + 2k0 + n 2 0) = (Ms/K) 

where 8 is the angular deflection of the magnet in radians 
for the impressed field s. On writing f (t) = (MS/K) this 
becomes the equation of forced vibrations for a mechani- 
cal system free to oscillate in one dimension. Its solu- 
tion may be obtained directly from the differential equa- 
tion using the integrating factors e^ sin pt and e^* cos 
pt [41] in the form 



260 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



p0 =/* e- k(t_r) sinp(t -r)f(r) dr 
•'O 



(15) 



if 6 = 0, =0 when t = 0. If the impressed field [(K/M) 
f (t)] is arbitrary and expressible in terms of a Fourier 
series, we have 

00 

f(t) = EC m sin (mt + 6 m ) 

whence, putting u = (t - t) 

e = Z^/ %t e^ u sin [m(u + t) + £ m ]du . . (16) 
P i/q 

where a> = (k - ip) so that is the imaginary part of (16). 
However, it is likely to be found in practice more con- 
venient to calculate by numerical methods from (15). 

With the aid of Fourier integrals, a solution may also 
be obtained in the form of a contour -integral. Writing 
(6) in the form 

( + 2k5 + n 2 6 ) = 4> (t), t > (17) 

putting a) = (u + iv), we get the Fourier transform 



V§¥e (a>)=/*°° e(t)e i0)t 
J o 

(l/io,)/" 
•'O 

= - (l/io>) 0(0) - (1A) 2 ) 0(0) - (l/o) 2 ) Z" 00 0(t) e ia)t dt 

•A) 



- (1/io)) 0(0) - (1/iaj) Z* 00 0(t) e" ia,t dt 



ir$(a J )=y ,OO 0(t)e ia,t dt = / %OO ( i 



after integrating by parts. Also 

= / ~0(t)e* -v dt = /* 
'0 Jo 

= -(a>/i)0(O)-0(O)-2k0(O)- V27T(&) 2 +2kia)-n 2 )a (cu) 

Hence 

0(t) = (l/2ir)/ ,la+a> [e- ia,t /(cu 2 + 2kia> - n 2 )] 
•Aa-co 



[(2k - Ia>) 0(0) - 0(0) + $ (to)] do 



(18) 



when a is sufficiently large. This integral is evaluated 
by the method of residues, when $ (o>) obtained from 
<t> (t) is known. 

In illustration of the application of (15) suppose f(t) = 
A(l - e _vt ). Then 

= (A/p)/ ,t e- a)u [l -e-^-^ldu 
'0 

= (A/p) [{p - g(t)}/n 2 - {pe"* -g(t) + ve- kt sin pt} 

/(n 2 - 2kv + v 2 )] (19) 

where g(t) = e (k sin pt + p cos pt). The first term is 
that due to a field (KA/pM) at t = and subsequently 
maintained constant. 



When n 2 = k, as in a dead-beat galvanometer, the 
free motion is 



x = (A + Bt) e 



•kt 



where A and B are arbitrary constants. If k 2 > n the 
free motion becomes 

x = Ae" ut + Be"^ 

where u and v are roots of the equation 

(z 2 - 2kz + n 2 ) = 

so that the free motion includes two exponential terms 
decaying at different rates. 

When the response is measured, f (t) is found by 
obtaining and graphically or otherwise from 6, to 
obtain- the terms on the left of (6) ;# Suppose = c(l - 
cos mt), so that = cm sin mt, = cm cos mt. Then 
from (6) 

f (t) = (cK/M) 
[n 2 + {(m 2 - n 2 ) 2 + 4k 2 m 2 } l/2 cos (mt + v)J. . (20) 

where tan v = [2km/(m - n^)]. Here the impressed 
field yielding the prescribed response is made up of a 
suddenly impressed constant part proportional to n 2 and 
a sinusoidal part of amplitude proportional to {(m 2 - n 2 ) 2 
+ 4k z m 2 } V 2 as compared with n 2 of the periodic re- 
sponse. The proportional increase in amplitude over that 
for a perfect response is thus n 2 /|(m 2 -n 2 ) 2 + 4k 2 m 2 j*/ 2 
for the periodic part. The following table gives this am- 
plitude ratio for various values of m 2 and periods in sec- 
onds, using constants approximating those of the la Cour 
variometers. For a fluctuation of this type, of period ten 

Variation of amplitude-ratio, actual response c(l - cos mt) 

to true response, with frequency m of impressed 

field, n 2 = 10, k = 0.0165 CGS units 



Period 



(m2-n2)2 



4k2 m 2 



Ampli- 
tude 
ratio 



0.01 


62.8 


100.00 


0.00 


1.00 


0.02 


0.1 


19.8 


98.01 


0.00 


1.01 


0.07 


0.4 


9.9 


92.16 


0.00 


1.04 


0.1 


1.0 


6.3 


81.00 


0.00 


1.11 


0.2 


4.0 


3.1 


36.00 


0.00 


1.67 


0.6 


10.0 


2.0 





0.01 


100 


90.0 


40.0 


1.0 


900.00 


0.04 


0.33 


179.6 


100.0 


0.63 


8100.00 


0.10 


0.11 


179.8 



seconds or more, it is evident that the error is less than 
4 per cent (1 per cent for period 20 seconds). The lag in 
phase of the response is very slight, only a fraction of a 
degree. As resonance (m2 = n 2 ) is approached, the am- 
plitude ratio increases to 100 and the lag in phase of the 
response increases to 90°; at resonance the amplitude 
ratio is (n 2 /2km) = (m 2 /2km) = (m/2k). Thus the small- 
er the value of k, the greater the magnification achieved. 
Below resonance, the response rapidly deteriorates and 
lags behind the impressed field in phase, this lag ap- 
proaching 180° as the period of the impressed field be- 
comes very small. 



FREQUENCIES OF GEOMAGNETIC FLUCTUATIONS 



261 



The amplification through resonance suggests the use 
of H-, D, and Z -variometer magnet-systems in evacu- 
ated, nearly nonconducting containers, with the damping, 
and hence the value of k and of the period (27r/n), being 
controlled by varying the air -content within and adjust- 
ing magnets outside. An apparatus of this type could then 
be used accurately to measure tuned responses to peri- 
odic changes in the Earth's field with amplitudes of very 
small fractions of a gamma- -phenomena as yet hardly 
investigated. 

5. Experimental determinations of responses of la 
Cour variometers to various impressed fields. - -Intro- 
duction. The following sections are concerned mainly 
with a few illustrative examples of responses to periodic 
and suddenly impressed magnetic fields, measured by R. 
G. Fitzsimmons and W. F. Wallis of the Department of 
Terrestrial Magnetism. The experimental constants 
needed for the theory were also obtained, and the results 
of theory were compared with observation. These ex- 
periments were carried out under the difficulties inher- 
ent to the making of accurate magnetic measurements in 
an urban area. Although the effects of stray magnetic 
fields are at times all too evident, these effects are nev- 
ertheless thought to be generally small compared with 
the magnitudes of measured responses. 

Apparatus . The apparatus used consisted of a la 
Cour D-variometer which was employed also as an H- 
variometer, and a la Cour Z -variometer [42]. These 
variometers were mounted in the sub-basement of the 
Department of Terrestrial Magnetism. 

In the D-variometer, the magnet was suspended on a 
fine quartz fiber and was free to move about a vertical 
axis in response to magnetic changes transverse to the 
magnetic meridian. 

When used as an H-variometer, the D-variometer 
was equipped with a heavy quartz fiber and the magnet 
was held in an east-west position by the torsion of the 
fiber. In this position it responded to changes in the 
horizontal component of the Earth's field. 

The magnet of the Z -variometer, balanced horizon- 
tally on knife-edges, was free to rotate about a horizon- 
tal axis in response to changes in the vertical intensity. 

The impressed magnetic fields to which these vari- 
ometers were allowed to respond were produced by a 
cylindrical magnet (moment 337 CGS units for the D- 
and H -variometers and moment 677 CGS units for the 
Z -variometer) mounted in a hole drilled through a cylin- 
drical shaft at right-angles to the axis. The shaft was 
rotated by a synchronous motor- It was possible to reg- 
ulate the speed of rotation of the shaft, by means of a 
friction -clutch, to within 0.05 second. 

In all cases, the deflecting magnet, as mounted on the 
rotating shaft, turned within a plane perpendicular to the 
normal position of the magnetic axes of the variometer 
magnets and was located at the same height as the latter. 
The deflecting distances were so varied as to yield suit- 
able deflections. 

An optical system was arranged so that a beam of 
light reflected from mirrors rigidly attached to the vari- 
ometer magnets produced light spots upon photographic 
paper on a rotating drum. This drum was rotated so as 
to give a record with a time-scale of 10.6 mm per second. 

Procedure. --The damping-curves for the determina- 
tion of the damping -factors k of (6) were obtained by al- 
lowing the variometer magnets to come to rest after be- 
ing set in free oscillation. Responses to impressed fields 
initially zero were obtained with the turning (deflecting) 



magnet starting from rest from a position of zero de- 
flection. In the case of the Z -variometer, the recording 
light, recording drum, and turning magnet were started 
simultaneously; for the D- and H -variometers, the turn- 
ing magnet was started a second or two after starting 
the drum and recording light. 

The micropulsations sometimes found on la Cour 
rapid recorders were simulated by subjecting the vari- 
ometers to a sinusoidal field of period near that of reso- 
nance of the magnet-systems, applied intermittently at 
successive intervals of one -half minute. 

The initial response to a "square -wave " of long dur- 
ation was obtained by having the variometers record for 
a few seconds when deflected by the field of a Helmholtz- 
coil, this field being subsequently suddenly reduced to 
zero. 

A commutator consisting of 12 equally spaced sec- 
tions served to break the recorder -lamp circuit several 
times per second so that identification of the position of 
the turning magnet could be made at all times. 

Results. The following table lists the constants of the 
variometers obtained by methods previously described. 

Constants of magnet systems Nos. D31 and ZTC 
of variometers in CGS units 



Constant 


H 


D 


Z 


M 


3 


3 


55.5 


K 


0.038 


0.038 


2.39 


(K/M) adopted 


0.013 


0.013 


0.043 


eb 


5.5y/l' 


3.0y/l' 


16.1y/l' 


m 


0.701 


0.701 


2.17 


P 


3.105 


3.58 


3.83 


k 


0.0213 


0.0148 


0.0275 


n2 


12.82 


9.64 


14.67 


a 






0.013 


oc 






-157.°4 


a sin oc 






0.005 











Figure 133 shows damping-curves obtained for the 
D-, H-, and Z -variometers. Also shown are the corre- 
sponding values of the damping-factor k of e"^, the 
exponential law of decrease in amplitude with time. The 
value is least for the D-variometer and greatest for the 
Z -variometer. The values of frequency found are of the 
same order of magnitude for each variometer. 

Figures 134(A), 134(B), and 134(C) show for the D-, 
H-, and Z -variometers, respectively, the initial (a) and 
steady (b) responses to the field of a cylindrical magnet, 
rotated about an axis through its center and perpendicular 
to its magnetic axis. The responses are shown for pe- 
riods of rotation one, two, three, and four seconds, and 
"beats" are shown near X = 2. Curves (b) measured 
about ten minutes after those of (a) show a steady sinus- 
oidal response, following the exponential decay of the 
initial wave having the frequency p of the magnet -systems. 

Figures 135, 136, and 137 show more clearly than 
does Figure 134 the transitions in the character of the 
response to impressed fields at 0.05-second intervals 
with period below that of resonance. The amplitude at 
resonance is much greater than that of the impressed 
field shown at the left in each figure. 

Figure 138(A) shows the initial (a) and steady (b) re- 
sponses (after ten minutes) to impressed fields of period 
four seconds. The uneven character of the initial responses 
is probably due to a certain initial jerkiness in the torque 
obtained from the motor and drive shaft attached to the 



262 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



rotating magnet. The steady responses in D, H, and Z 
show amplitudes about 30, 25, and 20 per cent greater, 
respectively, than those of the corresponding measured 
impressed fields. In Figure 138(B) for period nine sec- 
onds, the corresponding amplitudes of response are only 
about 2, 8(?), and 3 per cent greater than the measured 
impressed fields, so that the response has now become 
fairly good and will improve rapidly as the period in- 
creases. For purposes of the present investigation, it 
is concluded that the statistics on short-period geomag- 
netic fluctuations are insignificantly affected by the qual- 
ity of response for durations greater than 10 to 20 sec- 
onds. 

Figure 139 gives the responses for suddenly im- 
pressed constant fields. 

6. Estimates of magnitudes of micropulsations in the 
Earth's field. — Near and just outside the auroral zone, 
there frequently appear micropulsations of the Earth's 
field. At SodankylU, Finland (<£ = 67°.4 N, X = 26°.6 E), 
about one hour out of every 30 shows evidence of their 
presence. They have periods of the order of two to five 
seconds. A of Figure 140 shows an example of micro- 
pulsations in horizontal intensity observed at Lycksele, 
Sweden, over an interval of about one hour. Their period 
was evidently near that for resonance of the H -variome- 
ter, so that their amplitude is greatly magnified; their 
absence from the corresponding records of the D- and 

Z- variometers suggests that their period in this instance 
may have been maintained near that of resonance for only 
the H -variometer. B of Figure 140 shows a similar rec- 
ord at Lycksele in which the pulsations are indicated ap- 
preciably only by the Z -variometer. If it is assumed that 
the results given in the table in section four above (page 
260) apply for these instruments and that resonance was at- 
tained, the amplitudes of the pulsations may be estimated 
as about one -hundredth the recorded values or about 0.04 
gamma. C of Figure 140 shows pulsations with period of 
a minute or more. 

Figures 141 and 142 (note the change in time-scale) 
give responses near resonance frequencies for both inter- 
mittent and steadily impressed sinusoidal fields. The am- 
plitudes of the impressed fields were too small to be 
indicated to scale conveniently on the diagram; they are 
estimated to be of the order one to two gammas. 

Figure 143 gives a record of artificial disturbances 
affecting, at times, the results of the foregoing experi- 
ments. 

7. Comparison of calculated responses of magnetic 
variometers with observation. — The equation satisfied by 
the response 6 to an impressed field s was previously 
shown in (6) to be 

(€ + 2k0 + n 2 0) = (Ms/K) 

For the impressed field s ■ K(l - cos mt)/M, with 
9 = £ = at t = 0, Miss CM. Martin found the solution 
to be 

6 = Ae _kt sin (pt + m) + B cos (mt + v) + l/n 2 . . (21) 

where A = (m 2 r/np), B = r, sin fi = -(pqr/n), cos v = 
qr, q = (m 2 - n 2 ), r = [l/(q 2 + 4k 2 m 2 )*/ 2 l and p 2 = 
(n* - k 2 ). 

The response X in gammas due to the impressed 
field s (in CGS units) then becomes 



X = 10 5 (K/M) n 2 



(22) 



where K, M, and n are the constants appropriate to the 
variometer used. 

Figure 144 shows for D, H, and Z, respectively, the 
computed responses near resonance (X = 1.9, 2.0, and 
1.6), for impressed fields s = cK(l - cos mt)/M. The 
values of the constant c were adjusted to give responses 
with amplitudes the same as those of the corresponding 
experimental responses of the instruments used for Fig- 
ures 133, 134, 135, and 136. The impressed fields s are 
illustrated only for the first complete cycle, and show 
good agreement with observed steady deflections pro- 
duced by the disturbing magnet at rest. 

Figure 145 gives results of .calculations made like 
those for Figure 144 but for periods (X) of four and nine 
seconds. For X = four seconds, the computed responses 
are about 30 per cent greater in amplitude than that of 
perfect response. This is mainly due to the period be- 
ing near that of resonance. The calculated defect in re- 
sponse is only a few per cent for X = nine seconds; the 
deficiency in the response thus decreases rapidly with 
increasing period, in good agreement with the results of 
the table given in section four above (page 260). 

8. Stability of magnet -system. — In the theory, it is 
noteworthy that, intimately associated with n2, there is 
the ratio K/M involving two quantities somewhat diffi- 
cult of measurement individually. Evidently the ratio 
K/M yields an important stability factor in variometer 
performance. It thus appears desirable that a magnet- 
system should be constructed of material susceptible to 
as little change as possible in K with time; the effects of 
chemical action, chipping, or other changes in contour 
should be minimized. Of equal importance is the main- 
tenance of slow and regular change in M. It seems that 
here considerable improvement might still be effected. 
For instance, some new alloys for permanent magnets 
do not appear yet to have been used in geomagnetic in- 
struments, although use has been made of Alnico. The 
high coercive force of Alnico as well as its high energy 
value promises improved stability in M. An alloy ap- 
parently not yet tried which might provide results quite 
superior in stability even to some types of Alnico is one 
of platinum -cobalt, with a coercive force about ten times 
that of Alnico and of somewhat smaller remanence [43]. 
A hard material of this type would wear slowly, thus en- 
suring more stable values of K. 

Magnets having a highly constant value of K/M might 
also be of use in simple field -instruments for measure- 
ments of the Earth's field from oscillation experiments 
alone, or from deflection experiments alone. 

The value K/M of a variometer magnet can be ob- 
tained from (14). It is suggested that estimates of the 
variation of K/M with time can usefully serve in check- 
ing the performance of suspended magnet-systems, when 
k is not too large so that n 2 can be readily obtained. 

9. Effect of change in damping on the response of var- 
iometer. - -The variometers studied experimentally here 
were found to have values of n 2 of the order of ten. A of Fig- 
ure 146 shows the responsesfor a suddenly impressed field 
of unit strength for various values of damping-factor k. 

When k = 0.0165, which is roughly the magnitude 
found for the variometers tested, the response consists 
of a damped oscillation, decaying slowly with time, about 
the value 0.01 CGS unit. As k increases, the response 
improves, becoming best for a value slightly less than 
that for the dead-beat condition (k = 3.162). 

B of Figure 146 shows the ratio of amplitude of the 
observed to impressed fields, when the observed field is 



FREQUENCIES OF GEOMAGNETIC FLUCTUATIONS 



263 



of the form c (1 - cos mt), for various values of the fre- 
quency m. The computed effect of resonance is most 
marked for k = 0.0165 for which the amplitude ratio rises 
to 72.8. As in A of Figure 132, the response is best for 
k = 2.236. 

C of Figure 146 shows the angular lag in phase for 
the same fields as mentioned in connection with B of 
this figure, as a function of frequency m. For fields of 
period greater than about four seconds, the lag in phase 
is very slight when k = 0.0165, but as much as 30° for 
k = 2.236. This lag in phase, however, is less than one- 
half second for periods greater than four seconds and 
therefore seldom would be significant in practice. A 
value of k greater than one but less than n would thus 
result in improved performance of the la Cour variome- 
ters. Although a small value of k such as that ordinar- 
ily used may yield a trace more highly serrated, a few of 
these small periodic fluctuations appear magnified in am- 
plitude and the base scale value does not apply. A value 
of k in excess of unity would hence appear desirable. 

In the next section, discussion will relate to data on 
geomagnetic fluctuations measured with variometers the 
same as or similar to those just described and will be- 
gin with consideration of fluctuations of relatively long 
duration or period. 

10. Survey of world-wide distribution of ranges with 
time in magnetic elements, horizontal intensity (H). dec- 
lination (D). and vertical intensity (Z) .--In this section 
there are considered results relating to the world-wide 
distribution of daily ranges of magnetic intensity. 

The daily range in the magnetic elements varies in a 
marked way with geographical position. In two narrow 
zones near geomagnetic latitudes roughly 67° north and 
south, large daily ranges in H, D, and Z occur most 
frequently and with highest intensity. These are the so- 
called auroral zones, and the magnetic conditions therein 
tend to dominate those observed elsewhere, even to some 
extent those in the equatorial regions. There is also a 
tendency toward symmetry in geomagnetic disturbance 
fields relative to the geomagnetic axis and equator, and 
to the auroral zones. The geographical distribution of 
magnetic disturbances is thus conveniently studied by 
selecting stations in various geomagnetic latitudes, neg- 
lecting small differences due to longitude except in re- 
gions near the auroral zones. 

The asymmetries of disturbance in longitude are most 
marked in auroral regions where the differences between 
geomagnetic local mean time and geographic local mean 
time are greater. The major asymmetries arise because 
the auroral zone is not a circle of geomagnetic latitude 
but actually an oval. Other very slight asymmetries in 
longitude appear, due to noncoincidence of the Earth's 
geomagnetic and geographical axes. 

Table 105 lists selected stations of the Second Inter- 
national Polar Year, August, 1932, to August, 1933, pro- 
viding data for high latitudes as well as for middle and 
low latitudes. It gives the positions of the selected sta- 
tions in terms of both geographic and geomagnetic co- 
ordinates. Geomagnetic co-ordinates of position are 
measured from the point (latitude <j> = 78°. 5 N, longitude 
X = 69°.0 W) as pole (serving also as the pole of refer- 
ence for geomagnetic time), and is the point where the 
axis of uniform magnetization intersects the Earth's 
surface. At any point on the Earth, the angle ■>]/ is the 
angular difference in direction between the geographic 
and geomagnetic meridians, positive when measured 
from north around by east. Also given in Table 105 is 



the approximate magnetic declination, D, at each station. 
The positions of the selected stations are included among 
others in Figure 147. 

Figure 148(A) gives frequencies of daily ranges in H 
for the 12-month period of the Polar Year, 1932-33. The 
corresponding distributions for D and Z are given in 
Figures 148(B) and 148(C). 

The largest ranges tend to occur more frequently in 
high latitudes, especially in the region near the auroral 
zone, as shown by the stations Tromso", Petsamo, Fort 
Rae, and Sodankyla (Fort Rae is usually slightly inside 
the zone of maximum auroral frequency and Sodankyla a 
few hundred kilometers outside). Near the center of the 
auroral zone, as shown by results at Thule, the ranges in 
H and D are of nearly equal intensity and their frequency 
distributions are somewhat similar, while the daily ranges 
in Z are of somewhat lesser intensity. 

The frequency distribution at Thule could probably be 
fairly readily fitted by one of the Poisson type. This type 
of frequency distribution applies in the case of large num- 
bers of trials for which the probability of the occurrence 
of a single event is small. 

The largest fluctuations of the Earth's field are due to 
intense electric currents in the atmosphere flowing along 
the auroral zone, the circuit probably being completed by 
a current-sheet flowing towards the Sun and across the 
polar cap. The measured values of gross magnetic fluc- 
tuations at Thule thus tend to respond to average condi- 
tions near the auroral zone. Fleeting and patchy areas 
of varying ionization near the auroral zone, due to incom- 
ing groups of charged solar corpuscles, may be the cause 
of many of the rapid small pulsations in current. The 
main flow of current may hence be diverted due to changed 
electric conductivity or electromotive forces in the air in 
ionized regions. It seems likely that the return flow then 
takes place mainly in the form of broadly distributed cur- 
rent-sheets inside and outside the auroral zone. The mag- 
nitudes of the ranges attain a maximum in H and D near 
the auroral zone. The daily ranges in Z, although large 
near the auroral zone, are probably greatest on an aver- 
age just inside and outside the zone. Just outside the au- 
roral zone, the ranges decrease very rapidly with de- 
creasing latitude and then remain relatively small through- 
out low and middle latitudes. 

Figure 149 shows lines of equal auroral frequencies 
as derived by Vestine for the Northern Hemisphere. It 
will be noted that the auroral zone expands equatorwards 
from time to time. Large magnetic disturbances or storms 
are closely associated with such expansions of the auro- 
ral zone. 

The preceding results, derived mainly from data of 
the Polar Year, 1932-33, were obtained in a year near 
the sunspot minimum and hence for a period less dis- 
turbed magnetically than the average of the sunspot-cycle. 
Frequency distributions of daily ranges in magnetic in- 
tensity will now be taken over much longer intervals of 
time and compared with those obtained for the Polar Year. 
Figure 150 shows the frequency distribution of daily 
ranges in H and Z at Sitka for the 22 years from 1905 
to 1926. Shown also are the corresponding values for the 
Polar Year multiplied by 22. It will be noted that the 
frequency distribution obtained for the 12-month period 
of 1932-33 corresponds well with that found for the much 
longer interval of time. Figure 151 shows a similar com- 
parison made in the case of Cheltenham with similar good 
correspondence in values. However, it would appear that 
the correspondence is best for small ranges and that a 



264 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



single year of observation forms too small a statistical 
sample to permit discussion of very large daily ranges 
at times of severe magnetic storm. 

Figure 152 gives the frequency distribution of ranges 
in H, D, and Z at Sloutzk (near Leningrad) for the 62- 
year period 1878 to 1939. At Sloutzk magnetic storms 
have been selected by Benkova according to a definition 
that at that station a magnetic disturbance becomes a 
magnetic storm if the daily range in D is greater than 
60y. Included also in Figure 152 is the frequency dis- 
tribution of ranges at Bombay during 1882 to 1905 de- 
rived by Moos from a catalog of magnetic storms. These 
data provide information respecting the probability of oc- 
currences of magnetic storms in other regions, since 
such storms are world-wide in their incidence. Hence 
their frequencies and probabilities of occurrence can be 
conveniently examined using data for only one or two 
suitably selected magnetic stations. 

The monthly variations in frequency distributions of 
daily ranges in horizontal and vertical intensities, as de- 
rived for Cheltenham during 1905 to 1930, are illustrated 
in Figure 153. It will be noted that the variation in dis- 
turbance with season is not marked, although larger 
ranges appear with greater frequency near the equinoxes. 

Table 106 gives the probabilities for daily ranges in 
excess of various assigned magnitudes estimated from 
the data of Figures 148(A), 148(B), and 148(C) for the 
year 1932-33. The reciprocals of these values are given 
in Table 107 and provide estimates of the expectations, 
in days, of daily ranges in H, D, and Z in excess of 
various assigned magnitudes. 

Table 108 shows the observed cumulative frequencies 
and the computed expected frequencies per year, and 
probabilities and expectations, in days, for ranges in 
magnetic intensity in excess of various magnitudes. 
Since the ranges in the magnetic elements vary with geo- 
magnetic latitude, the probabilities for ranges in excess 
of given magnitudes vary with different stations. As is 
also shown by the data for Figures 150, 151, and 152, the 
expected frequencies for storms of given range vary 
from station to station. 

The results of Table 108 were included with those de- 
rived from Tables 106 and' 107 in constructing Figures 
154 and 155. From Figure 154 it appears that ranges as 
great as, or greater than 50y occur daily, or at least ev- 
ery few days, at all stations from pole to pole. While 
ranges in excess of 300y are unlikely to appear in low 
and middle -latitude regions between the northern and 
southern auroral zones, such ranges do appear in the 
latter regions at times of great magnetic storm of which 
there was no example during the year 1932-33. Near the 
auroral zone, as shown particularly by the stations 
Tromso and Petsamo, there is considerable probability 
of daily ranges greater than 1200y in H and Z. The 
same is true for a considerable region inside the auro- 
ral zone. 

Figure 155 shows the variation with geomagnetic lat- 
itude of the expection, in days, of ranges in H, D, and Z 
in excess of 50y, lOOy, 150y, 200y, 500y, and lOOOy. 
These results are derived from Tables 106 to 108, and 
as it is assumed that there is symmetry relative to the 
Earth's geomagnetic axis and equator, the results for the 
Northern and Southern Hemispheres, based on data for 
both hemispheres, give, in the case of each component 
and assigned range, curves reflected in latitude relative 
to the position of the geomagnetic equator. Since large 
values of expectations, in days, result from probability 



calculated on the basis of very small numbers of the 
total cases, they are in general highly uncertain; for this 
reason, expectations in excess of 250 days are not shown. 
However, it will be noted that the expectations derived 
from the longer series of data for magnetic storms give 
results which are in very rough general agreement with 
those found for the year 1932-33. 

Using the results of Figure 155 (in which no attempt 
was made to adjust the data for the variations in the po- 
sition in the auroral zone with longitude), a rough and 
tentative estimate has beeir made, and presented in the 
form of isochronic lines in Figures 156 to 161, for 
ranges in excess of 200y and lOOOy for H, D, and Z. 
Useful in constructing such figures are the maps of Fig- 
ures 147, 162, and 163. These data, roughly adjusted to 
the auroral zones, afford expectations, in days, strictly 
applicable only to daily ranges. For longer intervals of 
time they afford, therefore, an estimate of average upper 
limit of expectation. It may be remarked that, except for 
large ranges, the statistics for daily ranges afford prac- 
tically the same result as do those for longer intervals 
of time. 

The daily ranges in H, D, and Z are in general 
smaller than those for longer periods of time, such as 
those for several days, week, month, and year. It not 
infrequently happens, however, that the maximum weekly, 
monthly, or annual ranges in an element may be those ob- 
tained for single days of magnetic storm. 

It should be carefully noted that the maximum ranges 
for shorter intervals of time vary to a much lesser de- 
gree than do the mean annual ranges. It is then reason- 
ably certain that the frequency distribution for daily 
ranges differs from those for longer intervals of time. 
The nature of these frequency distributions will be dis- 
cussed in sections 11 to 13. 

Figures 164, 165, and 168 for Sitka, Alaska, illus- 
trate for the Polar Year, 1932-33, the variation from day 
to day in the maximum and minimum values of H, D, 
and Z, respectively, relative to arbitrary values used 
as zero. It will be noted that the successive daily ranges, 
as indicated by the differences between corresponding 
maximum and minimum values, are evidently correlated 
with each other. Small values of daily ranges are likely 
to be followed by small values, and large values by large 
values. Thus, as in the case of most geophysical data, 
the time series of the quantities which interest us show 
positive conservation. Hence the statistical probabilities 
and expectations derived in the present report relate to 
events averaged over considerable intervals of time. 

11. Survey of weekly, monthly, and yearly ranges in 
m agnetic fluctuations . — The survey of the world-wide 
distribution of ranges with time in geomagnetic elements, 
continues with discussion of weekly, monthly, and yearly 
ranges. Statistics respecting the frequency of various 
magnitudes of range in the magnetic elements for inter- 
vals longer than a few days are necessarily based on 
somewhat scanty data. Considerable difficulty conse- 
quently has been experienced in preparing the present 
survey because the number of years of operation of most 
magnetic observatories is too short. A statistical treat- 
ment of ranges in the magnetic elements is also greatly 
complicated by the lack of random character of the data. 
The data are classed statistically as conservative in 
character, meaning that large ranges tend to be followed 
in succession by additional large ranges and small ranges 
by successive small ranges. These two factors have con- 
tributed greatly to the difficulty of the preparation of the 



FREQUENCIES OF GEOMAGNETIC FLUCTUATIONS 



265 



isochronic charts presented later and complicate their 
interpretation in practical applications. It has been ne- 
cessary to draw some of these isochronics in accord- 
ance with general considerations and personal judgment, 
especially in the region inside the auroral zone where no 
magnetic observatory has ever operated over a consider- 
able length of time. 

12. Tables of probabilities and expectations of ranges 
in magnetic elements. - -The published data on maxima 
and minima in the geomagnetic elements at the stations 
listed in Table 105 were used to obtain the weekly, month- 
ly, two-, three-, four-, six-, and twelve -monthly ranges 
in H, D, and Z. The data were considered in two sets. 
The first set comprised the data for the Polar Year, 1932- 
33, permitting fairly satisfactory statistics for ranges 
during intervals as long as a week. The remaining set 
consisted mainly of data for the stations Tromso - ($ = 67°), 
Sitka ($= 60°), Cheltenham ($= 50°), and Honolulu ($ = 
21°); the results for these stations were supplemented 
by those for a 62-year interval for Sloutzk ($ = 56°) and 
for a 34-year interval for Bombay ($ = 10°). There are, 
of course, additional data available for other stations for 
many years but unfortunately it would be necessary to 
have access to the actual magnetograms, since values of 
the daily maxima and minima in magnetic elements have 
not been published for most stations except in recent 
years. Wherever possible, use has been made, however, 
of data for recent years when they appeared likely to be 
helpful. 

Table 109 lists the probabilities of weekly ranges in 
excess of various assigned magnitudes in gammas. 
These data supplement those of Table 106 in which cor- 
responding probabilities are presented for daily ranges 
in the magnetic elements. 

Table 110 gives the average probabilities of ranges 
over various intervals as long as a year for the four sta- 
tions Tromso, Sitka, Cheltenham, and Honolulu. It is no- 
ted that the probabilities of large ranges are greatest 
near the auroral zone. It further appears that the prob- 
abilities of ranges in excess of a given magnitude tend to 
diminish slightly as the interval of time for which the 
range is derived increases. This curious finding is a 
result of the tendency for large ranges during short in- 
tervals of time being followed by other similar large 
ranges; in other words, it is due to the fact that the 
ranges show a considerable degree of serial correlation. 

Tables 111 and 112 give the average expectations for 
various intervals of time for ranges in excess of various 
magnitudes in H, D, and Z. These expectations are 
calculated as the reciprocals of the probabilities in Ta- 
bles 109 and 110. The features previously noted in the 
tables of probabilities again appear. The calculated in- 
terval of time elapsing before a range is exceeded or at- 
tained during a prescribed time interval becomes longer 
with longer time interval. In the case of random data, 
the longer the interval of time elapsing, the greater would 
be the expected frequencies per interval for large ranges. 
For instance, from Tables 111 and 112, a weekly range 
in H of lOOOy or more is expected, on an average, in 
one out of every 18 weeks, whereas the three-monthly 
range of this magnitude or greater is expected in one out 
of every two three-month intervals. The point is that one 
can sometimes find in a three-month interval more than 
one range in H greater than lOOOy, although only a sin- 
gle (total) three-monthly range is taken. 

The probabilities of daily and weekly ranges in H, D, 
and Z in excess of various magnitudes are shown in 



Figure 167. The probabilities for ranges during longer 
intervals of time are illustrated in Figure 168(A), (B), 
(C), and (D). 

13. Isochronic charts showing expectations of ranges 
in H. D f and Z.- -In order to make the foregoing data 
more readily applicable for practical purposes, an at- 
tempt has been made to estimate the positions of iso- 
chronic lines drawn on world charts to show the expected 
times elapsing before ranges of various magnitudes are 
exceeded or attained. Figure 169 shows the isochronic 
lines giving the expected number of three-month periods 
elapsing before the three-monthly range in H exceeds 
500y (five milligauss). Throughout a belt nearly 2000 
miles wide on either side of the auroral zone, it is ex- 
pected on an average that there will be experienced dur- 
ing every three-month period a range in H greater than 
or equal to 500y. From the center of Greenland and 
northwards to the geomagnetic north pole, only one out of 
three three -month intervals is expected on an average to 
experience a range in H exceeding 50Gy. The isochron- 
ic line for four three-month periods passes through 
northern England; this means that in one out of four 
three-month intervals the prescribed range will be ex- 
ceeded. It is found that in low latitudes only one out of 
every 20 or 30 three -month intervals is expected to have 
a range in H greater than 500y. Figures 170 and 171 
present the corresponding isochronic lines for D and Z. 

Figures 172, 173, and 174 give the isochronic lines 
showing the expected number of weeks elapsing before 
the weekly ranges in H, D, and Z exceed lOOOy (ten 
milligauss). Figures 175 to 186, inclusive, give the iso- 
chronic lines for various intervals of time in excess of a 
week for ranges in H, D, and Z in excess of lOOOy. These 
charts are based on less satisfactory data than are those 
for ranges in excess of 500y because the frequency of oc- 
currence of ranges of lOOOy is much less than that for 
ranges of 500y in most latitudes. In fact, for D and Z, no 
example has ever been found of the occurrence of a range 
as great as lOOOy in low and equatorial latitudes. In im- 
mediately adjacent regions, magnetic data for about 25 
years reveal only one case of ranges in D and Z of this 
magnitude so that reliable statistics respecting frequen- 
cies are not available. In view of the limitations of the 
data, it is important to know that the isochronic charts 
for ranges in excess of lOOOy are in some respects rath- 
er tentative, but should on the whole have a fair degree of 
reliability. 

Figures 187 and 188 give the isochronic lines in terms 
of three -month periods for three -monthly ranges in H and 
D in excess of 1500y, as estimated from somewhat scanty 
data; in the case of Z, a range as great as 1500y was not 
found in any latitude. 

Figures 189, 190, and 191 give the regions (indicated 
by hatched lines) in which the probability is at least one- 
tenth that the total range during any average three-month 
period will exceed lOOOy. There are no regions in which 
the probability is 0.1 that the total range in H, D, or Z 
during an average three-month period will exceed 1500y. 

14. Survey of short-period magnetic fluctuations. -- 
The present study, dealing with geomagnetic fluctuations 
of durations from ten seconds to ten hours, continues the 
discussion of fluctuations persisting for various periods 
of time. 

Early results on the study of short-period magnetic 
fluctuations include Balfour Stewart's observation [44] 
that magnetic records show numerous trains of more or 
less regular waves or pulsations of period about 30 seconds. 



266 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



Kohlrausch [45] noted a fluctuation of period 12 seconds 
by eye readings of a magnetometer. Arendt [46] studied 
fluctuations of a period of several minutes in connection 
with studies of thunderstorms. Eschenhagen [47] noted 
a maximum near noon in the frequency of fluctuations of 
30 seconds' duration. Birkeland [48] found frequent 
groups of waves of periods of about 10 and 30 seconds. 
Using records for three observatories, van Bemmelen 
[49] found that trains of waves or magnetic pulses ap- 
peared more frequently near midnight at Batavia and Zi- 
ka-wei, and in the daytime at Kew. Terada [50] made an 
extensive study of magnetic fluctuations observed during 
a four -year period at the station Misaki. He hoped to 
correlate the fluctuations with earthquakes. The sensi- 
tivity of the variometers used was about 0.2 gamma per 
mm in the north, east, and vertical components. The 
magnets were from two to four cm long, approximately, 
and about two mm thick, so that the response to fluctua- 
tions of periods less than 10 to 20 seconds would not be 
good. He noted that pulsations varied in period from 
about 20 seconds to nearly one hour. During the daytime,, 
he found that fluctuations of 30 to 60 seconds predomina- 
ted, whereas those of 90 to 150 seconds appeared more 
frequently at night. He also noted a reduction and phase - 
retardation of about one -quarter period in Z as com- 
pared with H, and that the disturbing field usually yields 
a vector rotating with time. He suggested that the fluc- 
tuations probably were due to the more or less vertical 
oscillation of limited portions of layers of the upper at- 
mosphere, where incoming aggregations of particles 
from the Sun affect the electric conductivity. 

In the present study, these earlier findings, which 
were based usually on single stations, are extended, us- 
ing more homogeneous data of the Polar Year, 1932-33. 
During the average day, a marked maximum in frequency 
is found for a duration of about 50 seconds, although the 
largest amplitudes appear for fluctuations enduring from 
one to several hours in all latitudes. The latitude dis- 
tribution of the fluctuations has been roughly estimated. 
It is found that there is a marked maximum in the am- 
plitude of these small fluctuations near and just inside 
the auroral zones. In these regions the fluctuations are 
of larger magnitude in the horizontal component and 
least in Z . In low and middle latitudes the number of 
fluctuations of appreciable intensity is sharply reduced, 
and they seldom appear in Z. At times of magnetic 
storm (defined as days for which magnetic character - 
figures K exceed five — a few days per year), marked 
fluctuations, both local and world-wide, may appear in 
all components in lower latitudes. 

Rates of change up to about ten gammas per second 
in the horizontal component have been observed at such 
rare intervals as once in several years during severe 
magnetic storms in almost all latitudes. In equatorial 
regions rates of change in Z as great as ten gammas 
per second have never been observed and probably sel- 
dom if ever occur. In auroral regions, there appear 
some thousands of examples per year of rates of change 
of the order of one gamma per second, enduring usually 
for intervals of less than one or two minutes. In low and 
middle latitudes, the number is very sharply reduced, 
especially in Z; only a few examples per year of rates 
as great as one gamma per second appear even in the 
comparatively high geomagnetic latitude of Copenhagen. 
The short-period fluctuations near the equinoxes appear 
to be about twice as numerous as near the solstices. 
Their frequency appears to be more closely correlated 



with sunspot number than with certain measures now in 
use for magnetic activity. 

At times of storm, the numbers of small fluctuations 
do not show a marked variation with time of day. On or- 
dinary days, fluctuations of duration less than one minute 
are, on the average, most numerous near local noon; 
those of longer duration tend to be more numerous in the 
early morning and late afternoon or evening. 

Pulsations or fluctuations of durations greater than 
ten seconds frequently appear simultaneously in both the 
Northern and Southern Hemispheres. Ordinarily they ap- 
pear in series or groups, sometimes in superposedform. 
In their usual complex form they are difficult to trace 
from station to station. In the case of seven isolated ex- 
amples of about ten-minute duration, appearing on days 
in other respects magnetically quiet, their incidence ap- 
peared world-wide, though of very small amplitude in 
low latitudes. The disturbance caused by such fluctua- 
tion is most marked in the region near and inside the au- 
roral zone, where regularities and patterns of field can 
be fairly readily traced from station to station. 

Studies of vector diagrams of fluctuations in polar 
regions strongly suggest that the relatively small ampli- 
tude of fluctuations in Z in low and middle latitudes is 
due to earth currents opposing the external field of the 
high-latitude electric currents causing the fluctuations, 
and almost nullifying the external field in Z . These 
earth currents augment the field at the Earth's surface 
in the case of H, so that small fluctuations in this com- 
ponent are more readily recorded in low latitudes than 
are those of greatly reduced amplitude in Z; the number 
of fluctuations in H and Z is of course the same. 

The current sytems of small fluctuations sometimes 
resemble those for the polar part of the electric current 
system of magnetic storms, though greatly diminished in 
intensity. They no doubt contribute a principal part of 
the fluctuating earth currents by induction, especially in 
surface layers of the highly conducting oceanic areas. 

Although the oceans are somewhat ill-connected, they 
comprise most of the surface area of the Earth. It is 
likely that the induced electric currents due to short- 
period magnetic fluctuations could readily be calculated, 
with but slight modification of the existing theory used in 
estimating the Earth's internal electric conductivity from 
longer -period magnetic variations. 

Fluctuations in the region between those of "atmos- 
pherics" which show electromagnetic waves with periods 
up to 10 _ 4 second and those of pulsations of the order of 
one second have never been investigated. The develop- 
ment of new methods of measurement by H. Aschenbren- 
ner and G. Goubau [51] may yield a useful experimental 
approach. F. Schindelhauer [52] has discussed various 
features of atmospherics. 

Studies by van Bemmelen, Eschenhagen, Rolf, Sucks- 
dorff, Harang, Lubiger, la Cour, and others reveal that 
in addition to the fluctuations just discussed, there ap- 
pear others of distinctly local character. In auroral re- 
gions very rapid fluctuations of duration less than one or 
two seconds are noted [53]. Very regular sinusoidal 
pulsations of local character having periods of some sec- 
onds to several minutes [54, 55] also occur in auroral 
regions, and sometimes in low and middle latitudes. 

Large fluctuations known as bays, most marked in 
polar regions, with durations about one to five hours, ap- 
pear a few hundred times per year. They are world-wide 
in incidence. In low and middle latitudes their amplitudes 
are in general small, sometimes smaller than fluctuations 



FREQUENCIES OF GEOMAGNETIC FLUCTUATIONS 



267 



of shorter duration. They appear to result from a 
marked intensification of the current system responsi- 
ble for the disturbance daily variation, and hence show 
morning and evening maxima in frequency at nearly all 
stations [3, 56]. 

New data on magnetic fluctuations of short duration 
were obtained for the present volume from data of the 
Polar Year, 1932-33. Nearly all data were measured 
from microfilm reproductions of magnetograms. These 
were studied with the aid of microfilm projectors yield- 
ing enlargements on a screen at three times natural size. 
Table 104 gave the stations used and their particulars. 
Their locations were given in Figure 147. 

A fluctuation of the geomagnetic field was regarded 
as a departure of the field from a normal undisturbed 
value, followed by a subsequent recovery. In general, 
no distinctions were made respecting the sign of a fluc- 
tuation, as represented by an increase or decrease in 
field with time. It frequently happened that several fluc- 
tuations appeared together in superposed form. In this 
event attempts were made to separate the component 
fluctuations, their durations and amplitudes being entered 
separately in records of the various classes of fluctua- 
tions. The duration of a fluctuation was taken as the time 
from the beginning of the departure of field from normal 
up to the time of recovery. The amplitude is the maxi- 
mum departure from the normal value. 

In the accompanying tables or graphs, showing rates 
of change and durations of fluctuations at various stations, 
the rate of change recorded is the maximum appearing 
between the time of beginning and maximum of the fluc- 
tuations and also between the maximum departure and 
the end of fluctuation, irrespective of the sign of the fluc- 
tuation. In all cases an attempt was made to measure a 
maximum rate of change consistent with the general 
smoothed trend of the fluctuation. Some difficulties were 
experienced in a number of special cases due to the in- 
cidence of small superposed departures with greater 
rates of change, but in general these were readily sepa- 
rated from the fluctuation under consideration. The du- 
ration in the case of fluctuations studied with respect to 
maximum rate of change was defined slightly differently 
from that used in discussing the amplitude of fluctuations. 
For rates of change of fluctuations, the semidurationwas 
used as measured by the interval between beginning of 
the fluctuation and its maximum departure in amplitude, 
or from the time of maximum amplitude to the time of 
ending of the fluctuation. 

Figure 192 shows the frequency of fluctuations of 
various amplitudes at Petsamo for the period August 1, 
1932, to October 31, 1932. The observed frequencies of 
fluctuations of amplitudes lOy, 20y, ... 70y are totaled 

for durations in seconds, 0-20, 21-40, , in H, D, and 

Z, and plotted for the center of each interval. During the 
92-day period, marked fluctuations of amplitude Oy to 
lOy appear most frequently. A maximum in frequency 
is shown by durations of about 40 to 50 seconds in H, D, 
and Z . Fluctuations of larger amplitude were measured 
most frequently in the case of H and least frequently in 
the case of Z . In the case of very small fluctuations of 
Dy to lOy, the number found is to some extent affected 
by the sensitivity of the variometer. In the case of D, 
this sensitivity was 4 y/mm as compared with 13 y/mm 
for H and 20 y/mm for Z. If greater sensitivities had 
been available for H and Z, it is likely that distribu- 
tions more nearly similar to those for D would have 
been obtained. It will be noted that the three -month 



period provided insufficient data for defining clearly the 
frequency distribution for amplitudes of 50y to 80y. 
These results agree well with those of Terada for Misaki 
although his frequency distribution shows a smaller rel- 
ative number of fluctuations for intervals to 30 seconds 
than does Figure 192. This is possibly due in part to the 
longer periods of oscillation of the magnets used by Te- 
rada. 

Figure 193 gives the frequency distributions of fluc- 
tuations with various rates of change and durations at 
Petsamo for the period September 1, 1932, to August 31, 
1933. A pronounced maximum in frequency occurs in all 
elements for semidurations of 20 to 30 seconds, and thus 
in good agreement with results of Figure 192. These 
measurements extend over a longer period than was used 
in deriving Figure 192 and show greatest frequencies for 
H and least for Z. 

The results for Petsamo, near the auroral zone, may 
be compared with those for Copenhagen, a station in mid- 
dle latitudes, shown in Figure 194, for the same interval 
of time (note the change in frequency scale and also in 
the scale for rate of change). In the case of Copenhagen, 
a very extensive compilation was made in order that 
greater certainty might be ascribed to measures of semi- 
durations less than 20 seconds. It also appeared desirable 
to obtain the relative frequency of the rate of one gamma 
per second, on a significant basis, for comparison with 
Petsamo. A marked decrease with latitude is shown in 
the magnitude of the rate of change (Tables 113 and 114) 
by the data from the two stations. 

At both Petsamo and Copenhagen, the largest number 
of fluctuations in H, D, and Z appear with semidurations 
of about 20 seconds. The following table gives a compari- 
son of the total number of fluctuations per year for various 
rates of change, irrespective of duration, noted at Pet- 
samo and Copenhagen. No example of a rate of change as 
great as ten gammas per second was noted at either sta- 
tion. For slower rates of change, the effect of change of 
latitude is marked; for instance, for one gamma per sec- 
ond, there were in H 3,786 cases at Petsamo as compared 
with only 58 at Copenhagen. An additional noteworthy fea- 
ture is the marked decrease in the rate of change of Z 
from Petsamo to Copenhagen. 

Fluctuations for various rates of change for H, D, and Z 
Petsamo and Copenhagen, September 1, 1932, 
to August 31, 1933 



Rate of 
change 
y/sec 


Observation 


Petsamo 


Copenhagen 


D 


H 


Z 


D 


H 


Z 



0.1 








47,596 


19,233 


242 


0.2 








21,884 


16,188 


58 


0.4 








2,875 


2,490 


7 


0.6 








319 


282 





0.8 








162 


89 





1 


3,786 


3,769 


1,442 


58 


13 





2 


1,180 


471 


595 


3 


3 





4 


221 


58 


143 





1 





6 


39 


14 


28 


1 








8 


19 


15 


10 


1 








10 





















A very rough survey of the fluctuations at stations in 
other latitudes suggests that the results for Copenhagen 
will not differ notably in magnitude from those of other 



268 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



middle- and low-latitude stations. The results for Pet- 
samo, on the other hand, are probably representative, in 
rough order of magnitude, of other stations within a belt 
of latitude about 10° wide, centered near, or slightly in- 
side, the average auroral zone. 

The data of 1932-33 do not include a case of a great 
magnetic storm. The storms of the Polar Year were of 
only moderate intensity, such as those of October 14 and 
December 15, 1932, and May 1 and August 4, 1933. At 
times of magnetic storm, the auroral zones expand equa- 
torwards to different distances at different times, and to 
a degree depending somewhat on the intensity of storm. 
Rates of change at times of great magnetic storm as large 
as about ten gammas per second in H and Z in middle 
latitudes and in H near the equator have been noted. 

Figures 195 and 196 show, respectively, the monthly 
variations in frequency of fluctuations of various rates 
of change and durations at Petsamo and Copenhagen. At 
both stations there is considerable evidence of a seasonal 
variation in frequency. The observed frequencies are 
greatest near the equinoxes and least at the solstices. 

The correspondence between the number of fluctua- 
tions per day and sunspot number is not close, but it is 
much greater for large sunspot numbers and large rates 
of change than for small sunspot numbers and small 
rates of change. There is an averaged and not a detailed 
correspondence between the frequency of small fluctua- 
tions and sunspot number. 

15. Latitude distribution of fluctuations. - -Figure 197 
shows evidence of a marked variation with latitude in the 
frequencies of small fluctuations with durations 10 to 500 
seconds in H, D, and Z and amplitudes greater than five 
gammas. It appears that in all latitudes fluctuations of 
this type occur most frequently for durations of about 50 
seconds. Very few fluctuations in Z appear with ampli- 
tudes greater than five gammas, even though two days of 
storm, March 24 and May 1, 1933, were included. 

Figure 198 shows the corresponding magnitudes per 
day of totaled magnetic impulses (1/2 ZAf At, where Af 
is the amplitude of the fluctuation and At the duration in 
seconds) for the same data as were used in deriving Fig- 
ure 197 for days having various magnetic character -fig- 
ures C, In general, marked increase in totaled impulses 
accompanies the increase in C, although it is noted that 
the totaled impulses on March 24 (C = 1.5) is consider- 
ably greater than on May 1 (C = 1.9). These results are 
shown in a somewhat different way in Figure 199 where 
the corresponding total numbers of fluctuations per day 
are given for various latitudes. 

The variation with local geomagnetic time in the num- 
bers of fluctuations is shown in Figure 200. At times 
of storm, there appears little variation in the bihourly 
frequencies. On less disturbed days in polar regions, 
the fluctuations are most numerous in the morning and 
evening near times when the maximum departures in the 
average disturbance daily variation appear. At Huancayo 
special conditions prevail and fluctuations are more 
numerous near noon. This tendency is possibly in evi- 
dence at other low- and middle-latitude stations also. 

Figure 201 shows that positive and negative depar- 
tures in each magnetic component appear with about equal 
frequency at all hours of day. The differences shown are 
unlikely to be real but rather indicate a psychological 
preference for positive fluctuations on the part of the 
measurer. Figure 202 shows roughly the variation with 
latitude of totaled impulses averaged according to local 
geomagnetic time. 



16. Frequency distribution of fluctuations of dura- 
tion five minutes to ten hours. --The foregoing sections 
were concerned chiefly with fluctuations of durations 
from ten seconds to five minutes. It was noted that very 
large numbers of fluctuations appeared with durations of. 
about 50 seconds, if duration of the fluctuation be defined 
as the time elapsing from its beginning to its ending. In 
view of the possibility of maxima in frequency for some- 
what longer durations, a cursory examination of the fre- 
quency of fluctuations of greater than five -minute dura- 
tion was undertaken. For this purpose use was made of 
records for one month only, December, 1932, for the sta- 
tions Petsamo and Copenhagen. 

Tables 115 and 116 show the frequencies of fluctua- 
tions found in H at Petsamo and Copenhagen. It will be 
noted that the frequencies diminish rapidly with increas- 
ing amplitude at both stations. These results are given 
separately for positive fluctuations (defined as those 
yielding a departure in the direction of the increasing 
horizontal intensity) and negative fluctuations (defined as 
those yielding a departure in the direction of decreasing 
horizontal intensity). Although there may be a possibil- 
ity of some secondary maximum in frequency for dura- 
tions between five minutes and ten hours, it is seen that 
this maximum must at any rate be small. It may also be 
noted that negative fluctuations appear more frequently 
than positive fluctuations at Petsamo, whereas at Copen- 
hagen the situation is reversed. 

17. Geographical distribution of large short-period 
magnetic fluctuations . — A considered estimate is now 
presented, though based on scanty data, of the probability 
of occurrence of large amplitudes in short-period fluctu- 
ations, for different geographical positions. The class of 
fluctuations dealt with includes all those with durations of 
150 seconds or less as measured from beginning to end- 
ing of the fluctuation, whether a part of a larger and long- 
er fluctuation or otherwise. In all cases, it is understood 
that the fluctuation has an obvious initial departure and a 
complete subsequent recovery. 

The process used in arriving at a distribution of am- 
plitudes is rather unsatisfactory. In the first place, the 
frequency of fluctuations per three -month interval cannot 
be statistically assessed with much pretense at accuracy 
without, say, 20 to 30 years of data. Such extensive data 
on short-period fluctuations have never been obtained. In 
high latitudes, the longest series of short-period data 
measured has been obtained for about one year, giving a 
statistical sample for four three-month intervals. In low 
and middle latitudes, the time -scales used ordinarily 
have not had sufficient resolution for any except the long- 
er periods of fluctuation of one to two minutes. More- 
over, in earlier years larger magnets were used in var- 
iometers so that the fidelity of response to fluctuations 
of duration less than one -half minute was probably frequent- 
ly at fault. However, to obtain a rough approximation to the 
variation in amplitude with latitude, the 10, 20, and 30 • 
largest fluctuations observed o* six days in March to 
July, 1933, were tabulated for several stations. In all 
components, the largest amplitudes appear near the au- 
roral zone in the three sets of fluctuations as shown in 
the table at the top of the next page. 

It is now assumed that the latitude distribution above 
indicated applies also to the larger fluctuations — those 
so large that they appear on an average only in one three- 
month interval out of ten. (In a certain sense we may 
suppose this rate of appearance to be equivalent to the 
average incidence of one fluctuation per interval of 30 



FREQUENCIES OF GEOMAGNETIC FLUCTUATIONS 



269 



months or somewhat longer, say once every three years.) 
Hence, a fluctuation of the large amplitude sought is only 
infrequently found on the records of magnetic observa- 
tories. A rapid inspection of magnetograms for one year 



Observa- 
tory 


$ a 


Maximum amplitudes for 10, 20, 
and 30 fluctuations in 


H 


D 


Z 




10 


20 


30 


10 


20 


30 


10 


20 


30 



y yyyyyyyy 

Thule 88.0 20 18 14 17 14 12 14 12 11 

Godhavn 79.8 41 34 30 25 22 20 32 26 24 

Reykjavik 70.2 74 62 54 52 44 38 36 28 25 

Petsamo 64.9 56 51 48 44 36 31 77,_ 60 50 



RudeSkov 55.8 19 16 14 14 12 10 







Huancayo - 0.6 11 10 9 7^ 
Watheroo -41.8 6 9 8 8 5 b 



Geomagnetic latitude. D Less th an t en cases measured. 

showed that there were two or three fluctuations of dura- 
tion about two to three minutes with an amplitude in hori- 
zontal intensity (H) between 250y and 300y at Petsamo. 
Thus, the probability of such amplitudes in H near the 
auroral zone appears greater than 0.1 per three -month 
interval. If we suppose then that the amplitude is about 
600y at the auroral zone, for an average probability of 
0.1 per three-month interval, and we extrapolate from 
this and from corresponding amplitudes of fluctuations 
of probability 1.0, 0.5, and 0.25 per three-month interval, 
we arrive at a rough approximation such as that of Fig- 
ure 203. In a similar manner we obtain Figures 204 and 
205. 

As a rough and general check, the isomagnetic lines 
show a latitude distribution in amplitude somewhat simi- 
lar to the known latitude distribution of the disturbance 
daily variation. Among the cases observed over a long 
period of time, there will be included a few of the sudden 
commencements of occasional large magnetic storms. 

Near the equator there are two regions where the 
solar daily variation on quiet days is anomalously large 
and sometimes accompanied by sharp fluctuations near 
noon. Accordingly, the records for one year at Huancayo 
were used to arrive at a possible amplitude for the fluc- 
tuations. 

It may be remarked that our study of short-period 
fluctuations has revealed that fluctuations of notably large 
amplitude usually have the longer durations. On the other 
hand, the duration of fluctuations in H, D, and Z which 
appear most frequently in all latitudes is about 50 seconds. 

18. The nature of magnetic fluctuations and their pos- 
sible current systems. --In view of the importance of an 
understanding of the variation in frequency of fluctuation 
with geomagnetic latitude, a short study was made of the 
geographical distribution of the disturbance vectors of 
small fluctuations. Figures 206 to 209 show to scale the 
maximum disturbances of several separate fluctuations 
of about ten-minute duration. The measurements are 
rough due to incomplete data respecting exact time. The 
horizontal disturbance at the time of maximum departure 
of the fluctuation is shown by an arrow drawn from the 
station as origin and of a length proportional to the mag- 
nitude of the horizontal disturbance. The disturbance in 
vertical intensity (regarded as positive when in direction 



of the Earth's center) is indicated by a line drawn from 
the station as origin and positive when in the direction 
of the geomagnetic north pole. 

It appears from the figures that the larger part of 
disturbance is confined to the region near and within the 
auroral zone (shown by a dotted curve). The persistence 
of very small fluctuations throughout this extensive area 
is truly remarkable. In fact, each fluctuation appears to 
occur according to a systematic pattern, though distorted 
in the region just inside the auroral zone where its inci- 
dence and magnitude are less susceptible of accurate 
measurement because of additional small local irregu- 
larities in field. 

Outside the auroral zone, the fluctuations, though 
small in amplitude, are usually clearly evident. There 
is usually very small disturbance in vertical intensity. 

It will be noted that the fluctuations selected have field- 
characteristics somewhat similar inform. However, it 
cannot be concluded that these are typical in field-distri- 
bution of all other small fluctuations. In particular, it 
has been suggested by Chapman's students that in the 
case of highly regular sinusoidal pulsations, the disturb- 
ance felt at the Earth's surface more nearly resembles 
that due to a small oscillating magnet or dipole in the 
upper atmosphere or that of a wave-line dipole parallel 
to the Earth's surface. The field of fluctuations is fur- 
ther complicated by uncertainties as to the amount of the 
contribution due to induced earth currents produced by 
variations in the external inducing field. 

It is impossible in principle to infer uniquely from 
magnetic measurements at the Earth's surface alone the 
location and form of the electric current system respon- 
sible. The problem has not one but an infinity of solu- 
tions. A possible current system seems to resemble 
that of the diurnally varying part of the electric current 
system of geomagnetic disturbances as shown in the case 
of magnetic storms, the resemblance in low and middle 
latitudes being least clearly defined. It appears that the 
current system tends to remain more or less fixed rela- 
tive to the position of the Sun. This finding is in harmony 
with a dependence of fluctuations in number and intensity 
upon local time. 

The observed daily variations in frequency are in ac- 
cord with the supposition that the fluctuations are larger 
at times of day when the current intensity is greater over- 
head in the current systems responsible for the large sys- 
tematic variations of geomagnetism. The fluctuations 
may then be regarded as due to statistical fluctuations 
in the distribution and magnitude of the electrical con- 
ductivity in ionized regions of the atmosphere. Irregu- 
larities of patchy and transient form in the ionosphere 
are in fact known to occur from radio echoes, as shown 
by sporadic E-region reflections and others. It is more 
or less established that the currents responsible for the 
solar daily variation flow near the 100-km level of the 
atmosphere; since transient changes appear in ionization 
at this level, especially in higher latitudes, they must be 
accompanied by current-fluctuations. This conclusion is 
strengthened somewhat by the fact that the abnormally 
large solar daily variation at Huancayo is accompanied 
by abnormally large short-period fluctuations near noon. 

In the same way, the morning and evening maxima in 
magnitude of fluctuations of slightly longer period appear 
at times when the disturbance daily variation, most 
marked near the auroral zone, is greatest in amplitude 
[37]. It may be possible to account for a large number 
of the smaller irregular fluctuations on this basis. 



270 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



The trains of fluctuations appearing successively at 
times seem, on the other hand, to imply regular fluctuat- 
ing current on such occasions. As Terada suggests, these 
may be due to regional vertical oscillations of the atmos- 
phere; evidence of such oscillations may in fact be indi- 
cated by the oscillations in electron-density detected by 
Harang above Tromso. These had the same period as an 
accompanying sinusoidal magnetic fluctuation [55]. 

The fluctuations of about ten-minute duration shown 
in Figures 206 to 209 are of different type than those just 
mentioned in that they are world-wide rather than local 
in character. The electromotive forces driving the cur- 
rent originate possibly in auroral regions, and there is a 
return circuit of current symmetrical about the equator 
in low and middle latitudes. The simultaneous incidence 
of the small fluctuations in both the Northern and South- 
ern Hemispheres is remarkable. 

The observed rapid decay of field suggests that the 
electric currents responsible flow near or below the E- 
region of the ionosphere where the collisional frequency 
of ions and electrons is greater, so that rapid decay is 
possible. 

A suggestion was made several years ago by Johnson 
that it was possible that emanations emitted by the Sun 
would show certain qualities characteristic of thermionic 
emitters in general. According to the theory of magnetic 
disturbances of Chapman and Ferraro, neutral streams 
or beams of charged particles proceed from equatorial 
regions of the Sun. These streams, propelled from the 
rotating Sun, overtake the Earth as it moves along its 
orbit. If these streams comprise individual clouds of 
particles suitably distributed statistically, the preferred 
frequency of fluctuations for durations of the order of 50 
seconds might be explained on the basis of the size of 
cloud, its velocity and cross-section area. Because of 
energy considerations, the direct field of moving charges 
would be less likely to be responsible than would the in- 
direct effect of changed conductivity of impinging parti- 
cles in the atmosphere. In other words, a study of the 
spectrum of geomagnetic fluctuations may throw light on 
the statistical distribution of the numbers of component 
particles of the stream. 

Studies of magnetic fluctuations in conjunction with 
high-speed ionospheric recordings are of considerable 
interest. Those conducted by Japanese scientists in 1942 
showed numerous rapid changes in electron-density of 
the F2-region during disturbances. These findings were 
independently verified by Wells, Watts, and George [57]. 

19. Dependency of frequency and magnitude of small 
fluctuations of magnetic activity. --Using the data of Fig- 
ure 197 for Copenhagen, an examination was made of the 
dependence of frequency of fluctuations per day upon the 
magnetic character -figure C of the day. The correlation, 
carried out for the H -component only, was quite small 
and nearly negligible. The correlation-coefficient in- 
creased to +0.3 in the case of fluctuations with time-rate 
of change greater than 0.6y per second. It was concluded 
that the frequency of small fluctuations does not depend 
much on magnetic activity in the latitude of Copenhagen 
but that larger fluctuations appear with greater frequency 
when the magnetic activity is greater. 

20. Short-period magnetic fluctuations on land com- 
pared with those over or within ocean areas. - -Short- 
period geomagnetic fluctuations induce electric currents 
in the oceans which give a field additive to that of the in- 
ducing field. A colleague, Dr. Norman Davids, calculated 
the magnitude of the induction effects for the case of an 



electrically conducting ocean confined between two par- 
allel planes. The ocean conductivity was taken as 10-H 
CGS, ten thousand times that of surface rocks. 

The results indicate that the short-period geomag- 
netic fluctuations measured over the ocean will have an 
amplitude in horizontal intensity not in excess of twice 
that noted on land, and in the vertical component, an am- 
plitude less that that on land. The value of the horizon- 
tal component falls off rapidly with depth of ocean, when 
the linear cross-section of the inducing field is 100 
times or more that of the depth of ocean, and the period 
of this field is of the order one minute. Under these 
conditions, both the horizontal and vertical components 
are almost zero at a depth of 100 meters. 

The slower the period of the inducing field, the 
deeper do the induced currents penetrate. For short- 
period fluctuations of some minutes' duration, the in- 
duced currents flow mainly near the surface of the ocean. 
With.increasing depth, the shielding effect on the vertical 
component increases; in the case of horizontal intensity, 
there is no shielding but rather augmentation of field. 
The maximum difference between values observed on 
land and at the ocean's bottom is 100 per cent. 

A brief mathematical analysis showed that lightning 
occurring vertically above the ocean's surface can yield 
fields of several gauss in horizontal intensity enduring 
about 0.001 second, in a neighborhood within the ocean 
some tens of meters away from the point of discharge. 
Within the water, the field falls off rapidly with increas- 
ing horizontal distance and depth. 

Magnetograms for the Huancayo Magnetic Observa- 
tory, where the incidence of thunderstorms is high, do 
not reveal deflections in excess of 30 gammas per three - 
month interval due to lightning (see Figure 210); it is to 
be noted that the period of free oscillation of the magnet- 
system of the variometer is of the order of a few seconds. 
Because the area of influence is small and the discharges 
infrequent, the effects of lightning discharges are rarely 
recorded at observatories. 

21. Measurements of fluctuations of very short peri- 
od with instruments of improved response and increased 
time resolution. --As mentioned previously, few data are 
available respecting geomagnetic fluctuations of frequen- 
cies from 104 to about three cycles per second. It has 
already been noted that la Cour magnetographs use mag- 
net-systems which do not respond well to fluctuations of 
a few seconds' duration and less. However, the indica- 
tions from the latter have been that geomagnetic fluctua- 
tions of higher frequency exist, but little reliable infor- 
mation as to their true magnitude has been obtained. 

Accordingly, the Naval Ordnance Laboratory ar- 
ranged to provide photoelectric recording fluxmeters 
and search coils, with good response to fluctuations 
from about one to ten cycles per second. These are 
described in as yet unpublished reports of W. G. Mar- 
burger, S. Gilford, and E. A. Campbell of that labora- 
tory. The response at lower frequencies was intention- 
ally repressed, so that the record would show mainly 
those fluctuations of higher frequency. However, as 
shown in the preceding analysis, most short-period fluc- 
tuations of large amplitude endure for about 50 seconds, 
and these were recorded with fair response, but those 
of periods of some minutes were rather successfully re- 
pressed, except on rare occasions when they were large 
in amplitude and hence accompanied by large rates of 
change of field. The search coils used were so designed 
that scale values of a few gammas per millimeter were 



FREQUENCIES OF GEOMAGNETIC FLUCTUATIONS 



271 



achieved on the pen-and-ink record, with time resolution 
of about 0.2 seconds. 

Installations of equipment were made at College, 
Alaska, and Cheltenham, Maryland. 

22. Fluxmeter apparatus .--The fluxmeters used both 
at College and Cheltenham are described in General Elec- 
tric Instructions GEI-14903 [58]. 

The installation at Cheltenham, Maryland, has also 
been described by others [59], as well as the adjustment 
and calibration of the instruments [60]. 

The fluxmeter installations were designed to measure 
short-period magnetic changes in horizontal intensity (H) 
and vertical intensity (Z) at a sensitivity of about 3y. 
During August, 1942, the instruments were operated con- 
tinuously at a chart speed of six inches per minute — per- 
mitting time resolution to better than 0.2 second. 

The response characteristics of the fluxmeters used 
in obtaining the data here discussed will not be consider- 
ed in detail. For convenience in recording, it was neces- 
sary to maintain an appreciable restoring torque in these 
instruments. Their response approximated that of a true 
fluxmeter for short-period fluctuations. The results con- 
sequently are unsuitable for the study of geomagnetic fluc- 
tuations having durations of some mi: \utes. 

Figures 211 and 212 show the calculated responses of 
fluxmeters of the type here considered, for two different 
values of return-time-constants, namely, 80 seconds and 
51 seconds, as used at College, Alaska, during most of 
August, 1942. It is supposed that the impressed field is 
of the form c(l - cos mt), where c is a constant, m the 
frequency, and t the time in seconds; the calculations 
were made in the usual way, assuming that the response 
to a suddenly impressed unit magnetic field is initially 
perfect and that there then follows an exponential decay 
of the deflection in accordance with the return -time - 
constant. The return-time-constant is the time in sec- 
onds required to give an ordinate of trace equal to l/e 
(where e = 2.718) of its initial deflection. 

It appears that the results are in good agreement with 
expectation. The response for the initial half -period of 
the periodic impressed field is good for half -periods (du- 
rations) of one to about ten seconds. For longer dura- 
tions, the response deteriorates more rapidly as the pe- 
riod of the impressed field lengthens, when the return- 
time-constant is small. 

The calculations from theory agree well with those 
obtained experimentally. The response of the search- 
coil fpr horizontal intensity measurements with the flux- 
meter [61] shows that the quality of response is good for 
simple continuous fluctuations of field of durations one- 
half second to five seconds. It also appears that under 
certain conditions, for instance when isolated rather than 
• successive waves of geomagnetic fluctuations occur, the 
response may remain fair for fluctuations of duration of 
about a minute. This is shown by Figure 213, supplied by 
the Naval Ordnance Laboratory; the fidelity of response 
in amplitude apart from phase is indicated for various 
single-cycle fields, as measured at the Naval Ordnance 
Laboratory. A permalloy core in a coil was used for this 
experiment, however, so that the results indicated are in 
some respects approximate. For the particular fluxmeter 
tested, the response is rather goodfor a single-cycle field 
of two to ten seconds' duration for amplitudes as great as 
one milligauss (lOOy). For a single-cycle field of about 
100 seconds' duration, the recorded error in amplitude 
is about 40 per cent. Moreover, since a restoring torque 
is used yielding return-time -constants of the order of 30 



to 50 seconds, when several fluctuations of duration of 
about a minute or so appear in quick succession the rec- 
ord is very difficult to interpret without special detailed 
mathematical analyses. Without data of the type shown 
in Figure 213 for the actual fluxmeters in use at Chelten- 
ham or College, it was of course practically useless to 
make any attempt at an elaborate analysis which would 
require data on the response to a suddenly impressed 
unit field. Some data for fluctuations of duration longer 
than ten seconds were presented earlier for stations in 
different latitudes, obtained with instruments showing 
relatively high fidelity of response for durations greater 
than ten seconds. 

23. Fluxmeter installation at Cheltenham. Maryland. -- 
A of Figure 215 shows a view of the coil-installations at 
Cheltenham and of their underground locations as indi- 
cated by the disturbed soil in the foreground. The small 
building on the right in the foreground houses the fluxme- 
ters. B of Figure 215 shows the H- and Z -fluxmeters as 
installed at Cheltenham by Curtiss, Marburger, and oth- 
ers of the Naval Ordnance Laboratory. Each unit con- 
sists essentially of a large search-coil (about 18 feet in 
diameter with 1010 turns in five sections) of low resist- 
ance, connected directly to the fluxmeter element of a 
General Electric photoelectric recording fluxmeter. The 
coil for the H-fluxmeter was placed with its axis approxi- 
mately along the magnetic meridian. For the Z -fluxmeter 
the search-coil was placed with its axis vertical. 

Each coil consisted of five turns of 101 -pair lead- 
covered telephone cable, with each turn separately 
spliced so that all conductors were in series. Each loop 
of the cable then consisted of 202 turns, five sections hav- 
ing a total of 1010 turns per coil. 

In the initial exploratory installation, the fluxmeters 
at Cheltenham were operated to give a record at six inch- 
es per hour. A control (shown at the left of Figure 215) 
was provided for increasing the rate of travel of record- 
ing paper to six inches per minute at times of more 
marked magnetic disturbance. Later records were ob- 
tained using a rate of 24 inches per hour. The installa- 
tion at Cheltenham was maintained by the Naval Ordnance 
Laboratory, in co-operation with the United States Coast 
and Geodetic Survey. 

From the initial calibrations in June, 1942 [60], the 
sensitivities found were about 3.6y/mm for H and 3.9y/ 
mm for Z. The sensitivities of the H- and Z -coils were 
1881.5 and 1853.0 maxwell-turns per gamma, respective- 
ly, and the fluxmeter sensitivities were 13.1 and 13.8kilo- 
maxwell-turns, respectively. The return-time -constants 
were 58 seconds and 52 seconds, respectively, for posi- 
tive and negative deflections in H, and 35 seconds and 
32 seconds for corresponding deflections in Z. 

Several changes of instruments were made during the 
work, and there was some interruption of record during 
the testing of other types of equipment. A Z -fluxmeter 
installed March 13, 1943, had a scale value of 3.9y/mm 
with return-time-constants of 71 seconds and 45 seconds 
for deflections to the left and to the right, respectively. 
On April 8, 1943, the Naval Ordnance Laboratory advised 
that the H-fluxmeter needed replacement. The new flux- 
meter then installed had a sensitivity of 4.1y/mm with 
return-time-constants of 33 seconds and 20 seconds. 

24. Fluxmeter installation at College. Alaska. --At 
College, an installation similar to that at Cheltenham was 
made by the Department of Terrestrial Magnetism of the 
Carnegie Institution of Washington in accordance with 
specifications and instructions furnished by the Naval 



272 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



Ordnance Laboratory. During August, 1942, „ .uxme- 
ters at College were operated to yield records at six 
inches per minute, and later at 24 inches per hour. 

Figure 214 gives an aerial view of the College site 
taken in July, 1941. The location selected for the flux- 
meter coils is indicated. Details of construction of the 
H- and Z -coils are included in Figure 216, and the gen- 
eral plan of installation in Figure 217. As at Cheltenham, 
rigid underground construction eliminated spurious ef- 
fects due to mechanical vibration such as might be pro- 
duced by wind if the coils were placed aboveground. 

The average diameters of the H- and Z -coils were 
15 feet 2 inches and 15 feet 3 inches, respectively, with 
corresponding areas of 16.78 and 16.97 square meters, 
with 1010 turns in five sections as at Cheltenham. 

A schematic wiring diagram of the electrical circuits 
of the fluxmeter installation, showing means for the cali- 
bration and control of the instruments, is included in 
Figure 218. 

A standard mutual inductance with its secondary in 
series with the fluxmeter and search-coil was used to 
obtain the sensitivity of the meters. The breaking of a 
known primary current corresponded to a change of a 
given number of flux-turns, the meter deflection then 
giving directly the sensitivity in maxwell-turns per di- 
vision. 

Table 117 lists the sensitivities and return-time- 
constants of the fluxmeters. The sensitivity of the sys- 
tem is the ratio of the meter-sensitivity to the coil- 
sensitivity. 

Table 118 shows the variation in coil resistances as 
measured from time to time during the year. This vari- 
ation—due mainly to changes in ground temperature — is 
interesting in that the lowest resistance obtained corre- 
sponds to a temperature only slightly below freezing, 
this in spite of air temperatures falling at times to -50° C 

Table 119 gives sample determinations of fluxmeter 
sensitivities. 

General operation was for the most part without se- 
rious incident. In August, 1942, when continuous records 
at six inches per minute were taken, considerable dif- 
ficulty was experienced at first with the stopping of the 
driving mechanisms. This difficulty was largely over- 
come by the introduction of a variac voltage control. It 
was necessary to maintain a continuous watch of the ap- 
paratus during this month in order to ensure proper op- 
eration. At the later regular speed of trace of 24 inches 
per hour, little attention was required except for daily 
change of trace. 

25. Results of fluxmeter measurements. Cheltenham 
and College. --The chief finding from the fluxmeter meas- 
urements is that the short-period fluctuations of dura- 
tions of one to ten seconds are small in amplitude (usual- 
ly only a few gammas) both near the auroral zone and in 
middle latitudes. This is in good agreement with the re- 
sults of sections 14 to 16, where interpolated values on 
graphs such as Figure 195 suggested that few fluctua- 
tions of large amplitude and short duration would be 
found. As previously, for purposes of the foregoing con- 
clusions, a fluctuation is regarded as a departure of the 
geomagnetic field from normal, either representing a 
gradual diminution or an intensification to a minimum or 
maximum value, followed by a subsequent recovery to a 
normal value; the duration of a fluctuation is the time 
occupied in the complete process of appreciable change 
from and return to the normal value. A few of the short- 
period, low-amplitude fluctuations recorded by the flux- 



meters could be attributed to sharp variations in the 110- 
volt, 60-cycle power supply. 

So far as the results for Cheltenham are concerned, 
only one fluctuation in October, 1942, attained an ampli- 
tude in H of 30y. There was none of comparable size in 
either H or Z during August. The October fluctuation 
had a duration of 30 seconds measured at half its (total) 
maximum amplitude (30y); the initial rate of change at 
half -amplitude was 2y per second and the rate of recov- 
ery was similar. 

Since the times of beginning and ending of a fluctua- 
tion are as a rule rather indefinite, it is difficult to spec- 
ify exactly the duration. At the suggestion of the Naval 
Ordnance Laboratory, the duration was defined as the 
length in seconds on the time-scale measured at half- 
amplitude. 

Positive and negative fluctuations were taken to be in 
the directions of the respective increase or decrease in 
a field-component. The rates of change with time were 
measured at the position of the trace at half -amplitude, 
both for ascending and descending trace. 

Table 120 lists the frequencies of positive and nega- 
tive fluctuations of different amplitudes in H for various 
durations of fluctuations as defined above. Shown also in 
parentheses are the frequencies tentatively corrected 
using the results of Figures 211 and 212; these correc- 
tions are of course uncertain as it is very difficult to 
maintain consistent values of return-time-constant. The 
maximum frequencies are shown for durations of about 
60 seconds, in good agreement with results already dis- 
cussed; five cases were found with corrected amplitudes 
between 200y and 250y. 

Table 121 gives the corresponding results for Z. The 
number of fluctuations is less than one-tenth as great, the 
largest amplitude llOy, and the frequency distribution 
appears similar to that in H. 

Tables 122 and 123 list the same fluctuations in terms 
of initial and recovery rates of change in gammas per 
second for various durations in seconds. The largest ob- 
served initial rate of change in H was 12y/sec (correct- 
ed value 16y/sec) with duration 60 seconds; the largest 
recovery rate in H was lQy/sec (corrected value 12y/ 
sec) with duration 30 seconds. For Z the corresponding 
values were 6y/sec (corrected value 8y/sec) with dura- 
tion 50 seconds, and 2y/sec (corrected value 2y/sec) 
with duration 50 seconds. 

Table 124 lists the incidence of the fluctuations with 
time of day. They are most numerous in H near lOh 
and llh GMT (near or just after local midnight at Col- 
lege). 

The H -fluxmeter system at College was calibrated 
once each month and was operated at a sensitivity of 
about 8y per scale-division. Table 125 gives the four 
fluctuations of largest amplitude per month from Octo- 
ber 1, 1943, to January 31, 1944, uncorrected for return- 
time-constant of about 80 seconds. During the four- 
month period, the largest positive and negative fluctua- 
tions had amplitudes of +307y and -306y, respectively; 
the largest positive rate of change was +7.6y per sec- 
ond and the largest negative change -9.6y per second, 
for the class of fluctuations with complete duration less 
than 150 seconds. 

Figures 219 to 221 are examples of simultaneous 
records obtained at Cheltenham and College for quiet 
and disturbed days. It is noted that only rarely do the 
Cheltenham records depart appreciably from straight 
lines. 



FREQUENCIES OF GEOMAGNETIC FLUCTUATIONS 



273 



Additional sample records for College are given in 
Figure 222, showing how they may be characterized in 
one case by a series of regular damped oscillations, 
and in another case by high-frequency oscillations of 
fairly large amplitude — with periods of the order of 12 
seconds—superposed on long-period variations. 

Fluxmeters afford at any location a useful visual 
gage of current magnetic conditions. Disturbance ratings 
can in fact be assigned on an appropriate scale which will 
compare almost exactly with similar ratings derivedfrom 
the usual magnetograms. It has been found- -particularly 
in subpolar regions — that all radio-communication dis- 
turbances may be assessed for degree of disturbance by 
examination of the records of a suitable magnetic re- 
corder so that where ease of operation and maintenance 
is a significant factor, a fluxmeter installation may to 
some extent supplant the more complex ionospheric ap- 
paratus. 

As supplementing the usual records available at an 
observatory, fluxmeters may be of use in that they per- 
mit the study of rapid magnetic changes associated with 
intense sporadic E-region ionization and auroral activity. 

26. Unusually large short-period geomagnetic fluc- 
tuations measured at Ivigtut. Greenland. --In the summer 
of 1942, a magnetograph was installed by K. Thiesen at 
Ivigtut, Greenland. It was operated intermittently during 
that summer while a magnetic survey was in progress. 
In May, 1943, S. O. Corp, manager of the Ivigtut Cryo- 
lite Mines, generously offered to operate the observatory 
continuously. Dr. Thiesen returned to Ivigtut for a short 
time in 1943 to put the magnetograph in operation. The 
opportunity was taken also to have Dr. Thiesen install 
specially made short-period measuring elements in an- 
other set of la Cour variometers already mounted. 

Of particular interest at Ivigtut were a number of 
fluctuations of very short duration but of large amplitude 
(see Figure 223); such fluctuations were not observed in 
the fluxmeter records for College nor on the records of 
the la Cour magnetograpFfs at other stations during the 



Polar Year, 1932-33. The most marked of the Ivigtut 
fluctuations were: A fluctuation of 60y in H of semi- 
duration five seconds; 65y in D of semiduration five 
seconds; and 50y in Z of semiduration ten seconds. 
The records were not appreciably affected by the opera- 
tions at the cryolite mines so that these changes indicate 
short-period fluctuations of considerable magnitude at 
points just inside the auroral zone. 

27. Background, very small short-period fluctuations, 
at Turtle Mound, Florida, with portable magnetograph. — 
A portable magnetograph, designed and constructed at the 
Department of Terrestrial Magnetism of the Carnegie 
Institution of Washington, with flat response from zero 
to about three cycles per second, was operated at Turtle 
Mound, Florida, from December 1 to 15, 1943. A view of 
the portable magnetograph is given in Figure 225. The 
detecting element is shown in Figure 226; it consists of a 
small Alnico magnet attached to a quartz fiber, one side 
being polished to give a mirror -surface. The same ele- 
ment, of double-suspension type, can be used in the meas- 
urement of either H, D, or Z, and three elements are 
used. Auxiliary magnets are used for temperature-com- 
pensation and to adjust scale values. The motions of the 
magnet-systems are recorded optically on 35-mm micro- 
film. One loading of film will serve for 24 hours at high- 
speed operation with a time-resolution of about 0.3 sec- 
ond, or for about 140 days at slow speed. At Turtle Mound 
the sensitivity was somewhat less than one gamma per 
millimeter, the deflection of light spots being photo- 
graphed as they appeared on a milk-glass in front of the 
elements. 

The possible presence in low and middle latitudes of 
small geomagnetic fluctuations of amplitude greater than 
0.2y and period one second or less had been conjectured. 
The results at Turtle Mound (see typical five-minute rec- 
ord in Figure 224) revealed no evidence of fluctuations 
greater than 0.2y and duration less than one second. The 
magnetograph and the results at Turtle Mound will be 
described in greater detail later in this volume. 



TABLES 104-125 

Table Page 

104. List of magnetic observatories 276 

105. List of selected magnetic observatories 276 

106. Probability that daily ranges of horizontal intensity (H), magnetic declination (D), and 

vertical intensity (Z) will exceed various magnitudes in different geomagnetic lati- 
tudes ($), 12 months, 1932-33 277 

107. Expectation of average number of days elapsing before daily ranges in horizontal inten- 

sity (H), magnetic declination (D), and vertical intensity (Z) will exceed various mag- 
nitudes in different geomagnetic latitudes ($), 12 months, 1932-33 278 

108. Observed cumulative frequencies, computed probabilities, expected frequencies per 

year, and expected number of days elapsing for various daily ranges at different 

stations 279 

109. Probability that weekly ranges of horizontal intensity (H), magnetic declination (D), and 

vertical intensity (Z) will exceed various magnitudes in different geomagnetic lati- 
tudes ($) 280 

110. Probability that weekly, 1-, 2-, 3-, 4-, and 6-monthly ranges in horizontal intensity (H), 

magnetic declination (D), and vertical intensity (Z) will exceed various magnitudes 

at Tromso, Sitka, Cheltenham, and Honolulu 281 

111. Expectation of average number of weeks elapsing before weekly ranges in horizontal 

intensity (H), magnetic declination (D), and vertical intensity (Z) will exceed various 
magnitudes in different geomagnetic latitudes ($) 283 

112. Expectation of average number of time-periods elapsing before weekly, 1-, 2-, 3-, 4-, 

and 6-monthly ranges in horizontal intensity (H), magnetic declination (D), and vertical 

intensity (Z) will exceed various magnitudes at Tromso, Sitka, Cheltenham, and 

Honolulu 284 

113. Total number of fluctuations of various rates of change and semidurations for H, D, and 

Z, Petsamo, September 1, 1932, to August 31, 1933 286 

114. Total number of fluctuations of various rates of change and semidurations for H, D, and 

Z, Copenhagen, September 1, 1932, to August 31, 1933 287 

115. Frequency distribution of fluctuations in horizontal intensity of various amplitudes and 

durations of five minutes or more, Petsamo, December, 1932 288 

116. Frequency distribution of number of fluctuations in horizontal intensity of various ampli- 

tudes and durations of five minutes or more, Copenhagen, December, 1932 289 

117. Sensitivities and return-time-constants of fluxmeters, College, Alaska . . 289 

118. Resistances in ohms of H- and Z-coils, fluxmeter installation, College, Alaska 290 

119. Determination with standard mutual inductor of sensitivities in H- and Z-fluxmeters, 

College, Alaska 290 

120. Frequency distribution of fluctuations in horizontal intensity of various amplitudes and 

durations measured at half -amplitude and also corresponding frequencies roughly cor- 
rected for response defects of fluxmeter, College, Alaska, August, 1942 291 

121. Frequency distribution of fluctuations in vertical intensity of various amplitudes and 

durations measured at half -amplitude and also corresponding frequencies roughly 

corrected for response defects of fluxmeter, College, Alaska, August, 1942 292 

122. Total number of fluctuations in horizontal intensity of various rates of change and dura- 

tions measured at half -amplitude and also corresponding frequencies corrected for 
response defects of fluxmeter, College, Alaska, August, 1942 293 

123. Total number of fluctuations in vertical intensity of various rates of change and dura- 

tions measured at half -amplitude and also corresponding frequencies corrected for 

response defects of fluxmeter, College, Alaska, August, 1942 294 

124. Number of fluctuations for each GMT hour, College, Alaska, August, 1942 295 

125. Summary of largest positive and negative fluctuations, durations less than 150 seconds, 

horizontal intensity, H-fluxmeter, College, Alaska, November 1, 1943, to January 31, 

1944 296 



275 



Table 104. List of magnetic observatories 



Station 



$ 



A 



¥ 



Thule 


+ 76.5 


291.0 


+ 88.0 


0.0 


+ 0.0 


-81.3 


Godhavn 


+ 69.2 


306.5 


+ 79.8 


32.5 


-17.5 


-57.9 


Scoresby Sund 


+ 70.5 


338.0 


+ 75,8 


81.8 


-36.2 


-34.6 


Sveagruvan 


+ 77.9 


16.8 


+ 73.9 


130.7 


-46.? 


- 4.9 


Jan Mayen 


+ 71.0 


351.5 


+ 73.4 


96.3 


-37.5 


-22.7 


Calm Bay 


+ 80.3 


52.8 


+ 71.5 


153.3 


-32.2 


+ 21.2 


Bear Island 


+ 74.5 


19.2 


+ 71.1 


124.5 


-37.9 


- 1.9 


Juliannehaab 


+ 60.7 


314.0 


+ 70.8 


35.6 


-13.8 


-43.4 


Reykjavik 


+ 64.1 


338.2 


+ 70.2 


70.8 


-25.6 


-30.8 


Fort Rae 


+ 62.8 


243.9 


+ 69.0 


290.9 


+ 24.1 


+ 37.5 


Point Barrow 


+ 71.3 


203.3 


+ 68.6 


241.2 


+ 33.0 


+ 28.7 


Lycksele 


+ 64.6 


18.7 


+ 67.1 


116.4 


-30.8 


- 1.9 


Tromso 


+ 69.7 


18.9 


+ 67.1 


116.7 


-30.8 


- 3.7 


Petsamo 


+ 69.5 


31.2 


+ 64.9 


125.8 


-27.6 


+ 5.8 


Matotchkin Shar 


+ 73.3 


56.4 


+ 64.8 


146.5 


-22.4 


+ 21.7 


College 


+ 64.9 


212.2 


+ 64.5 


255.4 


+ 27.0 


+ 30.5 


Sodankyla 


+ 67.4 


26.6 


+ 63.8 


120.0 


-26.7 


+ 3.0 


Dickson 


+ 73.5 


80.4 


+ 63.0 


161.5 


-12.8 


+ 28.5 


Kandalakscha 


+ 67.1 


32.4 


+ 62.5 


124.2 


-25.0 


+ 1.8 


Lerwick 


+ 60.1 


358.8 


+ 62:5 


88.6 


-23.6 


-13.6 


Dombaas 


+ 62.1 


9.1 


+ 62.3 


100.0 


-23.6 


- 8.5 


Meanook 


+ 54.6 


246.7 


+ 61.8 


301.0 


+ 17.2 


+ 26.4 


Kajaani 


+ 64.2 


27.8 


+ 60.7 


118.0 


-23.9 


+ 3.1 


Sitka 


+ 57.0 


224.7 


+ 60.0 


275.4 


+ 21.4 


+ 30.2 


Eskdalemuir 


+ 55.3 


356.8 


+ 58.5 


82.9 


-20.4 


-14.3 


Lovo 


+ 59.4 


17.8 


+ 58.1 


105.8 


-22.1 


- 2.6 


Sloutsk 


+ 59.7 


30.5 


+ 56.0 


117.0 


-20.6 


+ 4.4 


Copenhagen (Rude Skov) 


+ 55.8 


12.4 


+ 55.8 


98.5 


-20.6 


- 5.6 


Agincourt 


+ 43.8 


280.7 


+ 55.0 


347.0 


+ 3.6 


- 7.6 


Abinger 


+ 51.2 


359.6 


+ 54.0 


83.3 


-18.4 


-11.9 


Val Joyeux 


+ 48.8 


2.0 


+ 51.3 


84.5 


-17.5 


-10.5 


San Miguel 


+ 37.8 


334.4 


+ 45.6 


50.9 


-11.3 


-18.2 


Ebro 


+ 40.8 


0.5 


+ 43.9 


79.7 


-15.0 


- 9.9 


Fernando Poo 


+ 3.4 


8.7 


+ 5.7 


78.6 


-11.3 


- 1.4 


Huancayo 


-12.0 


284.7 


- 0.6 


353.8 


+ 1.3 


+ 7.4 


Mogadiscio 


+ 2.0 


45.4 


- 2.7 


114.3 


-10.5 


- .9 


Elisabethville 


-11.7 


27.5 


-12.7 


94.0 


-11.7 


- 9.5 


Apia 


-13.8 


188.2 


-16.0 


260.2 


+ 11.7 


+ 10.7 


Cape Town 


-33.9 


18.5 


-32.7 


79.9 


-13.7 


-24.7 


Watheroo 


-30.3 


115.9 


-41.8 


185.6 


+ 1.3 


- 3.9 


Toolangi 


-37.5 


145.5 


-46.7 


220.8 


+ 9.5 


+ 8.5 


South Orkneys 


-60.8 


315.0 


-50.0 


18.0 


- 7.2 


+ 3.1 



Table 105. List of selected magnetic observatories 



Observatory (a) 


Geomagnetic* 


Angle 

y ** 


Geographic* 


Geomagnetic elements, 1932-33 


abbreviation (b) 


Lati- 
tude 


Longi- 
tude 
A 


Lati- 
tude 



Longi- 
tude 

X 


Decli- 
nation* 
D 


Horizontal 

intensity 

H 


Vertical 

intensity 

V 


(a) 


(b) 



Thule 


Th 


+ 88.0 


0.0 


0.0 


+ 76.5 


291.1 


-81.3 


Godhavn 


Go 


+ 79.8 


32.5 


-17.5 


+ 69.2 


306.5 


-57.9 


Bear Island 


BI 


+ 71.1 


124.5 


-37.9 


+ 74.5 


19.2 


- 1.9 


Juliannehaab 


lu 


+ 70.8 


35.6 


-13.8 


+ 60.7 


314.0 


-\?A 


Reykjavik 


Re 


+ 70.2 


70.8 


-25.6 


+ 64.1 


338.2 


-30.8 


Fort Rae 


FR 


+ 69.0 


290.9 


+ 24.1 


+ 62.8 


243.9 


+ 37.5 


Tromso 


Tr 


+ 67.1 


116.7 


-30.8 


+ 69.7 


18.9 


- 3.7 


Petsamo 


Pe 


+ 64.9 


125.8 


-27.6 


+ 69.5 


31.2 


+ 5.8 


Sodankyla 


So 


+ 63.8 


120.0 


-26.7 


+ 67.4 


26.6 


+ 3.0 


Sitka 


Si 


+ 60.0 


275.4 


+ 21.4 


+ 57.0 


224.7 


+ 30.2 


Sloutzk 


SI 


+ 56.0 


117.0 


-20.6 


+ 59.7 


30.5 


+ 4.4 


Rude Skov 


RS 


+ 55.8 


98.5 


-20.6 


+ 55.8 


12.4 


- 5.6 


Cheltenham 


Ch 


+ 50.1 


350.5 


+ 2.4 


+ 38.7 


283.2 


- 7.1 


Tucson 


Tu 


+ 40.4 


312.2 


+ 10.1 


+ 32.2 


249.2 


+ 13.9 


Honolulu 


Ho 


+ 21.1 


266.5 


+ 12.3 


+ 21.3 


201.9 


+ 10.1 


Bombay 


Bo 


+ 9.5 


143.6 


- 7.2 


+ 18.9 


72.8 


- 0.2 


Huancayo 


Hu 


- 0.6 


353.8 


+ 1.3 


-12.0 


284.7 


+ 7.4 


Pilar 


Pi 


-20.2 


4.6 


- 1.1 


-31.7 


296.1 


+ 6.1 


Watheroo 


Wa 


-41.8 


185.6 


+ 1.3 


-30.3 


115.9 


- 3.9 


South Orkneys 


SO 


-50.0 


18.0 


- 7.2 


-60.8 


315.0 


+ 3.1 



cgs 
.046 
.082 
.095 
.116 
.127 
.077 
.115 
.113 
.121 
.154 
.154 
.168 
.185 
.263 
.285 
.374 
.296 
.246 
.247 
.239 



cgs 
+ .558 
+ .554 
+ .516 
+ .529 
+ .500 
+ .600 
+ .502 
+ .508 
+ .493 
+ .551 
+ .473 
+ .448 
+ .542 
+ .450 
+ .234 
+ .178 
+ .010 
-.119 
-.513 
(-33) 



♦North latitudes considered positive, south latitudes negative; all longitudes are east; east declination positive 
west declination negative, horizontal intensity positive, vertical intensity positive in north and negative in south 
geomagnetic latitude. 

**•>£•= angular difference in direction at observatory between geographic and geomagnetic meridians, positive 
when measured from north around by east. 

276 



Table 106. Probability that daily ranges of horizontal intensity (H), magnetic declination (D), 

and vertical intensity (Z) will exceed various magnitudes in different 

geomagnetic latitudes ($), 12 months, 1932-33 













Probability that daily ranges will exceed 


magnitude 


in y 


of 




Ele- 


Observatory 


$* 


































































ment 









50 


100 


150 


200 


300 


400 


500 


600 


700 


800 


900 1000 1100 1200 1300 


H Thule , 


+ 88.0 


1.000 


.943 


.730 


.490 


.298 


.098 


.035 


.012 


.003 














Godhavn 


+ 79.8 


1.000 


.990 


.935 


.775 


.578 


.239 


.174 


.100 


.056 


.036 


.024 


.013 


.006 


.001 




Bear Island 


+ 71.1 


1.000 


.990 


.962 


.909 


.840 


.671 


.498 


.341 


.221 


.137 


.086 


.056 


.035 


.020 


.009 .002 


Juliannehaab 


+ 70.8 


1.000 


.990 


.971 


.926 


.862 


.699 


.529 


.373 


.256 


.174 


.120 


.085 


.058 


.038 


.021 


Fort Rae 


+ 69.0 


1.000 


.990 


.971 


.926 


.870 


.719 


.565 


.426 


.310 


.226 


.168 


.126 


.095 


.074 


.058 


Tromso 


+ 67.1 


1.000 


.943 


.855 


.746 


.641 


.478 


.'365 


.278 


.211 


.159 


.118 


.087 


.062 


.043 


.029 


Petsamo 


+ 64.9 


1.000 


.909 


.735 


.633 


.549 


.427 


.331 


.252 


.189 


.139 


098 


.067 


.044 


.027 


.015 


Sodankyla 


+ 63.8 


1.000 


.862 


.592 


.478 


.402 


.299 


.231 


.181 


.144 


.115 


.090 


.070 


.053 


.037 


.025 


Sitka 


+ 60.0 


1.000 


.654 


.309 


.205 


.152 


.098 


.063 


.037 


.016 


.003 












Rude Skov 


+ 55.8 


1.000 


.602 


.123 


.026 


.006 






















Cheltenham 


+ 50.1 


1.000 


.463 


.060 


.012 


.003 






















Tucson 


+ 40.4 


1.000 


.372 


.030 


.005 
























Honolulu 


+ 21.1 


1.000 


.186 


.022 


.005 
























Huancayo 


- 0.6 


1.000 


.980 


.685 


.212 


.045 






















Pilar 


-20.2 


1.000 


.375 


.047 


.008 


.000 






















Watheroo 


-41.8 


1.000 


.272 


.013 


























South Orkneys 


-50.0 


1.000 


.348 


.028 


.005 
























D Thule 


+ 88.0 


1.000 


.901 


.654 


.389 


.208 


.043 


.007 


.002 
















Godhavn 


+ 79.8 


1.000 


.980 


.870 


.667 


.412 


.204 


.113 


.069 


.044 


.027 


.015 


.007 


.002 






Bear Island 


+ 71.1 


1.000 


.971 


.885 


.741 


.585 


.353 


.198 


.096 


.037 


.012 


.003 










Juliannehaab 


+ 70.8 


1.000 


.962 


.826 


.690 


.568 


.385 


.251 


.158 


.096 


.057 


.030 


.012 


.003 






Fort Rae 


+ 69.0 


1.000 


.971 


.847 


.714 


.599 


.413 


.275 


.174 


.103 


.055 


.027 


.012 


.003 






Tromso 


+ 67.1 


1.000 


.885 


.602 


.467 


.362 


.217 


.132 


.086 


.055 


.031 


.014 


.003 








Petsamo 


+ 64.9 


1.000 


.826 


.538 


.407 


.310 


.178 


.099 


.052 


.023 


.006 












Sodankyla 


+ 63.8 


1.000 


.794 


.408 


.232 


.153 


.087 


.051 


.027 


.009 


.001 












Sitka 


+ 60.0 


1.000 


.855 


.418 


.222 


.128 


.056 


.031 


.015 


.004 














Rude Skov 


+ 55.8 


1.000 


.725 


.176 


.061 


.022 






















Cheltenham 


+ 50.1 


1.000 


.746 


.173 


.043 


.012 






















Tucson 


+ 40.4 


1.000 


.680 


.041 


.005 
























Honolulu 


+ 21.1 


1.000 


.403 


.008 


























Huancayo 


- 0.6 


1.000 


.176 


.008 


























Pilar 


-20.2 


1.000 


.380 


.010 


























Watheroo 


-41.8 


1.000 


.595 


.056 


.016 


.007 






















South Orkneys 


-50.0 


1.000 


.488 


.064 


.013 


.005 






















Z Thule 


+ 88.0 


1.000 


.709 


.373 


.179 


.075 


.013 


.001 


















Godhavn 


+ 79.8 


1.000 


.990 


.962 


.877 


.756 


.505 


.299 


.156 


.080 


.041 


.020 


.009 


.003 






Bear Island 


+ 71.1 


1.000 


.990 


.935 


.855 


.756 


.599 


.375 


.244 


.164 


.113 


.078 


.049 


.028 


.012 


.003 


Juliannehaab 


+ 70.8 


1.000 


.990 


.971 


.917 


.840 


.629 


.424 


.287 


.203 


.150 


.114 


.088 


.068 


.052 


.039 


Fort Rae 


+ 69.0 


1.000 


.990 


.943 


.862 


.775 


.588 


.429 


.304 


.209 


.139 


.089 


.055 


.033 


.016 


.005 


Tromso 


+ 67.1 


1.000 


.917 


.741 


.565 


.446 


.306 


.205 


.139 


.091 


.058 


.035 


.020 


.009 


.004 


.001 


Petsamo 


+ 64.9 


1.000 


.917 


.769 


.617 


.490 


.324 


.224 


.155 


.108 


.075 


.050 


.034 


.022 


.014 


.008 


Sodankyla 


+ 63.8 


1.000 


.847 


.645 


.508 


.405 


.255 


.148 


.081 


.044 


.026 


.016 


.009 


.005 


.003 


.001 


Sitka 


+ 60.0 


1.000 


.637 


.424 


.284 


.193 


.104 


.063 


.044 


.028 


.016 


.008 


.002 








Rude Skov 


+ 55.8 


1.000 


.364 


.126 


.059 


.039 


.025 


.011 


.003 
















Cheltenham 


+ 50.1 


1.000 


.137 


.024 


.007 
























Tucson 


+ 40.4 


1.000 


.053 


.009 


.004 
























Honolulu 


+ 21.1 


1.000 


.483 




























Huancayo 


- 0.6 


1.000 


.011 




























Pilar 


-20.2 


1.000 


.015 




























Watheroo 


-41.8 


1.000 


.408 


.125 


























South Orkneys 


-50.0 

































♦Geomagnetic latitude 



277 



Table 107. Expectation of average number of days elapsing before daily ranges in horizontal intensity (H), 

magnetic declination (D), and vertical intensity (Z) will exceed various magnitudes in 

different geomagnetic latitudes ($), 12 months, 1932-33 









E 


xpected average nu 


nber 


of days 


elapsing before 


daily 


range 


s 


Ele- 
ment 


Observatory 


* 












exceed magnitude 


in y of 















50 


100 


150 


200 


300 


400 


500 


600 


700 


800 


900 


1000 


1100 


1200 


1300 


H Thule 


+ 88.0 1 1 


1 


2 


3 


10 


28 


85 


380 








■ 




Godhavn 


+ 79.8 1 1 


1 




2 


4 


6 


10 


18 


28 


41 74 


185 


740 




Bear Island 


+ 71.1 1 1 


1 




1 


1 


2 


3 


5 


7 


12 18 


29 


50 


110 445 


Juliannehaab 


+ 70.8 1 1 


1 




1 


1 


2 


3 


4 


6 


8 12 


17 


27 


48 


Fort Rae 


+ 69.0 1 1 


1 




1 


1 


2 


2 


3 


4 


6 8 


10 


14 


17 


Tromso 


+ 67.1 1 1 


1 




2 


2 


3 


4 


5 


6 


8 12 


16 


23 


35 


Petsamo 


+ 64.9 1 1 


1 


2 


? 


2 


3 


4 


5 


7 


10 15 


23 


36 


65 


Sodankyla 


+ 63.8 1 1 


2 


2 


2 


3 


4 


6 


7 


9 


11 14 


19 


27 


40 


Sitka 


+ 60.0 1 2 


3 


5 


7 


10 


16 


27 


61 


325 










Rude Skov 


+ 55.8 1 2 


8 


39 


155 




















Cheltenham 


+ 50.1 1 2 


17 


80 


400 




















Tucson 


+ 40.4 1 3 


33 


200 






















Honolulu 


+ 21.1 1 5 


46 


215 






















Huancayo 


- 0.6 1 1 


1 


5 


22 






, 














Pilar 


-20.2 1 3 


21 


125 


2400 




















Watheroo 


-41.8 1 4 


75 
























South Orkneys 


-50.0 1 3 


36 


220 






















D Thule 


+ 88.0 1 1 


2 


3 


5 


23 


150 


630 














Godhavn 


+ 79.8 1 1 


1 


2 


2 


5 


9 


14 


23 


38 


65 140 


490 






Bear Island 


+ 71.1 1 1 


1 


1 


2 


3 


5 


10 


27 


86 


380 








Juliannehaab 


+ 70.8 1 1 


1 


1 


2 


3 


4 


6 


10 


17 


33 81 


300 






Fort Rae 


+ 69.0 1 1 


1 


1 


2 


2 


4 


6 


10 


18 


37 80 


320 






Tromso 


+ 67.1 1 1 


2 


2 


3 


5 


8 


12 


18 


32 


72 315 








Petsamo 


+ 64.9 1 1 


2 


2 


3 


6 


10 


19 


43 


160 










Sodankyla 


+ 63.8 1 1 


2 


4 


7 


12 


20 


37 


110 


1900 










Sitka 


+ 60.0 1 1 


2 


4 


8 


18 


32 


68 


240 












Rude Skov 


+ 55.8 1 1 


6 


16 


46 




















Cheltenham 


+ 50.1 1 1 


6 


24 


82 




















Tucson 


+ 40.4 1 1 


24 


180 






















Honolulu 


+ 21.1 1 3 


125 
























Huancayo 


- 0.6 1 6 


125 
























Pilar 


-20.2 1 3 


104 
























Watheroo 


-41.8 1 2 


18 


64 


140 




















South Orkneys 


-50.0 1 2 


16 


75 


190 




















Z Thule 


+ 88.0 1 1 


3 


6 


13 


80 


720 
















Godhavn 


+ 79.8 1 1 




1 


1 


2 


3 


6 


12 


25 


51 110 


380 






Bear Island 


+ 71.1 1 1 




1 


1 


2 


3 


4 


6 


9 


13 20 


36 


83 


330 


Juliannehaab 


+ 70.8 1 1 




1 


1 


2 


2 


3 


5 


7 


9 11 


15 


19 


25 


Fort Rae 


+ 69.0 1 1 




1 


1 


2 


2 


3 


5 


7 


11 18 


30 


61 


180 


Tromso 


+ 67.1 1 1 




2 


2 


3 


5 


7 


11 


17 


29 51 


106 


275 


1400 


Petsamo 


+ 64.9 1 1 




2 


2 


3 


4 


6 


9 


13 


20 30 


44 


71 


130 


Sodankyla 


+ 63.8 1 1 


2 


2 


2 


4 


7 


12 


23 


38 


64 110 


190 


380 


1500 


Sitka 


+ 60.0 1 2 


2 


4 


5 


10 


16 


23 


35 


61 


130 460 








Rude Skov 


+ 55.8 1 3 


8 


17 


26 


40 


90 


360 














Cheltenham 


+ 50.1 1 7 


42 


150 






















Tucson 


+ 40.4 1 19 


110 


230 






















Honolulu 


+ 21.1 1 21 


























Huancayo 


- 0.6 1 94 


























Pilar 


-20.2 1 69 


























Watheroo 


-41.8 1 2 


8 
























South Orknoys 


-50.0 



























''Geomagnetic latitude 



278 



Table 108. Observed cumulative frequencies (fc), and computed probabilities (P), expected frequencies 
per year (f e ), and expected number of days elapsing (E) for various daily ranges (R) 

at different stations 





25 

50 

75 

100 

125 

150 

175 

200 

300 

400 

500 

600 

700 

800 

900 

1000 



R 


fc 


P 


fe 


E 


fc 


P 


fe 


E 


fc 


P 


fe 


E 


fc 


P 


*e 


E 


y 


days 




days 


days 


days 




days 


days 


days 




days 


days 


days 




days 


days 








Sitka, 1905-26 










Sitka, 1932-33 








Hor 


zontal intensity (H) 


Vertical intensity (Z) 


Hori 


zontal intensity (H) 


Vertical inl 


.ensity (Z) 





7874 


1.0000 


365 


1 


7865 


1.0000 


365 


1 


362 


1.0000 


365 


1 


362 


1.0000 


365 


1 


100 


2106 


0.2675 


98 


4 


2516 


0.3199 


117 


3 


95 


0.2624 


96 


4 


139 


0.3840 


140 


3 


200 


973 


0.1236 


45 


8 


1163 


0.1479 


54 


7 


34 


0.0939 


34 


11 


61 


0.1685 


62 


6 


300 


596 


0.0757 


28 


14 


622 


0.0791 


29 


13 


15 


0.0414 


15 


24 


26 


0.0718 


26 


14 


400 


396 


0.0503 


18 


20 


356 


0.0453 


17 


22 


8 


0.0221 


8 


45 


12 


0.0331 


12 


30 


500 


281 


0.0357 


13 


28 


189 


0.0240 


9 


42 


3 


0.0083 


3 


120 


6 


0.0166 


6 


60 


600 


191 


0.0243 


9 


41 


105 


0.0134 


5 


75 


1 


0.0028 


1 


360 


4 


0.0110 


4 


91 


700 


148 


0.0188 


7 


53 


51 


0.0065 


2 


154 


1 


0.0028 


1 


360 


1 


0.0028 


1 


3R0 


800 


106 


0.0135 


5 


74 


23 


0.0029 


1 


345 





0.0000 







1 


0.0028 


1 


360 


900 


72 


0.0091 


3 


110 


10 


0.0013 





769 










1 


0.0028 


1 


360 


1000 


44 


0.0056 


2 


178 


8 


0.0010 





1000 










1 


0.0028 


1 


360 


1100 


30 


0.0038 


1 


263 


5 


0.0006 





1700 













0.0000 







1200 


22 


0.0028 


1 


357 


3 


0.0004 





2500 


















1300 


15 


0.0019 


1 


526 





0.0000 























1400 


5 


0.0006 





1700 





































Sloutzk, 1878 


-1939 










Bombay, 1882- 


1905 




Horizontal inte 


nsi 


ty (H) 




Declination 


(D) 


Vertical inte 


asity (Z) 


Horizontal intensity (H) 


20? 


















1072 


0.04737 


17 


21 










60? 


1029 


0.04547 


17 


22 


























60 










1062 


0.0469 


17 


21 


















70 


























346 


0.0395 


14 


25 


100 


963 


0.04255 


16 


24 


1022 


0.0416 


15 


22 


913 


0.04034 


15 


25 


294 


0.0336 


12 


30 


200 


355 


0.01568 


6 


64 


384 


0.0170 


6 


59 


435 


0.01922 


7 


52 


63 


0.0072 


3 


139 


300 


138 


0.00609 


2 


164 


116 


0.0051 


2 


195 


206 


0.00910 


3 


110 


19 


0.0022 


1 


454 


400 


72 


0.00318 


1 


314 


50 


0.0018 


1 


568 


98 


0.00433 


2 


231 


8 


0.0009 





1100 


500 


38 


0.00167 


1 


600 


27 


0.0012 





840 


53 


0.00234 


1 


427 


4 


0.0005 





2000 


600. 


22 


0.00097 





1030 


12 


0.0005 





2000 


27 


0.00119 





840 


3 


0.0003 





3300 


700 


13 


0.00057 





1750 


6 


0.0003 





3300 


12 


0.00053 





1890 


1 


0.0001 





10000 


800 


9 


0.00040 





2500 


4 


0.0002 





5000 


6 


0.00026 





3800 


1 


0.0001 





10000 


900 


7 


0.00031 





3200 


2 


0.0001 





10000 


3 


0.00013 





7700 





0.0000 







1000 


2 


0.00009 





11000 


1 


0.00004 





25000 


1 


0.00004 





25000 










1100 


2 


0.00009 





11000 





0.00000 







1 


0.00004 





25000 










1200 


2 


0.00009" 





11000 













0.00000 















1300 


1 


0.00004 





25000 


























1400 


1 


0.00004 





25000 


























3200 


1 


0.00004 





25000 



























Cheltenham, 1905-30 



Cheltenham, 1932-33 



Horizontal intensity (H) 
9485 1.0000 365 1 



836 0.0881 



32 



12 



77 
27 
12 
9 
6 
5 
2 
1 




0.0081 
0.0028 
0.0013 
0.0009 
0.0006 
0.0005 
0.0002 
0.0001 
0.0000 



3 123 

1 357 

769 

1100 

1700 

2000 

5000 

10000 




Vertical intensity (Z) 
9487 1.0000 365 1 



299 0.0315 11 



32 



81 

32 
16 
11 
6 
3 
1 




0.0085 
0.0034 
0.0017 
0.0012 
0.0006 
0.0003 
0.0001 
0.0000 



3 117 

1 294 

1 588 

833 

1700 

3300 

10000 




Horizontal intensity 

365 1.0000 365 

357 0.9781 357 

181 0.4959 181 

45 0.1233 45 

15 0.0411 15 

3 0.0082 3 

. 1 0.0027 1 

1 0.0027 1 

0.0006 



(H) 



Vertical intensity (Z) 



1 


365 


1.0000 


365 


1 


1 


143 


0.3918 


143 


3 


2 


36 


0.0986 


36 


10 


8 


7 


0.0192 


7 


52 


24 


3 


0.0082 


3 


120 


120 


1 


0.0027 


1 


370 


370 


1 


0.0027 


1 


370 


370 


1 


0.0027 


1 


370 







0.0000 








279 



Table 109. Probability that weekly ranges of horizontal intensity (H), magnetic declination (D), and vertical intensity (Z) 
will exceed various magnitudes in different geomagnetic latitudes ($ ) 

(Probabilities based on data for 12 months during Polar Year of 1932-33) 



Ele- 


Observa- 
tory and 








Probability that weekly ranges 


will exceed magnitude of y 


in 






ment 





50 


100 


150 


200 


300 


400 


500 


600 


700 


800 


900 


1000 


1100 


1200 


1300 


1400 


1500 


1600 


1700 


H Th +88.0 


1.000 1.000 


.980 


.901 


.787 


.481 


.115 


.038 






















Go +79.8 


1.000 1.000 1.000 1.000 


.980 


.826 


.578 


.424 


.308 


.154 


.135 


.115 


.077 












BI +71.1 


1.000 1.000 1.000 1.000 1.000 1.000 


.952 


.877 


.714 


.617 


.476 


.405 


.310 


.214 


.071 


.024 






Ju +70.8 


1.000 1.000 1.000 1.000 1.000 1.000 


.980 


.943 


.826 


.694 


.559 


.424 


.288 


.192 


.115 


.096 


.058 


.019 


FR +69.0 
Tr b +67.1 


1.000 1.000 1.000 1.000 1.000 1.000 1.000 


.962 


.901 


.826 


.633 


.442 


.403 


.250 


.192 


.096 


.058 




1.000 1.000 1.000 1.000 1.000 


.943 


.885 


.617 


.481 


.365 


.270 


.058 














Pe +64.9 


1.000 1.000 


.980 


.980 


.980 


.980 


.926 


.885 


.787 


.617 


.518 


.424 


.308 


.231 


.173 


.096 


.038 


.019 


So +63.8 


1.000 1.000 1.000 


.943 


.926 


.926 


.826 


.654 


.500 


.500 


.442 


.365 


.308 


.115 


.096 


.038 


.019 


.019 


Si +60.0 


1.000 1.000 


.787 


.654 


.481 


.308 


.173 


.077 


.058 


.038 


.038 


.019 


.019 


.019 


.019 


.019 


.019 


.019 


RS +55.8 


1.000 .980 


.500 


.135 


.038 


.019 


























Ch +50.1 


1.000 .943 


.403 


.038 


.019 




























Tu +40.4 


1.000 .885 


.250 


.019 


.019 




























Ho +21.1 


1.000 .769 


.154 


.019 






























Hu - 0.6 


1.000 1.000 


.980 


.730 


.308 


.019 


.019 






* 


















Pi -20.2 


1.000 .980 


.288 


.058 


.019 




























Wa -41.8 


1.000 .885 


.154 


.019 






























SO -50.0 


1.000 .926 


.211 
































D Th +88.0 


1.000 1.000 


.980 


.901 


.769 


.365 


.058 


.019 






















Go +79.8 


1.000 1.000 1.000 1.000 


.926 


.806 


.538 


.365 


.173 


.135 


.058 


.019 














BI +71.1 


1.000 1.000 1.000 1.000 1.000 


.909 


.645 


.422 


.156 


.067 


.022 
















Ju +70.8 


1.000 1.000 1.000 1.000 1.000 


.943 


.847 


.654 


.538 


.403 


.192 


.077 


.058 


.038 










FR +69.0 
Trb+67.1 


1.000 1.000 1.000 1.000 1.000 


.962 


.806 


.633 


.424 


.288 


.173 


.115 


.019 












1.000 1.000 


.901 


.654 


.442 


.115 


.019 
























Pe +64.9 


1.000 1.000 1.000 


.943 


.901 


.667 


.450 


.255 


.098 


.078 


















So +63.8 


1.000 1.000 


.962 


.769 


.518 


.385 


.192 


.135 


.077 


.038 


















Si +60.0 


1.000 1.000 


.943 


.709 


.518 


.231 


.058 


.019 






















RS +55.8 


1.000 1.000 


.694 


.308 


.173 




























Ch +50.1 


1.000 .980 


.617 


.154 


.115 




























Tu +40.4 


1.000 .943 


.308 
































Ho +21.1 


1.000 .752 


.019 
































Hu - 0.6 


1.000 .578 


































Pi -20.2 


1.000 .752 


.019 
































Wa -41.8 


1.000 .943 


.231 


.038 


.019 




























SO -50.0 


1.000 .980 


.365 


.019 


.019 




























Z Th +88.0 


1.000 .926 


.709 


.450 


.308 


.135 


.019 
























Go +79.8 


1.000 1.000 1.000 1.000 1.000 1.000 


.901 


.595 


.442 


.211 


.135 


.019 














BI +71.1 


1.000 1.000 1.000 1.000 1.000 1.000 


.952 


.820 


.645 


.422 


.222 


.156 


.111 


.044 


.022 








Ju +70.8 


1.000 1.000 1.000 1.000 1.000 1.000 


.980 


.826 


.654 


.559 


.481 


.327 


.211 


.173 


.135 


.077 


.038 


.019 .019 .019 


FR +69.0 
Tr b +67.1 


1.000 1.000 1.000 1.000 1.000 1.000 


.980 


.962 


.826 


.694 


.500 


.403 


.308 


.250 


.135 


.077 


.058 


.038 .038 .019 


1.000 1.000 1.000 


.962 


.787 


.538 


.308 


.173 


.058 




















Pe +64.9 


1.000 1.000 1.000 1.000 1.000 


.806 


.633 


.500 


.461 


.365 


.270 


.173 


.096 


.077 


.058 


.019 


.019 




So +63.8 


1.000 1.000 1.000 1.000 1.000 


.885 


.578 


.365 


.231 


.154 


.077 


.038 


.038 


.038 










Si +60.0 


1.000 .980 


.926 


.787 


.694 


.442 


.288 


.154 


.096 


.019 


.019 


.019 


.019 












RS +55.8 


1.000 .847 


.442 


.192 


.038 


.019 


.019 
























Ch +50.1 


1.000 .481 


.077 


.038 






























Tu +40.4 


1.000 .058 


































Ho +21.1 


1.000 .173 


































Hu - 0.6 


1.000 .154 


































Pi -20.2 


1.000 .019 


































Wa -41.8 


1.000 .885 


.115 






• 


























SO -50.0 


No available data 































Geomagnetic latitude; see Table 105 for abbreviations to designate observatories. ^R 
mean hourly values at extremes. 



anges determined from 



280 



Table 110. Probability that weekly, 1-, 2-, 3-, 4-, and 6-monthly ranges in horizontal intensity (H), magnetic declination (D), 
and vertical intensity (Z) will exceed various magnitudes at Tromso, Sitka, Cheltenham, and Honolulu 

(Probabilities based on 8 years of data from Tromso Observatory and 26 years of data at each from 
Sitka, Cheltenham, and Honolulu Observatories) 



Ele- 
ment 



Time- 
period 



Probability that time-period ranges will exceed magnitude in y of 



50 100 150 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 



Weekly 

Monthly 

2-monthly 

3 -monthly 

4-monthly 

6-monthly 

Weekly 

Monthly 

2-monthly 

3 -monthly 

4-monthly 

6-monthly 

Weekly 

Monthly 

2-monthly 

3 -monthly 

4-monthly 

6-monthly 



Weekly 

Monthly 

2-monthly 

3 -monthly 

4-monthly 

6-monthly 

Weekly 

Monthly 

2-monthly 

3-monthly 

4-monthly 

6-monthly 

Weekly 

Monthly 

2-monthly 

3-monthly 

4-monthly 

6-monthly 



TROMSO ($ = +67°.l), based on data for 8 years, 1930-37 



1.000 1.000 1.000 .983 .966 .898 .794 .637 .462 .310 .179.099.051 .017 
1.000 1.000 1.000 1.000 1.000 1.000 1.000 .990 .896 .771 .594 .437 .292 .083 
1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 .989 .979 .832.674.474.253 
1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 .926 .833 .633 .442 
1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 .990 .943 .709 .559 
1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 .990 .893 .735 

1.000 1.000 .868 .670 .489 .164 .046 .012 

1.000 1.000 1.000 1.000 .885 .635 .229 .073 .021 

1.000 1.000 1.000 1.000 1.000 .8 7 4 .442 .189 .053 

1.000 1.000 1.000 1.000 1.000 .980 .671 .319 .085 

1.000 1.000 1.000 1.000 1.000 1.000 .826 .420 .140 

1.000 1.000 1.000 1.000 1.000 1.000 .943 .617 .242 

1.000 1.000 .989 .882 .747 .523 .339 .168 .074 

1.000 1.000 1.000 1.000 1.000 .964 .845 .595 .333 

1.000 1.000 1.000 1.000 1.000 1.000 .976 .881 .607 

1.000 1.000 1.000 1.000 1.000 1.000 .990 .990 .746 

1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 .855 

1.000 1.000 1.000 1.000 1.000 1.000 1.000 1.000 .990 



.005 
.031 
.081 
.168 
.258 
.450 



.002 
.010 
.021 
.032 
.054 
.121 



.022 
.167 
.298 
.433 
.556 
.800 



.003 .003 
.036 .012 
.107 .024 
.157 .036 
.222 .049 
.304 .076 



.003 
.012 
.024 
.036 
.049 
.076 



SITKA ($ = + 60°.0), based on data for 26 years, 1905-30 

,000 .971 .741 .585 .490 .370 .294 .234 .175 .140 .108 .079 .056 .045 .030 .020 .005 
.000 1.000 .990 .943 .870 .781 .704 .613 .515 .437 .372 .308 .253 .176 .131 .093 .026 



.000 1.000 1.000 .990 .952 
.000 1.000 1.000 .990 .980 



.909 .870 .800 .709 .613 .532 .461 .389 .318 .251 .190 .058 
.971 .943 .893 .813 .725 .617 .552 .500 .417 .336 .258 .090 .003 



.000 1.000 1.000 1.000 .990 .990 .971 .926 .870 .787 .685 .613 .578 .493 .424 .333 .123 .006 
.000 1.000 1.000 1.000 1.000 1.000 1.000 .952 .926 .855 .781.714 .658 .565 .503 .441 .192 .016 



.000 .990 .855 .633 .439 .224 

.000 1.000 1.000 .980 .877 .613 

.000 1.000 1.000 1.000 .980 .800 

.000 1.000 1.000 1.000 .990 .885 

.000 1.000 1.000 1.000 1.000 .926 

.000 1.000 1.000 1.000 1.000 .952 

.000 .962 .826 .690 .585 .417 

.000 1.000 .990 .980 .935 .820 

.000 1.000 1.000 .990 .980 .935 

.000 1.000 1.000 1.000 .990 .990 

.000 1.000 1.000 1.000 1.000 .990 

.000 1.000 1.000 1.000 1.000 1.000 



.128 .079 .049 .032 .023 .015 .009 .006 .004 .003 .002 .001 

.413 .282 .215 .135 .090 .964 .032 .022 .016 .010 .006 .003 .003 

.585 .441 .330 .235 .172 .118 .067 .048 .029 .019 .013 .006 .006 

.685 .546 .413 .307 .235 .171 .103 .077 .048 .029 .019 .010 .010 

.758 .629 .472 .366 .294 .214 .133 .100 .071 .042 .026 .013 .013 

.820 .714 .562 .446 .382 .280 .176 .156 .120 .068 .039 .020 .020 

.303 .207 .123 .064 .029 .016 .007 .003 .002 

.685 .575 .388 .237 .128 .071 .026 .010 .006 

.847 .725 .578 .370 .244 .138 .058 .026 .019 

.909 .806 .676 .488 .319 .203 .097 .042 .029 

.943 .877 .752 .595 .405 .256 .139 .065 .045 .003 

.971 .917 .840 .741 .498 .355 .189 .085 .062 .020 .007 .003 



281 



Table 110. Probability that weekly, 1-, 2-, 3-, 4-, and 6-monthly ranges in horizontal intensity (H), magnetic declination (D) 
and vertical intensity (Z) will exceed various magnitudes at Tromso, Sitka, Cheltenham, and Honolulu --concluded 

(Probabilities based on 8 years of data from Tromso Observatory and 26 years of data at each from 
Sitka, Cheltenham, and Honolulu Observatories) 



Ele- 
ment 



Time- 
period 



Probability that time-period ranges will exceed magnitude in y of 



50 100 150 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 



Weekly 

Monthiy 

2-monthly 

3-monthly 

4-monthly 

6-monthly 

Weekly 

Monthiy 

2-monthly 

3-monthly 

4-monthly 

6-monthly 

Weekly- 
Monthly 
2-monthly 
3-monthly 
4-monthly 
6-monthly 



1.000 .962 
1.000 1.000 
1.000 1.000 
1.000 1.000 
1.000 1.000 



.442 
.885 
.935 
.962 
.980 



1.000 1.000 1.000 

1.000 .962 .544 
1.000 1.000 .926 
1.000 1.000 .990 
1.000 1.000 1.000 
1.000 1.000 1.000 
1.000 1.000 1.000 

1.000 .485 -.186 
1.000 .892 .562 
1.000 .971 .763 
1.000 .980 .862 
1.000 1.000 .926 
1.000 1.000 .990 



CHELTENHAM ($ = +50°.l), based on data for 26 years, 1905-30 

.151 .062 .018 .011 .007 .005 .004 .002 .001 

.538 .247 .074 .048 .032 .022 .019 .006 .006 .003 .003 .003 

.741 .446 .154 .093 .064 .045 .039 .013 .013 .006 .006 .006 

.826 .552 .223 .132 .094 .068 .058 .019 .019 .010 .010 .010 

.885 .709 .285 .181 .126 .094 .078 .026 .026 .013 .013 .013 

.935 .820 .382 .251 .186 .147 .117 .042 .039 .020 .020 .020 

.229 .096 .024 .009 .004 .004 .004 .002 .002 .002 .002 .002 .001 .001 .001 .001 

.637 .350 .102 .035 .016 .013 .013 .006 .006 .006 .006 .006 .006 .006 .003 .003 

.840 .599 .196 .077 .032 .026 .026 .013 .013 .013 .013 .013 .013 .013 .006 .006 

.935 .735 .291 .123 .055 .0?9 .039 .019.019 .019 .019 .019 .019 .019 .010 .010 

.952 .800 .333 .149 .074 .062 .062 .03° .036 .036 .026 .026 .026 .026 .013 .013 

.990 .870 .478 .231 .114 .078 .078 .049 .039 .039 .039 .039 .039 .039 .020 .020 

.096 .061 .026 .014 .009 .005 .003 .001 

.340 .247 .122 .067 .038 .022 .013 .003 

.559 .424 .238 .141 .090 .045 .029 .006 

.676 .541 .342 .210 .139 .065 .042 .016 .003 .003 .003 

.769 .633 .433 .275 .185 .084 .055 .026 .007 .007 .007 

.909 .752 .588 .417 .297 .127 .078 .036 .016 .016 .016 

HONOLULU ($ = +21°.l), based on data for 26 years, 1905-30 



Weekly 

Monthly 

2-monthly 

3-monthly 

4-monthly 

6-monthly 

Weekly 

Monthly 

2-monthly 

3-monthly 

4-monthly 

6-monthly 

Weekly 

Monthly 

2-monthly 

3-monthly 

4-monthly 

6-monthly 



1.000 .847 .291 
1.000 1.000 .741 
1.000 1.000 .901 
1.000 1.000 .952 
1.000 1.000 .980 
1.000 1.000 1.000 



1.000 .847 
1.000 .962 
1.000 .990 
1.000 .990 
1.000 1.000 
1.000 1.000 



1.000 
1.000 
1.000 
1.000 
1.000 
1.000 



.241 
.662 
.877 
.943 
.980 
.000 



.075 
.290 
.441 
.592 
.662 
.763 

.004 
.019 
.042 
.077 
.110 
.221 



085 .035 .007 .004 .004 .002 .001 

358 .151 .032 .016 .013 .006 .003 

.301 .074 .032 .026 .013 .009 

.417 .110 .048 .C39 .019 .010 

.508 .162 .065 .052 .026 .013 



.610 
.725 
.883 
.901 



.641 .253 .097 .078 .039 .019 



.005 .001 .001 

.029 .009 .009 

.055 .006 .006 

.087 .010 .010 

.119 .013 .013 

.181 .019 .019 

.002 .001 

.010 .003 

.019 .006 

.029 .010 

.039 .013 

.058 .019 



282 



Table 111. Expectation of average number of weeks elapsing before weekly ranges in horizontal intensity (H), magnetic 
declination (D), and vertical intensity (Z) will exceed various magnitudes in different geomagnetic latitudes (<$) 

(Expectations based on data for 12 months during Polar Year 1932-33) 



Ele- 


Observe - 




Expected average 


lumber of 


weeks elapsing 


before daily ran 


ges exceed magnitude in y of 


ment 


tory 


and$ a 





50 


100 


150 


200 


300 


400 


500 


600 


700 


800 


900 


1000 1100 1200 1300 1400 1500 1600 1700 


H 


Th 


+ 88.0 


1.0 


1.0 


1.0 


1.1 


1.3 


2.1 


8.7 


26.0 














Go 


+ 79.8 


1.0 


1.0 


1.0 


1.0 


1.0 


1.2 


1.7 


2.4 


3.2 


6.5 


7.4 


8.7 13.0 






BI 


+ 71.1 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.1 


1.4 


1.6 


2.1 


2.5 3.2 


4.7 14.0 42.0 




Ju 


+ 70.8 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.1 


1.2 


1.4 


1.8 


2.4 3.5 


5.2 8.7 10.4 17.3 52.0 




FR 


+ 69.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.1 


1.2 


1.6 


2.3 2.5 


4.0 5.2 10.4 17.3 52.0 




Trb 


+ 67.1 


1.0 


1.0 


1.0 


1.0 


1.0 


1.1 


1.1 


1.6 


2.1 


2.7 


3.7 


17.3 






Pe 


+ 64.9 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.1 


1.1 


1.3 


1.6 


1.9 


2.4 3.2 


4.3 5.8 10.4 26.0 52.0 




So 


+ 63.8 


1.0 


1.0 


1.0 


1.1 


1.1 


1.1 


1.2 


1.5 


2.0 


2.0 


2.3 


2.7 3.2 


8.7 10.4 26.0 52.0 52.0 




Si 


+ 60.0 


1.0 


1.0 


1.3 


1.5 


2.1 


3.2 


5.8 


13.0 


17.3 


26.0 


26.0 


52.0 52.0 


52.0 52.0 52.0 52.0 52.0 




RS 


+ 55.8 


1.0 


1.0 


2.0 


7.4 


26.0 


52.0 


















Ch 


+ 50.1 


1.0 


1.1 


2.5 


26.0 


52.0 




















Tu 


+ 40.4 


1.0 


1.1 


4.0 


52.0 


52.0 




















Ho 


+ 21.1 


1.0 


1.3 


6.5 


52.0 



































Hu - 0.6 1.0 1.0 1.0 1.4 3.2 52.0 52.0 

Pi -20.2 1.0 1.0 3.5 17.3 52.0 

Wa -41.8 1.0 1.1 6.5 52.0 

SO -50.0 1.0 1.1 4.7 



D Th 


+ 88.0 


1.0 


1.0 


1.0 


1.1 


1.3 


2.7 


17.3 


52.0 




















Go 


+ 79.8 


1.0 


1.0 


1.0 


1.0 


1.1 


1.2 


1.9 


2.7 


5.8 


7.4 


17.3 


52.0 












BI 


+ 71.1 


1.0 


1.0 


1.0 


1.0 


1.0 


1.1 


1.6 


2.4 


6.4 


15.0 


45.0 














Ju 


+ 70.8 


1.0 


1.0 


1.0 


1.0 


1.0 


1.1 


1.2 


1.5 


1.9 


2.5 


5.2 


13.0 


17.3 


26.0 








FR 


+ 69.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.2 


1.6 


2.4 


3.5 


5.8 


8.7 


52.0 










Trb 


+ 67.1 


1.0 


1.0 


1.1 


1.5 


2.3 


8.7 


52.0 






















Pe 


+ 64.9 


1.0 


1.0 


1.0 


1.1 


1.1 


1.5 


2.2 


3.9 


10.2 


12.8 
















So 


+ 63.8 


1.0 


1.0 


1.0 


1.3 


1.9 


2.6 


5.2 


7.4 


13.0 


26.0 
















Si 


+ 60.0 


1.0 


1.0 


1.1 


1.4 


1.9 


4.3 


17.3 


52.0 




















RS 


+ 55.8 


1.0 


1.0 


1.4 


3.2 


5.8 


























Ch 


+ 50.1 


1.0 


1.0 


1.6 


6.5 


8.7 


























Tu 


+ 40.4 


1.0 


1.1 


3.2 






























Ho 


+ 21.1 


1.0 


1.3 


52.0 






























Hu 


- 0.6 


1.0 


1.7 
































Pi 


-20.2 


1.0 


L3 


52.0 






























Wa 


-41.8 


1.0 


1.1 


4.3 


26.0 


52.0 


























SO 


-50.0 


1.0 


1.0 


2.7 


52.0 


52.0 


























Z Th 


+ 88.0 


1.0 


1.1 


1.4 


2.2 


3.2 


7.4 


52.0 






















Go 


+ 79.8 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.1 


1.7 


2.3 


4.7 


7.4 


52.0 












BI 


+ 71.1 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.2 


1.6 


2.4 


4.5 


6.4 


9.0 


22.5 


45.0 






Ju 


+ 70.8 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.2 


1.5 


1.8 


2.1 


3.1 


4.7 


5.8 


7.4 


13.0 


26.0 52.0 52.0 52.0 


FR 


+ 69.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.0 


1.2 


1.4 


2.0 


2.5 


3.2 


4.0 


7.4 


13.0 


17.3 26.0 26.0 52.0 


Trb 


+ 67.1 


1.0 


1.0 


1.0 


1.0 


1.3 


1.9 


3.2 


5.8 


17.3 


















Pe 


+ 64.9 


1.0 


1.0 


1.0 


1.0 


1.0 


1.2 


1.6 


2.0 


2.2 


2.7 


3.7 


5.8 


10.4 


13.0 


17.3 


52.0 


52.0 


So 


+ 63.8 


1.0 


1.0 


1.0 


1.0 


1.0 


1.1 


1.7 


2.7 


4.3 


6.5 


13.0 


26.0 


26.0 


26.0 








Si 


+ 60.0 


1.0 


1.0 


1.1 


1.3 


1.4 


2.3 


3.5 


6.5 


10.4 


52.0 


52.0 


52.0 


52.0 










RS 


+ 55.8 


1.0 


1.2 


2.3 


5.2 


26.0 


52.0 


52.0 






















Ch 


+ 50.1 


1.0 


2.1 


13.0 


26.0 
























. 




Tu 


+ 40.4 


1.0 


17.3 
































Ho 


+ 21.1 


1.0 


5.8 
































Hu 


- 0.6 


1.0 


6.5 






























. 


Pi 


-20.2 


1.0 


52.0 
































Wa 


-41.8 


1.0 


1.1 


8.7 






























SO 


-50.0 


No available data 



























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ct) 












o 






H 




>> 


CO 










in. 










C 






<u 








to 




a 






, 






cd 






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rr 
















u 








Ol 






> 


CM 










en. 






N 




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c 










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td) 




a) 


c 




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cd 




o 


^ 




E-i 










O 




CO 


0) 


C 






"S 


O 




tH 


£ 


CD 


o 


rt 




C 


■* 


in. 


u 




c 


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o 


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CM 


rt 






-2 








3 












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I— < 








o 
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rt 


£ 




O 


3 




H 


Z 






>> 


CO 










to 






c 






CD 


CD 










a 








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a 


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a 
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N 












u 

o 


CM 




K 








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i 


i 




s 


u O 




o> 
1 w 


3 B 

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CO CO O O CN i-h o o o o o i-h o o o o o o o © oooooooo 



C-COMnnNOnOO i— i © i-h o o o o o o o oooooooo 



in CO i-h CO i-h O O O O O O O i-h rH r-t O i-h o 



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CO CD i-h 00 i-h i-h CO i-h O O CM CM i-h O O O O O O O OOOOOOOO 



CM "H* CM l-H i-h O O O i-H O O ri O O i-h O O O 



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286 



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CT> 


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03 


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U 


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if, 


S-, 


3 


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U 


s 


n 


a; 








a 


IM 


Oi 


o 


CO 


VI 


„ 


c 


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CD 


nj 

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as 

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c 


u 


0) 


3 


a 


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t- 




a 




j-i 




6 




3 




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5 




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co -a 



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to t-i ■^•"^cnTi-T 



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OJ [- O (D CD N rt « 
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inCM .^COrHOOlinn^iHHHHi-l 

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CD CT> CO j^ 



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287 



Table 115. Frequency distribut 


ion of fluctuati 


3ns in 


he 


rizontal intensity of various 


amplitudes and durations 








of five minutes or 


more, 


Petsamo 


December, 1932 


















Number i 


Df fluctuations of amplitude in 


y from 










Duration 
































minutes 


0- 


11- 


21- 


31- 


41- 


51- 




61- 


71- 


81- 


91- 


101- 


151- 


> 


Total 




10 


20 


30 


40 


50 


60 




70 


80 


90 


100 


150 


200 


200 












Number 


of positive fluctuations 












5 - 7.5 


20 


16 


3 


4 


3 


3 




1 




















50 


7.5- 12.5 


14 


14 


7 


5 


3 


3 




1 


1 


2 


2 


4 








56 


12.5- 17.5 


6 


7 


7 


4 


2 


2 




2 




















30 


17.5- 22.5 


2 


6 





3 


1 


2 
















2 





1 


17 


22.5- 27.5 


1 


1 


5 


1 


3 







1 


2 








2 








16 


27.5- 32.5 


1 


3 


2 


1 


1 


1 




1 








1 











11 


32.5- 37.5 


1 


2 





1 



















1 











5 


37.5- 42.5 








1 





1 


1 













1 





1 





5 


42.5- 47.5 


1 





1 


3 






















2 








7 


47.5- 52.5 





1 


2 





1 






















1 





5 


52.5- 62.5 





1 








1 







1 








1 





1 





5 


62.5- 72.5 




























1 














1 


72.5- 82.5 














1 






















1 


1 


3 


82.5- 92.5 

















1 




, 




















1 


92.5-102.5 














1 



















1 








2 


102.5-122.5 

























1 














1 


2 


122.5-142.5 































1 











1 


142.5-162.5 








































1 


1 


162.5-182.5 








1 

























1 








. 2 


182.5-202.5 


































1 


1 


2 


4 


>202.5 














































Total 
































positive 


46 


51 


28 


23 


18 


13 




7 


4 


3 


7 


13 


5 


6 


224 



Number of negative fluctuations 



5 - 


7.5 


139 


81 


30 


16 


5 


7 


5 


1 


11 


1 


4 


2 


1 


293 


7.5- 


12.5 


52 


58 


25 


8 


7 


7 


4 


4 





4 


6 


3 


2 


180 


12.5- 


17.5 


25 


39 


11 


8 


5 


5 


2 


2 


3 


1 


12 


7 


6 


126 


17.5- 


22.5 


13 


19 


12 


9 


4 


2 


1 








2 


3 





1 


66 


22.5- 


27.5 


2 


10 


5 


5 


1 


2 


1 


1 





1 


2 


1 


2 


34 


27.5- 


32.5 


4 


6 


5 








1 





2 





1 


3 


1 





23 


32.5- 


37.5 





2 

















1 





1 





2 





6 


37.5- 


42.5 


1 





3 


2 





1 











1 





1 


1 


10 


42.5- 


47.5 





3 


2 


1 











1 














1 


8 


47.5- 


52.5 


3 





1 





3 














1 


2 





1 


11 


52.5- 


62.5 


3 


2 


1 


1 


1 




















1 


1 


10 


62.5- 


72.5 





2 


2 


2 


1 





1 




















8 


72.5- 


82.5 






































1 


1 


82.5- 


92.5 








2 





1 





1 

















4 


8 


92.5- 


102.5 



































1 





1 


102.5- 


122.5 








1 























1 





1 


3 


122.5- 


142.5 



































1 


1 


2 


142.5- 


162.5 














1 











1 














2 


162.5- 


182.5 








1 





























1 


2 


182.5- 


202.5 






































2 


2 


> 202.5 

















1 














2 


1 


7 


11 


Total 
































negative 


242 


222 


102 


53 


28 


26 


15 


13 


4 


13 


35 


21 


33 


807 



288 



Table 116. Frequency distribution of number of fluctuations in horizontal intensity of various amplitudes 
and durations of five minutes or more. Copenhagen, December, 1932 



Duration, 
minutes 



0- 
10 



Number of fluctuations of amplitude in y from 



11- 

20 



21- 
30 



31- 

40 



41- 
50 



51- 
60 



61- 

70 



Total 



0- 
10 



11- 
20 



21- 
30 



31- 
40 



41- 
50 



51- 
60 



61- 
70 



Total 



Positive fluctuations 



Negative fluctuations 



5 - 7.5 


52 


4 


2 














58 


9 


1 





1 











11 


7.5- 12.5 


30 


12 


3 





1 








46 


4 


1 

















5 


12.5- 17.5 


18 


7 


4 





1 








30 


5 


2 

















7 


17.5- 22.5 


8 


1 


5 





1 








15 


3 


3 











1 





7 


22.5- 27.5 


14 


3 


2 


1 


2 








22 


7 


3 








1 








11 


27.5- 32.5 


9 


6 


7 





2 








24 


2 











1 








3 


32.5- 37.5 


1 


5 


1 


1 


1 


1 





10 


1 




















1 


37.5- 42.5 


3 


4 





1 











8 





2 


1 














3 


42.5- 47.5 





5 


4 


1 











10 





1 


1 














2 


47.5- 52.5 


2 


5 





1 


1 








9 





1 


1 














2 


52.5- 62.5 


2 


3 


1 


3 





1 





10 








1 


1 


1 








3 


62.5- 72.5 


1 


2 


2 














5 


1 


1 


2 








1 





5 


72.5- 82.5 





1 


2 





2 


1 


1 


7 





3 


1 


1 











5 


82.5- 92.5 





1 

















1 














1 








1 


92.5-102.5 





2 

















2 


























102.5-122.5 








1 


2 











•3 














1 








1 


122.5-142.5 





























1 

















1 


142.5-162.5 



































1 











1 


>162.5 














1 








1 



























Total 



140 61 



34 10 



12 



261 



32 



19 



60 







Table 117. Sensitiviti 


es and retu 


rn 


-ti 


me-constants of fluxmeters, 


College, Alaska 




Date 




B 


-fluxmeter 








Z -fluxmeter 








Return - 


time 


-constant 






Retu rn -time -constant 








Scale value 












Scale value 










+ 


- 


+ 


- 








y/mm 




sec 






sec 


y/mm 




sec 


sec 


Jul 


28, 


1942 a 


3.54 




35 






32 


4.42 




22 


25 


Aug 


31, 


1942 


3.52 




80 






104 


3.85 




51 


70 


Nov 


22, 


1942b 


3.52 




24 






22 


3.85 




32 


30 


Dec 


22, 


1942 


3.39 




28 






20 


3.97 




22 


27 


Jan 


26, 


1943 


3.39 




25 






22 


3.97 




30 


23 


Jan 


28, 


1943 


3.39 




40 






38 


3.97 




38 


3^ 


Apr 


23, 


1943 


3.49 




29 






28 


3.69 




20 


21 



^Basic element of Z -fluxmeter replaced August 3, 1942 
b Basic elements adjusted to reduce return-time-constant 



289 



Table 118. Resistances in ohms of H- and Z-coils, fluxmeter installation, ColJege, Alaska 



Date 


1 


2 


3 


4 


5 


1-5 










H-coil 






Jul 29, 


1942 


78.29 


78.43 


78.33 


78.43 


78.99 




Nov 17, 


1942 


75.00 


75.15 


75.07 


75.84 


76.41 


374. 0(?) 


Dec 4, 


1942 


74.82 


74.94 


74.87 


74.97 


74.90 


374.3 


Dec 21, 


1942 


74.62 


74.73 


74.66 


74.74 


74.71 


371.9 


Jan 26, 


1943 


74.27 


74.3 S 


74.33 


74.44 


74.76 


370.3 


Feb 25, 


1943 


74.16 


74.27 


74.20 


74.30 


74.85 


369.7 


Mar 30, 


1943 


74.07 


74.19 


74.12 


74.20 


74.76 


369.2 


ADr 14, 


1943 


74.12 


74.23 


74.16 


74.32 


74.34 


372.4 


Apr 23, 


1943 


74.19 


74.26 


74.17 


74.31 


74.35 


369.4 










Z-coil 






Jul 29, 


1942 


79.29 


79.04 


78.86 


79.08 


79.08 


390.82 


Nov 17, 


1942 


75.32 


75.00 


74.61 


74.80 


74.77 


373.0 


Dec 4, 


1942 


75.12 


74.75 


74.47 


74.65 


74.48 


372.1 


Dec 21, 


1942 


74.97 


74.60 


74.18 


74.48 


74.42 


371.2 


Jan 26, 


1943 


74.65 


74.31 


73.74 


74.18 


74.09 


369.6 


Feb 25, 


1943 


74.57 


74.25 


73.39 


74.11 


74.06 


369.2 


Mar 30, 


1943 


74.64 


74.31 


73.33 


• 74.20 


74.16 


369.4 


Apr 14, 


1943 


74.61 


74.28 


73.10 


74.17 


74.12 


369.3 


Apr 23, 


1943 


74.59 


74.27 


73.00 


74.16 


74.13 


369.4 



Table 119. Determination with standard mutual inductor of sensitivities of H- and Z-fluxmeters, 
College, Alaska; I = primary current in milliamperes 







Deflection (scale divisions) 


Maxwell- 


Element 


I 








turns per 












Positive 


Negative 


Mean 


division 


H 


50 


4.4 


4.45 


4.42 


11.32 




100 


8.75 


8.8 


8.78 


11.40 




150 


13.1 


13.4 


13.25 


11.32 




200 


17.2 


17.7 


17.45 
Mean 


11.47 
11.38 


Z 


50 


4.1 


4.1 


4.10 


12.21 




100 


7.9 


8.0 


7.95 


12.59 




150 


11.7 


12.0 


11.85 


12.65 




200 


15.4 


15.8 


15.6 
Mean 


12.82 
12.57 



290 



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5 £ H 

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3 co M 

o 3 S 
•c c o 

3.5 1 

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o.2 

sg 

g-a 

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co cm co co 



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oocmOio^oo 
oocmcmcmcocmo 



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CO 



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Ch n" £T co c? 02 t»< o 



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tJ< o t- 



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ococmcocococoo 



i-H CM rf" CM m csi 



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0000 



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cm - — • coO «9>—i- in- — . co- — • r-— - 00^ cr> i-i (_, 



291 



Table 121. Frequency distribution of fluctuations in vertical intensity of various amplitudes 
and durations measured at half -amplitude and also corresponding frequencies 
(in parentheses) roughly corrected for response defects of fluxmeter. 
College, Alaska, August, 1942 



Duration, 






■ 






Number 


}f fluctuations 


Of c 


implitude 


in y 


fro 


m 








seconds 


25 


-34 


35 


-44 


45 


-54 


55 


-64 


65 


-74 


75 


-84 


85 


-94 


95- 


104 


105 


-114 


Total 


















Positive fluctuations 














15-24 
(16-27) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 




(0) 


25-34 
(28-40) 


2 


(0) 





(2) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 


2 

(2) 


35-44 
(41-53) 


2 


(0) 


1 


(0) 





(2) 





(1) 





(0) 





(0) 





(0) 





(0) 





(0) 


3 

• (3) 


45-54 
(54-67) 





(0) 


1 


(0) 





(0) 





(0) 





(1) 





(0) 





(0) 





(0) 





(0) 


1 

(1) 


55-64 
(68-81) 


1 


(0) 


1 


(0) 


i 


(0) 





(1) 





(0) 





(1) 





(0) 





(1) 





(0) 


3 

(3) 


65-74 
(82-94) 


1 


(0) 





(0) 





(0) 





(1) 





(0) 





(0) 





(0) 





(0) 





(0) 


1 

(1) 


75-84 
(95-108) 


1 


(0) 





(0) 





(0) 





(0) 





(1) 





(0) 





(0) 





(0) 





(0) 


1 

(1) 


85-94 
(109-122) 


1 


(0) 





(0) 





(0) 





(0) 





(0) 





(1) 





(0) 





(0) 





(0) 


1 

(1) 


Total 


8 


(0) 


3 


(2) 


1 


(2) 





(3) 





(2) 





(2) 





(0) 





(1) 





(0) 


12 

(12) 


















Negat 


ive fluctuations 














15-24 
(16-27) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 




(0) 


25-34 
(28-40) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 




(0) 


35-44 
(41-53) 


l 


(0) 





(0) 





(1) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 


1 

(1) 


45-54 
(54-67) 


3 


(0) 





(0) 


1 


(3) 





(0) 





(0) 





(0) 





(1) 





(0) 





(0) 


4 

(4) 


55-64 
(68-81) 


3 


(0) 





(0) 





(0) 





(3) 





(0) 





(0) 





(0) 





(0) 





(0) 


3 

(3) 


65-74 
(82-94) 


1 


(0) 





(0) 





(0) 





(1) 





(0) 





(0) 





(0) 





(0) 





(0) 


1 

(1) 


75-84 
(95-108) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 





(0) 




(0) 


85-94 
(109-122) 


1 


(0) 


1 


(0) 





(0) 





(0) 





(0) 





(1) 





(0) 





(0) 





(1) 


2 

(2) 


Total 


9 


(0) 


1 


(0) 


1 


(4) 





(4) 





(0) 





(1) 





(1) 





(0) 





(1) 


11 

(11) 



292 



Table 122. Total number of fluctuations in horizontal intensity of various rates of change and 

durations measured at half-amplitude and also corresponding frequencies (in parentheses) 

corrected for response defects of fluxmeter, College, Alaska, August, 1942 



Duration, 














Numbe 


r of fluctuations with r 


ites of change 


in y/sec 










seconds 


0.4 


0.6 


0.8 


1.0 


2.0 


4.0 


6.0 


8.0 


10.0 


12.0 


16.0 


Total 






















Fluctuations, initial rate 














15-24 
(16-26) 





(0) 


2 


(2) 


1 


(1) 


2 


(2) 


12 


(12) 


3 


(3) 


1 


(1) 





(0) 





(0) 





(0) 





21 
(0) (21) 


25-34 
(27-38) 


1 


(1) 





(0) 





(0) 


11 


(11) 


28 


(28) 


5 


(5) 


2 


(2) 





(0) 





(0) 





(0) 





47 
(0) (47) 


35-44 
(39-50) 


3 


(3) 


4 


(0) 


5 


(4) 


18 


(23) 


26 


(26) 





(9) 





(0) 





(0) 


1 


(0) 





(1) 





66 
(0) (66) 


45-54 
(51-63) 


3 


(0) 


4 


(3) 


5 


(4) 


22 


(27) 


14 


(14) 


1 


(0) 


2 


(H 





(2) 





(0) 





(0) 





51 
(0) (51) 


55-64 
(64-76) 


9 


(0) 


7 


(9) 


13 


(7) 


19 


(32) 


27 


(27) 


3 


(0) 





(3) 





(0) 





(0) 


1 


(0) 





79 
(1) (79) 


65-74 
(77-89) 


6 


(0) 


10 


(6) 


11 


(10) 


15 


(26) 


13 


(13) 


6 


(0) 





(6) 





(0) 





(0) 





(0) 





61 
(0) (61) 


75-84 
(90-103) 





(0) 


4 


(0) 


5 


(0) 


11 


(9) 


8 


(11) 





(8) 





(0) 





(0) 


11 


(0) 





(0) 





28 
(0) (28) 


85-94 
(104-117) 





(0) 





(0) 





(0) 


1 


(0) 


1 


(1) 


1 


(1) 





(1) 





(0) 





(0) 





(0) 





(0) (3) 


Total 


22 


(4) 


31 


(20) 


40 


(26) 


99 


130) 


129 


132) 


28 


(26) 


5 


(14) 





(2) 


1 


(0) 


1 


(1) 





356 
(1) (356) 






















Fluctuations, 


recovery 


rate 














15-24 
(16-26) 





(0) 


1 


(1) 





(0) 


1 


(1) 


17 


(17) 


1 


(1) 


1 


(1) 





(0) 





(0) 





(0) 





21 
(0) (21) 


25-34 
(27-38) 


1 


(1) 


1 


(1) 


4 


(4) 


13 


(13) 


20 


(20) 


8 


(8) 





(0) 





(0) 





(0) 





(0) 





47 
(0) (47) 


35-44 
(39-50) 


5 


(5) 


2 


(2) 


3 


(3) 


16 


(16) 


32 


(32) 


2 


(2) 


3 


(3) 


1 


(1) 


1 


(1) 





(0) 





65 
(0) (65) 


45-54 
(51-63) 


1 


(1) 


4 


(4) 


7 


(7) 


17 


(17) 


20 


(20) 


1 


(1) 


1 


(1) 





(0) 





(0) 





(0) 





51 
(0) (51) 


55-64 
(64-76) 


6 


(6) 


8 


(8) 


17 


(17) 


21 


(21) 


21 


(21) 


4 


(4) 


2 


(2) 





(0) 





(0) 





(0) 





79 
(0) (79) 


65-74 
(77-89) 


11 
(11) 


7 


(7) 


10 


(10) 


21 


(21) 


11 


(11) 


1 


(1) 





(0) 





(0) 





(0) 





(0) 





61 
(0) (61) 


75-84 
(90-103) 


4 


(4) 


2 


(0) 


6 


(2) 


12 


(18) 


3 


(3) 


1 


(1) 





(0) 





(0) 





(0) 





(0) 





28 
(0) (28) 


85-94 
(104-117) 





(0) 


1 


(0) 





(1) 





(0) 


1 


(1) 


1 


(0) 





(V 





(0) 





(0) 





(0) 





(0) (3) 


Total 


28 
( 


28) 


26 


(23) 


47 


(44) 


101 

(107) 


125 

(125) 


19 


(18) 


7 


(8) 


1 


(1) 


1 


(1) 





(0) 





355 
(0) (355) 



293 



Table 123. Total number of fluctuations in vertical intensity of various rates of change and 

durations measured at half -amplitude and also corresponding frequencies (in parentheses) 

corrected for response defects of fluxmeter, College, Alaska, August, 1942 



Duration, 
seconds 



0.4 



0.6 



Number of fluctuations with rates of change in y/sec 



0.8 



1.0 



2.0 



4.0 



6.0 



8.0 



10.0 12.0 



16.0 Total 



15-24 
(16-27) 

25-34 

(28-40) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



Fluctuations, initial rate 



(0) 



(0) 







CO) 



(0) 







(0) 



(0) 







(0) 



(0) 



10) 



(0) 



(0) 



(0) 





(0) (0) 



(0) (0) 



35-44 
(41-53) 



(0) 



(0) 



(0) 



(1) 



(2) 



(0) 



(0) 



(0) 



(0) 



(0) 



3 

(0) (3) 



45-54 
(54-67) 



(0) 



(0) 



(1) 



(5) 



(1) 



(0) 



(0) 



(1) 



(0) 



(0) 



8 

(0) (8) 



55-64 
(68-81) 

65-74 
(82-94) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



(2) 



(0) 



(3) 



(2) 



(1) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



6 

(0) (6) 

2 

(0) (2) 



75-84 

(95-108) 



(0) 



(0) 



(0) 



(1) 



(0) 



(o) 



(0) 



(0) 



(0) 



(0) 



1 

(0) (1) 



85-94 
(109-122) 

Total 



(0) 



(0) 



(0) 



(0) 



(0) 



(2) 



(1) 



(0) 



(0) 



(0) 



(0) 



3 

(0) (3) 



(0) 



(1) 



11 



(9) 



5 10 

(10) (2) (0) (1) 





(0) (0) 



23 

(0) (23) 



Fluctuations, recovery rate 



15-24 
(16-27) 



(0) 



(0) 



(0) 



(0) 



(0) 







(0) 







(0) 







(0) 



(0) 



(0) 





(0) (0) 



25-34 
(28-40) 



(0) 



(0) 



10) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 





(0) (0) 



35-44 
(41-53) 



(0) 



(0) 



(0) 



(1) 



(2) 



(0) 



(0) 



(0) 



(0) 



(0) 



3 

(0) (3) 



45-54 
(54-67) 



(0) 



(0) 



(2) 



(4) 



(2) 



(0) 



(0) 



(0) 



(0) 



(0) 



8 

(0) (8) 



55-64 
(68-81) 



(1) 



(0) 



(1) 



(3) 



(J) 



(0) 



(0) 



(0) 



(0) 



(0) 



6 

(0) (6) 



65-74 
(82-94) 



(0) 



(0) 



(1) 



(1) 



(0) 



(0) 



(0) 



(0) 



(0) 



(0) 



2 

(0) (2) 



75-84 
(95-108) 



(0) 



(0) 



(1) 



(0) 



(0) 



(0) 



(0) 



10) 



(0) 



(0) 



1 

(0) (1) 



85-94 
(109-122) 

Total 



(0) 



(1) 



(0) 



(2) 





* (0) 



(0) 



(0) 



(0) 



(0) 



(0) 



3 

(0) (3) 



(1) 



(1) 



(5) 



(11) 



5 

(5) (0) (0) (0) 





(0) (0) 



23 

(0) (23) 



294 



Table 124. Number of fluctuations for each GMT hour, College, Alaska, August, 1942 



Hour, 
GMT 










Number of fluctuati 


ons of 


amplitude in y 


from 










25- 


35- 


45- 


55- 


65- 


75- 


85- 


95- 


105- 


115- 


125- 


135- 


145- 


195- 


Total 




34 


44 


54 


64 


74 


84 


94 


104 


114 


124 


134 


144 


194 


254 
















Horizontal ir 


itensity 














h h 
































00-01 


1 





























G 











1 


01-02 


3 


1 





2 
































6 


02-03 


1 


3 


1 



































5 


03-04 


3 


8 


2 



































13 


04-05 


5 


1 


2 


3 


1 


1 


























13 


05-06 


3 


1 






































4 


06-07 


4 


4 


1 


1 





1 


























11 


07-08 


9 


4 


2 


4 





























1 


20 


08-09 


12 


15 


3 


4 








1 








1 














36 


09-10 


4 


5 


5 


1 





2 


2 


2 


1 


1 














23 


10-11 


8 


15 


5 


3 


2 


3 





1 





p 











1 


40 


11-12 


10 


18 


4 


7 





2 





i 




















4.? 


12-13 


10 


12 


2 


2 


1 


1 

















J 








29 


13-14 


10 


7 


3 








1 


























21 


14-15 


3 


1 






































4 


15-16 


3 


9 


5 


2 


1 


2 














1 











23 


16-17 


6 


4 


1 


5 


1 


2 





1 





o 














20 


17-18 


5 


1 


1 


1 


3 


2 





6 











9 








13 


18-19 


3 









































3 


19-20 





1 


2 


2 





2 





i 




















8 


20-21 





3 






































3 


21-22 


4 


1 





1 














o 

















6 


22-23 


5 


2 


1 














o . 




















8 


23-24 


1 


2 








1 





























4 


Total 


113 


118 


40 


38 


10 


19 


3 


6 


1 


4 


1 


1 





2 


356 
















Vertical intensity 














00-01 















































01-02 





1 






































1 


02-03 















































03-04 















































04-05 















































05-06 















































06-07 















































07-08 


2 


1 


1 



































4 


08-09 















































09-10 


3 









































3 


10-11 


2 









































2 


11-12 


2 









































2 


12-13 


2 









































2 


13-14 


1 


1 






































2 


14-15 















































15-16 


3 


1 


1 



































5 


16-17 


2 









































2 


17-18 















































18-19 















































19-20 















































20-21 















































21-22 















































22-23 















































23-24 















































Total 


17 


4 


2 



































23 



295 



Table 125. Summary of largest positive and negative fluctuations durations 

less than 150 seconds, horizontal intensity, H-fluxmeter, College 

Alaska, November 1, 1943, to January 31, 1944* 



Date 



Amplitude 



Rate of 
change 



Date 



Amplitude 



Rate of 
change 



1943 


r 


r/sec 


1943 


y 


y/sec 


Oct 8 


+ 139 


+ 6.9 


Dec 17 


+ 182 


+ 5.9 




-268 


-6.9 




-254 


-4.8 


Oct 11 


+ 187 


+ 6.6 


Dec 21 


+ 307 


+ 7.6 




-303 


-4.8 




-166 


-5.3 


Oct 25 


>+210 


+ 3.7 


Dec 22 


+ 203 


+ 5.5 




-299 


-5.5 




-294 


-5.4 


Oct 27 


? 


? 


Dec 28 


+ 187 


+ 3.0 




<-288 


-9.6 




-244 


-3.1 


Nov 20 


+ 230 


+ 6.7 


1944 








-306 


-5.2 


Jan 10 


+ 268 


+ 5.9 


Nov 23 


+ 204 


+ 5.4 




-214 


-5.9 




-147 


-3.8 


Jan 12 


+ 84 


+ 2.4 


Nov 25 


? 


? 




-168 


-2.8 




-200 


-5.5 


Jan 14 


+ 162 


+ 3.4 


Nov 26 


+ 119 


+ 6.7 




-142 


-2.8 




-220 


-4.3 


Jan 17 


-183 
+ 66 


+ 4.1 
-2.4 



♦Prepared by C. W. Malich, College Magnetic Observatory 



296 



FIGURES 129-226 

Figure Page 

129. La Cour horizontal-intensity variometer 299 

130. La Cour declination variometer '. 299 

131. La Cour vertical-intensity variometer 299 

132(A)-(B). Magnetograms, Petsamo, Finland, May 17-18, 1933 300 

133-134(C). Responses of la Cour variometers 301 

135-137. Beats near resonance frequency, D-, H-, and Z-variometers 303 

138(A)-(B). Response of D-, H-, and Z-variometers to sinusoidal fields of periods four and 

nine seconds, initial response and steady response 305 

139. Response of D-, H-, and Z-variometers to suddenly impressed field of constant value . . 306 

140(A)- (B). Micropulsations at Lycksele, Sweden 307 

140(C). Giant pulsations at Abisko, Sweden, and Tromso, Norway 307 

141. Beat-responses of variometers for intermittent sinusoidal fields of one-half minute 
duration appearing at successive three-minute intervals, D, H, and Z 308 

142. Responses near resonance frequency, D, H, and Z 308 

143. Artificial disturbances, D, H, and Z 308 

144. Comparison of computed responses near periods of resonance of D-, H-, and Z-variom- 
eters with corresponding impressed fields 308 

145. Comparison of computed responses of D-, H-, and Z-variometers with corresponding 
impressed fields of periods four and nine seconds 308 

146. Variation in response characteristics of variometers with various damping factors .... 309 

147. Northern and southern zones of maximum auroral frequency, equator for centered 
dipole, and magnetic stations selected for discussion of geographical distribution of 

ranges in H, D, and Z 309 

148(A)-(C). Frequency distributions of daily ranges in horizontal intensity (H), vertical inten- 
sity (Z), and magnetic declination (D) at various magnetic observatories, 1932-33 310 

149. Estimated percentage frequency of days with occurrence of aurora, clear nights, 

Northern Hemisphere 311 

150-151. Frequency distributions of daily ranges in H and Z, Sitka, 1905-26, and Cheltenham, 

1905-30, and corresponding values, September, 1932, to August, 1933 312 

152. Frequency distributions of ranges for magnetic storms, Bombay, 1882-1905, and Sloutzk, 
1878-1940 313 

153. Frequency distributions by months of daily ranges in horizontal and vertical intensities, 
Cheltenham, 1905-30 313 

154. Probability that daily ranges of H, D, and Z exceed various magnitudes, 1932-33 314 

155. Variation with latitude of expectations in davs for ranges in excess of various magni- 
tudes in H, D, and Z 315 

156-161. Isochronic lines for expectation in days before daily ranges in H, D, and Z exceed 

200y and lOOOy, 1932-33 316 

162. Geographic and geomagnetic co-ordinate systems for entire Earth 319 

163. Lines of equal geomagnetic latitude 319 

164-166. Daily maxima and minima horizontal intensity, declination, and vertical intensity, 

Sitka, Alaska, September 1, 1932, to August 31, 1933 320 

167. Probability that daily and weekly ranges of H, D, and Z exceed various magnitudes, 

1932-33 323 

168(A)- (D). Probability that ranges in H, D, and Z during given time -intervals exceed various 

magnitudes, Tromso, 1930-37, Sitka, Cheltenham, and Honolulu, 1905-30 325 

169-171. Isochronic lines for expectation in three-month periods before three-monthly ranges 

in H, D, and Z exceed 500y 326 

172-174. Isochronic lines for expectation in weeks before weekly ranges in H, D, and Z 

exceed lOOOy 327 

175-177. Isochronic lines for expectation in months before monthly ranges in H, D, and Z 

exceed lOOOy 329 

178-180. Isochronic lines for expectation in three-month periods before three-monthly 

ranges in H, D, and Z exceed lOOOy „ 330 

181-183. Isochronic lines for expectation in six-month periods before six-monthly ranges 

in H, D, and Z exceed lOOOy 332 



297 



298 THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



FIGURES 126-226 --Concluded 

Figure Page 

184-186. Isochronic lines for expectation in years before yearly ranges in H, D, and Z 

exceed lOOOy 333 

187-188. Isochronic lines for expectation in three-month periods before three -monthly ranges 

in H and D exceed 1500y 335 

189-191. Belts near each auroral zone in which average probability is at least 0.1 that total 

three -monthly ranges in H, D, and Z equal or exceed lOOOy 336 

192. Frequencies of fluctuations of various amplitudes in gammas and durations in seconds, 

H, D, and Z, Petsamo, August 1 to October 31, 1932 . 337 

193-194. Frequencies of fluctuations in H, D, and Z having various rates of change in gammas 

per second and semidurations, Petsamo and Copenhagen, 1932-33 338 

195-196. Monthly frequencies of fluctuations in H, D, and Z having various rates of change in 

gammas per second and semidurations, Petsamo and Copenhagen, 1932-33 339 

197. Variation with latitude of frequencies of fluctuations of various durations, 10 to 500 sec- 
onds, H, D, and Z, mean of six days 340 

198. Variation with geomagnetic latitude of magnitude of total impulse for fluctuations of 
duration 10 to 500 seconds for days of various magnetic character figures C 341 

199. Variation with geomagnetic latitude of daily frequency of fluctuations, durations 10 to 500 
seconds, H, D, and Z, for various values of magnetic character figure C 342 

200. Hourly variation with geomagnetic latitude of frequency of fluctuations, durations 10 to 

500 seconds, H, D, and Z 342 

201. Variation with geomagnetic latitude in hourly frequency of positive and negative fluctua- 
tions, durations 10 to 500 seconds, H, D, and Z, mean of six days 343 

202. Variation with geomagnetic latitude of magnitude of total impulse, for fluctuations of 
duration 10 to 500 seconds 344 

203-205. Isomagnetic lines for amplitude of fluctuations in H, D, and Z, to 150 seconds' 

duration, with average probability of 0.1 for three-month intervals 344 

206-209. Latitude distributions of maximum disturbance vectors of small fluctuations, view 

from above geomagnetic north pole 346 

210. Geomagnetic effects lightning discharges, Huancayo, Peru 349 

211-212. Response to impressed field 0.01 of various periods, H- and Z-fluxmeters, College, 

Alaska, August, 1942 350 

213. Response in scale -divisions of G. E. fluxmeter No. 725024 to single-cycle fields of 

various amplitudes and periods 351 

214. General view, University of Alaska, showing approximate location of fluxmeter installa- 
tion 351 

215. Cheltenham Magnetic Observatory: (A) Location of buried fluxmeter coils and flux- 
meters, (B) Fluxmeters and control apparatus 351 

216. Constructional details of H- and Z-coils, College, Alaska 352 

217. General plan, storm-recorder installation 352 

218. Schematic diagram of electrical circuit, fluxmeter installation 352 

219-221. Simultaneous fluxmeter records on magnetically quiet day, April 8, 1943, and mod- 
erately disturbed days, February 17 and April 8, 1943, College, Alaska, and Cheltenham, 
Maryland 353 

222. Fluxmeter records of unusual character, November 24, 1942, College, Alaska 354 

223. Short-period geomagnetic fluctuations of large amplitude and short duration, Mgtut, 
Greenland 355 

224. Typical record portable magnetograph operated at high sensitivity, Turtle Mound, Florida 355 

225. General view of CIW portable magnetograph 355 

226. CIW portable magnetograph showing quartz fiber double-suspension universal detecting 
element and mount 355 




Fig. 12P. I_a Cour horizontal-intensity 
variometer 



Fig. 130. La Cour declination variometer 




Fig. 131. La Cour vertical-intensity variometer 
299 







$< 




^/G. 132 (A) —\QUICK-RUN MAGNETOGRAM, PETSAMO, FINLAND, MAY 17- IS, 1933 (ORIGINAL TIME-SCALE ISO Mm/hOUr) 



it ^ /' 



-7 1 



I M 



-?--4~-.<$ 







PETSAMO, 1933, MAY 17 , S h 30 m 
TO MAY IB, S h OS r " 



w*' 







? /<? /z /V /S /g Jtt U, > JbC . £ V C 



IV 



V. 



II 



£ <? 



/» 



/^ ^ /g 20 4S* 



/■w */-».-. 



^ v. ^ £ ; <r 



»/ 



FIG. 132(b) — MAGNETOGRAM, PETSAMO, FINLAND, MAY 17-18,1933 (ORIGINAL TIME-SCALE IS Mm/hOUR) 



300 



V V V 



K=0.0t4S, p-3.105 




DECLINATION 



H'0.0213, p-3.58 




HORIZONTAL INTENSITY 



h-0.0275, p'3.83 




VERTICAL INTENSITY 



FIG. 133 — RESPONSE OF LA COUFt D-, H-, AND Z-VAPIOMETERS AFTER SUDDEN IMPULSE 



301 



. A 

A !\ H 



'i !\ fi 



X-2 SECONDS 



r v l / / I 



I i A 



[j l' \! 1 1 1 1/ \/ * " 



A ,~ A, A 

V a ^~ V x - 



, 4 A=J SECONDS 

A=* SECONDS 



A = / SECOND 



k=2 SECONDS 



A r, a 



*. A A A A A , A . '' '"• '" ■ A r. /. 



'\ '\ <\ '" " ' 



/\/\/vyyi/vyv^^v^ 



\A/ 



X/ v/^-N 



A=J SECONDS 

w ^' V/ ^, ' \y vy 

A=« SECONDS 
< J V -'X/ >V — H»/\ AN ''"\ 



a jo 



f/S. 134(A)— RESPONSE OF LA COUR D-VARIOMETER TO SINUSOIDAL MAGNETIC FIELDS; (a) INITIAL RESPONSE, AND (b) STEADr RESPONSE 



!• f A ■ a *■ ' ueoue 



li t\ A 

1 I' ' 



a ; : 



1 1 



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A, 

' I 1 



I I 1 II r™ 

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iiUifVi 



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I ' \ /\ ' \ / 



A/\A,A 



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v v 



A A A - ^ M /\ M /\ ; 

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. . X' l SECONDS 

k a * /\ A - A A A ' '. » » f 

il ii ii ii ii ii 'i ii i c , h 



C f;i... 



I I 



y « ii n d v n i; ^ 



■» — r 



*"J SECONDS 



A A A A a A A a A A A A 

\l\jy v v ^ v \j \j v/ v ■■ 

\*4 SECONOS 

\A A A A A A A a 



w 



SC*t£ W SECONDS 



SCALE IN SECONOS 

1 ., ., ? .,..'}.. , 



FIG 134(B)- RESPONSE OF LA COUB M-VARIOMETCR TO SINUSOIDAL UACNCTIC FIELDS; M INITIAL RESPONSE, AND (b) STEADr RESPONSE 



h 1 -. / \ ;.a WA^/Hnv, 



H 



i I 



A: 

i 
-J W- 



i ■ i 



I ! 



! l / 



\- 



A A J 



HA\AAAAAy\AAA< 

^ v v/ 



v v -/ v \; ^ v v 



A A 



^ / A /\ ^ /\ A \ 



V V 



A ' * " .' " " ' * " " " \ r.. ". a A a « ;, p " . r, a ", ;■ ," .■> ,". A 1 /• '. / 

i/Vrfll»»»i,»»«"ir»V,'\/ 1 /VvV'-V-w' *iJJ'J',Ji 

i.^lliiir"! ft ii II ii 



l r,| i)lA 



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*\ A A A A A A A A A A A 
\ I \ i \ A ' \ ' \ ' \ i \ i \ ' \ ' \ i 
^ i \ 1 \ i \ i \ I \ I \ i \ i \ I \ i . i 
\J \J \J V ^ \J \J \J \J \j 



i j 



A«« trconos 



I \ I l / \ ' v / \ I \ I \ I \ I 

\J \J V \J \J \J \/ \.> \j 



<tt 



KALE W SECONDS 

9 .... i . . . V . . . . if . . . TV . . . . # V 



SCALE 1 SECONOS 
. t . . . . V . ...*.. . . V . . . . V . 



FIG. 134 (C)-ReSPONSe Of LA COUFt Z-mntOMCTCK TO SINUSOIDAL MMMCTIC FIELDS; (I) INITIAL RCSPOMSf, AW (b) iTCAOf fiCSPOMU 

302 



srnnro Ml sms 



i i § 




0731 J OlSSJadm JO 30nil7dH\r 



WWW * tiros 



I . g . 8 . 8 . § . y 



5 i > L ^> --> . 5 8 S - 

S c > <- — ^ > i S S ^-v 

r L — » '-"^"m - -^"■ > ,r ~"- < - ' ~~ " 

-— * — ., -- _--* - -, <■ . - - *-—_ 

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— — — T 



88 






07»./ oissiuam jo 30njnanr 



303 



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■II 'II ,' V 



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\=/.40 SCCONOS 



jt-([4» *-tH ^r< t^- 



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A=/.« SECONDS 

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f/G. 137 -BEATS NCAfi f*LSONANCC-ff*£Qu£NCr, 2 -VARtOM£T£R 



304 



am 



/>. , r i A A 



\ 






., , AAA' \i 

\ \ j \ I J DECLINATION \j \ ' 




^ A A A A f\ A A f 



J V \J 



DECLINATION 



f\ r \ A A f 



\l \l \l \l \J V \J \! 



HORIZONTAL INTENSITY 



\ l\ I \ I \ I \ / \ / \ / \ / 

\ / \ ' \ ' \ ' \ I \ ' \ I \ I 

VERTICAL INTENSITY 



SCALE IN SECONDS 



SCALE IN SECONDS 



FIG. 13$ (A) -RESPONSE OF D, H, AND Z LA COLIN VARIOMETERS TO SINUSOIDAL FIELD OF PERIOD 4 SECONDS; (a) INITIAL RESPONSE, AND (b) STEADY RESPONSE 



k-~ 



\ / 



/-\ r 



/ 



DECLINATION 



1 ^ / 



r^' 



A A , 



K 



/ 



\y 



^ 



HORIZONTAL INTENSITY 



/ 



/ X / 



/ - 



DECLINATION 



\ J V / 



7 \ / \ / \ ' 

l\ I \ I \ f 



I 



/ 


\ 


\J 


\/ 




L UZONTAL INTENSITY 




FIG. 138(B) — RESPONSE Of D, H, AND Z LA COUR VARIOMETERS TO SINUSOIDAL FIELD OF PERIOD 9 SECONDS; (a) INITIAL RESPONSE, AND (b) STEADY RESPONSE 



305 



A n 



DECLINATION 




HORIZONTAL INTENSITY 




\j V 1/ W « v 



/I /I ii 



VERTICAL INTENSITY 




SCALE IN SECONDS 
... ... ■ 



306 



DECL IN A TION 



-I 1 — t~ \ 



H — I — \ 




H — I — I — I — h 



^ 



HORIZON TAL IN TENSI T 



ft-H — V 



i=mffm 



VERTICAL INTENSI) 



1. 1 . 1 



I ' l . 1 . I , 1 ' I I 




-t- I 



(/>) MARCH 8, 1933 



DECLINATION 




w,-i-..i .t—t- 



Itt-rK- 4— C 



i i i 



HORIZON TAL IN TENSI T 



1 — I — h-4 
-4-4-4- 



VERTICAL INTENSITY 



JLJ. 



I — I — h 



:#^J==±~ 



r /(W J 
so * 

L £7 -j 



IffH — I — Y 



(B) JUNE 26, 1933 



FIG. I40(A)AND (B)— MICROPULSAT IONS AT LYCKSELE, SWEDEN (LAT. 64° ' 3t'.0 N , LONG. 18° 4o!? E); TIME 

INDICATED IN HOURS, GMT 



■hSKi 



§ Special 
■^ time-rrlark 



ABISKO 
September 10,1930 




ABISKO 
September 12,1930 



"S&±?M^-- 




22" GMT Z 23 h GM7 Z T Zj 



h GMT Z 8 h GMT Z Z ^ 




FIG. I4-0(C)-GIANT PULSATIONS AT AB/SKO, SWEDEN (LAT. 6S.°4 N, LONG. I8?8 E), AND TROMSO, 

NORWAY (LAT. 69° 7 N, LONG. I8°9 E) 



307 



LLLkd 

ffTT 



DECL INA TION 



HORIZONTAL INTENSITY 



VERTICAL INTENSITY 



F/G /4/ -BEAT-RESPONSES OF VARIOMETERS FOR INTERMITTENT SINUSOIDAL FIELDS OF 
ONE-HALF MINUTE DURATION APPEARING AT SUCCESSIVE THREE-MINUTE INTERVALS, 0, 

AND Z 



DECL I NAT ION 



m 

HORIZONTAL INTENSIT 



VERTICAL INTENSITY 



FlC iaZ —RESPONSES NEAR RESONANCE-FREQUENCY, 0, H, AND Z 



DECLINATION 



HORIZONTAL INTENSITY 



VERTICAL INTENSITY 





FIS. IIS -COMPARISON OF computed responses (full lines) of d-,h-,and z- 
VARIOMETERS WITH CORRESPONDING IMPRESSED FIELDS s-CK(l-COS mtJ/M 
(BROKEN LINES) OF PERIODS 4 AND 9 SECONDS 



FIG. 144— COMPARISON OF COMPUTED RESPONSES (FULL LINES) NEAR PERIODS OF 
RESONANCE OF D-, H-, AND Z-VARIOMETERS WITH CORRESPONDING IMPRESSED 
FIELDS S =CK (/-COS mt) / M (BROKEN LINES) 



308 




— T 

PERIOD IN SECONDS 



1 T 

PERIOD IN SECONDS 



FIG I4&-VARIATI0N IN RESPONSE-CHARACTERISTICS OF VARIOMETERS WITH VARIOUS DAMPING FACTORS A FOR n? = IO: (A) RESPONSE TO SUDDENLY IMPRESSED FIELD 

YIFI DING 01 RADIAN TRUE DEFLECTION; (B) VARIATION WITH K OF AMPLITUDE-RATIO, OBSERVED TO TRUE RESPONSE, FOR SINUSOIDAL IMPRESSED FIELDS OF 

CONSTANT AMPLITUDE AND PERIOD; AND (C) CORRESPONDING LAGS IN PHASE OF RESPONSE RELATIVE TO IMPRESSED FIELDS OF (A) 




FIB. /47-NORTHERN AND SOUTHERN ZONES OF MAXIMUM AURORAL FREQUENCY, EQUATOR FOR CENTERED DIPOLE , AND MAGNETIC STATIONS 
SELECTED^ FOR DISCUSSION OF GEOGRAPHICAL DISTRIBUTION OF RANGES IN H, D, AND Z 



309 




FIG I48(4)-FREQUENCY-DISTRIBUTI0NS OF DAILY RANGES IN HORIZONTAL INTENSITY (h) AT VARIOUS MAGNETIC OBSERVATORIES, II MONTHS 

OF POLAR YEAR (AUGUST 1932 TO AUGUST I933J 




FIS.I4-8{P)-FRE0UENCY-0ISTRI8UT/0NS OF DAILY RANGES IN VERTICAL INTENSITY (z) AT VARIOUS MAGNETIC OBSERVATORIES, 12 MONTHS 

OF POLAR YEAR (AUGUST 1932 TO AUGUST 1933) 



310 




r/G./aa-csriMArro Pd>C€NrAO€-rReoucNCy or DArs with occurucncc or a<j/>ooa i cl£ar nights, northcrh hcmispkrc 



311 



21 


W * 


W 600 000 1000 
SCALE IN GAMMAS 


1200 


1400 


1 
















1 


























HORIZONTAL INTENSITY 






























T 






































* 

§ 




























• OBSERVED VALUE, 1905-26 










1 






" CORRESPONDING VA 


-UE, 1932 


33(i 


") 






1 ^ 














" 


. 
























































^ I3O0- 






































X 








VERTIC 


AL INTEN^ 


ITY 










* 

i 

i 


V 




































\ 






*' 




■ 




' 







FIG. ISO -FREQUENCY-DISTRIBUTIONS OF DAILY RANGES IN H AND Z, SITKA, 
1905-26, AND CORRESPONDING VALUES (X 22), SEPTEMBER, 1932, TO 
AUGUST, 1933 





« 


K 


AC 


v aoo too 

SCALE IN GAMMAS 1 


10 


00 




21 


W 


AC 


V 6C0 A 

SCALE IN GAMMAS 


» 10 


OO 






































' 


.' 




HORIZON Ta 


IL INTCNSI 


TY 


■ 






VERTICAL 


INTENSITY 










































T 




































i 

A 














' 












r 


1 


























• omsERy 


EO VALUE, I9C 


3-30 
































o ooMtes 


PONDING VALU 


f, 1 032 33 (x 26 


> 




\ 


S, 










■ 


I 




. 






■ 



FIO. 151 -FREQUENCY-DISTRIBUTIONS OF DAILY RANGES IN H AND Z, CHELTENHAM, 1905-30, AND CORRESPONDING VAL- 
UES (X 26), SEPTEMBER, 1932, TO AUGUST, 1933 



312 



200 400 eoo 900 1000 12 


K 1400 1600 1900 


r\ 






SCALE IN GAMMAS 

\ | 


1 1 
COL ABA, BOMBAY 




















11 


h — . 




HORIZONTAL INTENSITY 










A 


■ 












SLOUTZK 




,„. 


/ 1 
















.00 


/ 






HORIZONTAL INTENSITY 










/ 


















50- 


/, 




^^^ . . 














X,OO j7 


I 


















H /30- 




















* 








DECLINATION 










I 








- | 


, 


1 


, 


, 


£ 50- 


/~\ 
















■100 








VERTICAL INTENSITY 












Vr 
















so 



FIG. /Si —FREQUENCY -DISTRIBUTIONS OF RANGES FOR MAGNETIC STORMS GREATER THAN 70f IN 
H, 34- TO 77-HOUR INTERVALS, BOMBAY, 1882-1905, AND OF DAILY RANGES FOR STORMS GREATER 
THAN 60? IN 0, SLOUTZK, 1878-1940 



ZOO 400 600 800 

SCALE IN GAMMAS 



HORIZONTAL INTENSITY 



ZOO 400 600 BOO 

SCALE IN GAMMAS 



VERTICAL INTENSITY 




.: • ' , \>RtR 



NOVEMBER 



DECEMBER 



FIG. 153 -FREQUENCY-DISTRIBUTIONS BY MONTHS OF DAILY RANGES IN HORIZONTAL AND VERTICAL 
INTENSITIES, CHELTENHAM, 1905-1930 



313 



\ 


X) St 

SCALE >S 

IPlZONTAl 


X) 12 

GUMMAS 

INTZHSI 


TO 
TY 


\ * 


■Hi SOO IA 

SCALE IN GAMMAS 

1 

DECLINATION 

THULE 


oo 


V 


X) Si 
SCALE IN 

RTICAL II 


GAMMAS 
VTENSITV 


oo 












GODHAVN 






















BEAU ISLAND 






















,. JULtANNEHAAB 






















v EORT 


RAE 

L 






















TROMSO 






















PETS A 


wo 






















SODANK 


'LA 












L 










SITKA 














I 








I 


RUDE 


"KOV 




I 


















CHEL Tt 


'NHAM 




^ 


















rues 


ON 




k. 
















\ 


HONOL 


ULU 












\ 










HUANC 


Aro 




















\ 


PILAR 














A 










WAT HE I 


?oo 




\ 








I 










SOOTH ( 


~>RKN£YS 

■ ■ 













flO I.IS4— PROBABILITY THAT DAILY RANGES OF H, D, AND 2 EXCEED VARIOUS MAGNITUDES, IZ MONTHS, 133! -33 



314 



t 


0% jo*' b* jo" t 

GEOMAGNETIC LATtTUOE 


o°s 


t 


G£OMAGN£TtC laTITUOE 


»*s 


( 


O a N ' J0° ' 6" 30* t 
GEOMAGNETIC LATITUDE 


<>V 




I I I 






I I I 












I 
HORIZONTAL INTENSITY (h) 






DECLINATION (0) 






VERTICAL INTENSITY (z) 




■ISO 


















































SO GAMMAS 


















so 


























^ 


r 


■\ 
































-J 






1" 




ISO 
















100 GA 


HMAS 












































/ 






\ 




so 








■ 












\ 






7 






\ 


















*1 1 






■v 






6 






A 


















1 












i : 
























/ 


























































ISO 


f 












/ 


ISO GA 


MM AS 




















/ 












/ 












j_ 










so 


/ 












/ 






■V 












\ 




l! 














T 






r 






t 












■200 5 - 














/ 






\ 






i 






I 


































o 














/ 






■ 






i 










-IS0% 


V 














200 GAMMAS 


■ 
























■so 














/ 






\ 






/ 










' 1 II II* 


r^ 


— 


— 


— 




***** 


/ 


— - 


— 


\ 




h"" 1 


/ 


— — 


— 


\ 


w7 


■zoo 

ISO 
















soo c> 


1MMAS 


















r 




, , 


, , 




U 


\j 










J 


I 


; 




, 




, . 


v. 


1 


1 
















/000 G/ 


MM AS 






















-u 










\! 
















9 










J 





FfG. 153- VARIATION WITH LATITUDE OF EXPECTATIONS IN DAYS FOR RANGES IN EXCESS OF VARIOUS MAGNITUDES, IN H, D, AND Z 
LEGEND: « -POLAR YEAR, lg MONTHS, /ftV-J»; ° =SlTHA, ISOS-26; 0-SLOUT2K, 1878-1939, a -CHELTENHAM, /90S-30; • -BOMBAY, 1862-190$ 



315 




FIG.IS6-ISOCHRONIC LINES FOR EXPECTATION IN DAYS BEFORE DAILY RANGE IN H EXCEEDS 2007, 12 MONTHS, 1932-33 




FIG.IS7-IS0CHR0NIC LINES FOR EXPECTATION IN DAYS BEFORE DAILY RANGE IN\0 EXCEEDS 2007, 12 MONTHS, 1932-33 



316 




FIG. 158— ISOCHRONIC LINES FOR EXPECTATION IN DAYS BEFORE DAILY RANGE IN Z EXCEEDS 200/, 12 MONTHS, 1932-33 




F/G. 159 -ISOCHRONIC LINES FOR EXPECTATION IN DAYS BEFORE DAILY RANGE IN H EXCEEDS lOOOy, 12 MONTHS, 1932-33 



317 




FIG. ISO-ISOCHRONIC LINES FOR EXPECTATION IN DAYS BEFORE DAILY RANGE IN EXCEEDS lOOOr, 12 MONTHS, 1931-33 




FIG. I6I-IS0CHR0NIC LINES FOR EXPECTATION IN DAYS BEFORE DAILY RANGE IN Z EXCEEDS lOOOy, II MONTHS, 1032-33 



318 





* 


ao" 


220* 


2AO* 


iC41f (V GEOCRAPH 
2*0* 200' 


>c iqhgituocs 
joo* 


(DCAsr 
J20* 


MO' 





7* 


20* 


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ggj 






















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trito. 






i 








L "7 








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8 
1 


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5 

4 


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4 












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FIG. /fi£ — GEOGRAPHIC 4HD CEOMAQNETIC COORDINATE SYSTEMS FOR ENTIRE EARTH 
If OR tOTTOkt SCALE Of LONGiruOC. QUART -RfAD'HGS Of CEOMACNC Ttc LATtTuOE m AND lONGiTuOE (A) ARE SOUTH AND EAST 
FROM fgo' RfSPftrivEtr) 




FIG. 163 -LINES OF EQUAL GEOMAGNETIC LATITUDE 



319 




FIG.IB4.- DAILY MAXIMA AND MINIMA HORIZONTAL INTENSITY, SITKA, ALASKA, SEPTEMBER I, 1932 ', TO AUGUST 31, 1933 



320 




FIG.I6S-DAILY MAXIMA AND MINIMA DECLINATION, SITKA, ALASKA, SEPTEMBER 1,1932, TO AUGUST 31, 1933 



321 




FIG. 166-DAILY MAXIMA AND MINIMA VERTICAL INTENSITY, SlTHA, ALASKA, SEPTEMBER I, '932, TO AUGUST 31,1933 



322 



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-PROBABILITY THAT DAILY AND WEEKLY RANGES OF H, D, AND Z EXCEED VARIOUS MAGNITUDES, 12 

MONTHS, 1932-33 
DAILY RANGES WEEKLY RANGES 



323 



X ' ' 400 ' ' 800 ' ' 1200 ' 
\ SCALE IN GAMMAS 1 

\s HORIZONTAL INTENSITY 


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\. DECLINATION 
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FIG. 168(A) AND (B) -PROBABILITY THAT RANGES IN H, D, AND Z, DURING GIVEN TIME-INTERVALS, EXCEED VARIOUS 
MAGNITUDES; (A) TROMS'O, 1930-37, AND (B) SITKA, 1905-30 



324 





TWO-MONTHLY 



THREE-MONTHLY 



FOUR -MON THL Y 



SIX-MONTHLY 



(O) 



FIG. 168(C) AND (D) — PROBABILITY THAT RANGES IN H, D, AND Z, DURING GIVEN TIME-INTERVALS, EXCEED VARIOUS 
MAGNITUDES, (C) CHELTENHAM, 1905-30, AND (D) HONOLULU, 1905-30 



325 




FIG. 163 -ISOCHRONIC LINES FOR EXPECTATION IN 3-MONTH PERIODS BEFORE 3-MONTHLV RANGE IN H EXCEEDS 500Y 




FIG. 110— ISOCHRONIC LINES FOR EXPECTATION IN 3-MONTH PERIODS BEFORE 3-MONTHLY RANGE IN D EXCEEDS 5007 



326 




FIG. Ill -ISOCHRONIC LINES FOR EXPECTATION IN 3-MONTH PERIODS BEFORE 3-MONTHLY RANGE IN Z EXCEEDS 5007 




FIG. I1Z-IS0CHR0NIC LINES FOR EXPECTATION IN WEEKS BEFORE WEEKLY RANGE IN H EXCEEDS 1000 7 



327 




FIG. 173-ISOCHRONIC LINES FOR EXPECTATION IN WEEKS BEFORE WEEKLY RANGE IN D EXCEEDS 1000? 




FIQ. 174- -ISOCHRONIC LINES FOR EXPECTATION IN WEEKS BEFORE WEEKLY RANGE IN Z EXCEEDS lOOOt 



328 




FIB. I7S—IS0CHR0NIC LINES FOR EXPECTATION IN MONTHS BEFORE MONTHLY RANGE IN H EXCEEDS lOOOf 




FIG. ITS -ISOCHRONIC LINES FOR EXPECTATION IN MONTHS BEFORE MONTHLY RANGE IN D EXCEEDS lOOOy 



329 




FIG. I77—/SOCHRONIC LINES FOR EXPECTATION IN MONTHS BEFORE MONTHLY RANGE IN Z EXCEEDS lOOOy 




FIG. na-ISOCHRONIC LINES FOR EXPECTATION IN 3-MONTH PERIODS BEFORE 3-MONTHLY RANGE IN H EXCEEDS lOOOf 



330 




fki.its-isochronic lines for expectation in 3-month periods before 3-monthly range in d exceeds looor 




Fia.lBO — ISOCHRONIC LINES FOR EXPECTATION IN 3-MONTH PERIODS BEFORE 3-MONTHLY RANGE IN Z EXCEEDS I0OOT 



331 




FIG.I&I-ISOCHRONIC LINES FOR EXPECTATION IN 6-MONTH PERIODS BEFORE 6-MONTHLY RANGE IN H EXCEEDS lOOOr 




F/G.I81-IS0CHR0NIC LINES FOR EXPECTATION IN 6-MONTH PERIODS BEFORE 6-MONTHLY RANGE IN D EXCEEDS lOOOy 



332 




FIGJ83-ISOCHRONIC LINES FOR EXPECTATION IN 6-MONTH PERIODS BEFORE 6-MONTHLY RANGE IN Z EXCEEDS lOOOr 




FIC.I6A--IS0CHR0NIC LINES FOR EXPECTATION IN YEARS BEFORE YEARLY RANGE IN H EXCEEDS 1000 r 



333 




fib. les -isochronic lines for expectation in years before yearly range in d exceeds 10007 




FIS. IBS -ISOCHRONIC LINES FOR EXPECTATION IN YEARS BEFORE YEARLY RANGE IN Z EXCEEDS 10007 



334 




F/S. 187 -ISOCHRONIC LINES FOR EXPECTATION IN 3-MONTH PERIODS BEFORE 3-MONTHLY RANGE IN H EXCEEDS ISOOy 







FlS. 138- ISOCHRONIC LINES FOR EXPECTATION IN 3-MONTH PERIODS BEFORE 3-MONTHLV RANGE IN D EXCEEDS ISOOf 



335 




-BELTS (BOUNDARIES SHOWN BY BROKEN LINES) NEAR EACH AURORAL ZONE IN WHICH AVERAGE PROBABILITY IS AT LEAST 0.1 
THAT TOTAL 3-MONTHLY RANGE IN H EQUALS OR EXCEEDS IOOOT 




K k \\ \ L 



FIO ISO —BELTS (BOUNDARIES SHOWN BY BROKEN LINES) NEAR EACH AURORAL ZONE IN WHICH AVERAGE PROBABILITY IS AT LEAST 0.1 
THAT TOTAL 3-MONTHLY RANGE IN D EQUALS OR EXCEEDS lOOOy 



336 




FIG 13!- BELTS (BOUNDARIES 



SHOWN BY BROKEN LINES) NEAR 
THAT TOTAL 3- MONTHLY 



EACH AURORAL ZONE IN WHICH AVERAGE PROBABILITY IS AT LEAST 
RANGE IN Z EQUALS OR EXCEEDS lOOOr 




337 



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339 




F/B 197 —VARIATION WITH LATITUDE OF FREQUENCIES OF FLUCTUATIONS OF VARIOUS DURATIONS, 10 

TO 500 SECONDS, H, D, AND Z, MEAN OF SIX DAYS, MAY 9 (C^O.O), JULY 4 (C-0.4) , MAY 5 (C = O.B), 

MAY 31 (C-1.2), MARCH 24 (C = l.lJ, AND MAY I (C = l.9), 1933 



340 




FICISi-VARIATION WITH GEOMAGNETIC LATITUDE OF MAGNITUDE Or TOTAL IMPULSE, AS 

measured By i/i z&rat, with 6f the amplitude and at the duration, fop fluctuations 

OF DURATION 10 TO SOO SECONDS FOP DAYS OF VARIOUS MAGNETIC CHARACTER-FIGURES C 



341 




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FIG. 201- VARIATION WITH GEOMAGNETIC LATITUDE IN HOURLY FREQUENCY OF POSITIVE AND NEGATIVE FLUCTUAT IONS, DURATIONS 
10 TO 500 SECONDS, H, D, AND Z , MEAN OF SIX DAYS, MAY 9 (C'O.O), JULY 4 (C-0.4), MAY 5 (C=O.S), MAY 31 (C-I.Z), MARCH Z4 
(C-I.S), MAY I (C=l.9), 1933; • = POSITIVE FLUCTUATION, < = NEGATIVE FLUCTUATION 



343 



S0N033S-rH*rD HI 3S7l)d*l JO 31¥DS rs 




FIG 2.03 -ISOMAONETIC LINES FOR AMPLITUDE OF FLUCTUATIONS IN H, TO 150 SECONDS DURATION, WITH AVERAGE PROBABILITY 

FOR 3-MONTH INTERVALS 



344 




FlG.iO* - ISOMAGNET IC LINES FOR AMPLITUDE OF FLUCTUATIONS IN O, TO ISO SECONDS DURATION, WITH AVERAGE PROBABILITY OF 0.1 

FOR 3-MONTH INTERVALS 




FIG. ZOS- ISOMAGNET IC LINES FOR AMPLITUDE OF FLUCTUATIONS IN Z, TO ISO SECONDS DURATION, WITH AVERAGE PROBABILITY OF 0.1 

FOR 3-MONTH INTERVALS 



345 




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I0 h 20 m GMT, MARCH 9, 1933 
(duration 10 MINUTES) 




FlG.ZQQ-LATITUDE-OlSTRIBUTIONS OF MAXIMUM DISTURBANCE-VECTORS FOR SMALL FLUCTUATIONS; 
VIEW FROM ABOVE GEOMAGNETIC NORTH POLE 

(southern-latitude stations shown in corresponding northern latitudes with east and VERTICAL 

COMPONENTS REVERSED IN SIGN J 
LEGEND AS IN FIGURE Z06 



DECLINATION 



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FIG.2I0-GEOMAGNET/C EFFECTS LIGHTNING-DISCHARGES, HUANCAYO f PERU 

(VERTICAL TIME-MARKS AT FIVE-MINUTE INTERVALS WITH ONE~MINUTE 

INTERVALS AT HOUR) 



349 





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FIG. ZI9- SIMULTANEOUS FLUXMETER RECORDS ON MAGNETICALLY QUIET DAY; (A) COLLEGE, ALASKA, AND (B) CHELTENHAM, MARYLAND, APRIL 8, 1943 



I0 h 00" 



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GREENWICH 


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FIG.IZO- SIMULTANEOUS FLUXMETER RECORDS ON MODERATELY DISTURBED DAY; (A) COLLEGE , ALASKA, AND (B) CHELTENHAM, MARYLAND, APRIL 10,1943 



353 



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(B) 



FIG.Z2I-SIMULTANE0US FLUXMETER RECORDS ON MAGNETICALLY DISTURBED DAY; (A) COLLEGE, ALASKA, AND (B) CHELTENHAM, MARYLAND. FEBRUARY 17, 1943 



lasts'" is h 30" 

GREENWICH MEAN TIME 



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ia h 4s" 



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VERTICAL INTENSITY 



I3 h 30" 
GREENWICH MEAN TIME 



(8) 



FIG.Zlt-FLUXMETER RECORDS OF UNUSUAL CHARACTER SHOWING (A) DAMPED SINUSOIDAL WAVES OF PERIOD ABOUT TWO MINUTES, NOVEMBER 23, 1942, 
AND (B) LARGE SHORT-PERIOD OSCILLATIONS OF UNUSUALLY SHORT DURATIONS, NOVEMBER 24, 1942, COLLEGE, ALASKA 



354 





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355 



CHAPTER X 



MAGNETIC STORMS AND ASSOCIATED PHENOMENA 



1. Introduction . --Birkeland [29] has studied world- 
wide features of geomagnetic disturbance for individual 
magnetic storms. In a number of memoirs Chapman [62, 
63,64] made important extensions of these investigations, 
using more extensive data involving field-characteristics 
averaged for many storms. As a result of these studies, 
he proposed an electric current system of storms in 
which the polar parts at least flowed in the atmosphere. 
In a subsequent paper, Vestine and Chapman [37] showed 
that this current system was in good general agreement 
with the average characteristics derived from data for 
the Polar Year, 1932-33. It was concluded that the mag- 
netic data were compatible with the simple form of cur- 
rent system, in which at least the circuits of the intense 
polar current circulation were closed in the atmosphere. 
It was estimated that these currents flowed at a height 
100 to 150 km above the Earth, for the region near the 
auroral zone, in good agreement with other estimates by 
McNish [65]. It was further concluded that the polar cur- 
rent system suggested by Birkeland, in which the current 
circuits were not closed in the atmosphere, was incon- 
sistent with observation in several important respects. 

In the present investigation, the current system pro- 
posed by Chapman is examined to check its agreement 
with observation for individual hours of magnetic storm; 
the present study thus supplements the previous discus- 
sion based on the average characteristics of storms. The 
possibility that a part of the current may flow in the form 
of an equatorial ring [66] at a distance of a few earth- 
radii is not considered. The comparisons are effected 
through independent derivations of the currents required 
in the atmosphere for selected hours of four magnetic 
storms, using rough tentative corrections for induced 
earth currents. The derivations are made for the case 
of the real rather than an ideal Earth previously con- 
sidered by Chapman. 

A knowledge of the storm-field alone at the Earth's 
surface does not enable us to determine the form and po- 
sition of the external electric current system responsible. 
The space distribution of electrical conductivity suggests 
that this current system may flow in the atmosphere. 
Added support for this view will result if it is found that 
this atmospheric current system appears simpler than 
other possible systems calculated from the storm -field 
alone, for regions in space more distant from the Earth. 

2. The electric current system. --Let us first con- 
sider the current system derived by Chapman for the 
average of 40 moderate magnetic storms and other sup- 
plementary averaged characteristics of the observed 
field. The current system is shown in A of Figure 227 
where it is drawn appropriate to a spherical Earth hav- 
ing its geographic and magnetic axes coincident. It is 
intended to correspond, apart from irregular disturb- 
ances, with the geomagnetic variations (or disturbance 

D) of the Earth's field additional to those present on mag- 
netically quiet days. 

On the left-hand side is shown a view from the Sun 
for a time of magnetic storm (main phase). On the right 
a view from above the north pole is represented. The 



current system is thus suppos 1 fixed in orientation 
relative to the Sun, and the Earth revolves within it. 
A total of 10,000 amperes flows between successive 
current lines. The currents are most concentrated 
along the zones of maximum auroral frequency. 

The current system may be analyzed into two partial 
systems shown in B and C of Figure 227. B of Figure 
227 represents that responsible for the storm-time 
component (D s t) of disturbance (it is the nonpolar part 
of this system that is not definitely assigned to the 
Earth's atmosphere); C of Figure 227 shows the part 
responsible for the disturbance daily variation (Sd) de- 
pending mainly on local magnetic time. 

The current system is given an idealized pattern and 
alters markedly in intensity, and to some extent also in 
form and sign, with the time. This then is the current 
system (and its parts) derived from consideration of the 
average fields of storms, and which we seek to compare 
with corresponding systems appropriate to individual 
hours of storm. We will first consider the characteris- 
tics of the mean hourly disturbance field of polar regions 
for various selected hours of disturbance. 

3. The polar field of magnetic storms. --The storms 
of October 14 and December 14, 1932, and of April 30 and 
August 5, 1933, were selected for study, being four of the 
most intense storms of the Polar Year, 1932-33--a year 
near the sunspot minimum. These do not include an ex- 
ample of a very great magnetic storm. 

Mean hourly disturbance vectors were derived for 
about 30 hours of each storm, for about 25 stations in 
magnetic latitudes north of 55°. At a few stations, datp 
for the whole or part of the storm were sometimes miss- 
ing for various reasons, one important reason being the 
use of instruments not sufficiently insensitive. The dis- 
turbance was measured as the departure from the mean 
of an international quiet day near the day of storm. The 
quiet days used were (where possible) those of October 
14 and December 12, 1932, and May 12 and August 1, 1933, 
the same for all stations. The disturbance vectors were 
derived from published or other tables of mean hourly 
values of magnetic force or, in a few cases, from micro- 
film reproductions of magnetograms. It is thought that 
inaccuracies of measurement seldom exceeded 25 y for 
the polar stations of the Union of Soviet Socialist Repub- 
lics and Jan Mayen for which the microfilms were used. 

The disturbance vectors so derived were plotted on 
maps of the north polar regions, for each of the 30 hours 
of each storm. Of these, a number have been selected 
for reproduction here; those for the storm of April 30 
and May 1, 1933, and others thought to be fairly typical 
for the remaining three storms (or of special interest) 
were selected. 

Figures 228 and 229 show the geographical distribu- 
tion of the disturbance vectors at polar stations in rela- 
tion to the position of the Sun. Geomagnetic co-ordinates 
of position are used and the dotted curve represents the 
average position of the auroral zone as estimated from 
magnetic data for disturbed days of the Polar Year [38]. 
A and B of Figure 228 are for the hour of maximum of 



357 



358 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



the initial phase of the storms of October 14, 1932, and 
April 30, 1933, respectively. For these two special 
cases, only the disturbance vectors at each station are 
measured as the departures from the mean hourly values 
of the force found for the hours ending at 16h and 17h 
GMT, respectively, just before the commencements of 
the storms. 

The data of A of Figure 228 suggest the presence of 
D s t in the form of electric currents external to the 
Earth flowing from west to east and nearly symmetrical 
about the Earth's magnetic axis. There is also a sug- 
gestion that there may be a current circulation, anti- 
clockwise as seen from above the Earth, centered some- 
what south of the auroral zone and near a magnetic lon- 
gitude of 270° E. It is noteworthy that the disturbance 
vectors are relatively small and in general very little 
larger in magnitude in polar than in low latitudes. 

B of Figure 228, drawn for the maximum of the ini- 
tial phase of the storm of April 30, 1933, shows marked- 
ly different characteristics from those of A, in high lat- 
itudes. A possible explanation may be that a consider- 
able amount of irregular disturbance has appeared in 
polar regions in the case of B (note the change in the 
scale of force). In lower latitudes, as in the case of A, 
there is some evidence of a symmetrical storm -time 
part consisting of a current flowing from west to east. 

C to F of Figure 228 and A to F of Figure 229 re- 
late to the main phase of magnetic storms. The appro- 
priate scale of force is given at the bottom of the page, 
except in certain cases where it is shown on the particu- 
lar map to which it refers. 

For the main phase of each storm, the changes with 
time in the polar disturbance field depend in a marked 
way upon the position of the Sun. This is very clearly in 
evidence near the center of the auroral zone where the 
horizontal component of disturbance is relatively large 
and persistent and in a direction tending to be nearly 
perpendicular to the meridian plane including the Sun. 
Near the auroral zone, the disturbance is most intense 
and highly differentiated locally. The polar disturbance 
field inside the auroral zone usually, and perhaps always, 
consists of two areas in which the vertical components 
are opposite in sense. This is # in good agreement with 
the previous findings of Birkeland, but the intense hori- 
zontal disturbance near the center of the auroral zone is 
different from the characteristics ascribed by him to 
this region on the basis of his more scanty data. 

Progressing southwards from the center of the au- 
roral zone, the north component tends to reverse in sign 
near the center of the region between the pole and the 
auroral zone, attains a marked maximum change near 
the auroral zone, and again reverses sign just outside 
the auroral zone. 

The eastward component of the horizontal force in- 
side the auroral zone tends to be large and positive near 
local noon, large and negative in the evening, and reverses 
near the auroral zone, becoming relatively small in low- 
er latitudes. 

The vertical component tends to be relatively small 
near the center of the auroral zone. With decreasing 
latitude, it attains a considerable magnitude just inside 
the auroral zone and reverses sign near the zone. It 
again becomes large and opposite in sense just outside 
the auroral zone, after which it rapidly decreases in 
magnitude. The disturbance in the vertical component 
is largest for times near local dawn and evening, and 
smallest near noon and midnight. 



The polar disturbance field for individual hours of 
storm shows distinct evidence of important systematic 
changes with time. In general, these closely resemble 
those found from the average characteristics of the field, 
although there may be considerable variability from hour 
to hour during an individual storm. 

There is also evidence to suggest the presence of 
important seasonal change in the character of the polar 
disturbance field. For the storm of December 15, 1932, 
there is very little indication of eastward-flowing elec- 
tric currents along and above the auroral zone, although 
those flowing westward apparently attain considerable 
intensities. It appears probable that near the times of 
equinox and summer the eastward currents are more 
nearly comparable in magnitude with the westward cur- 
rents, though perhaps always weaker in magnitude. 

E of Figure 228 shows that the storm-field may ap- 
pear relatively simple when the disturbance shows its 
maximum general development in intensity. 

The disturbances recorded at stations near the au- 
roral zone are particularly complicated because of the 
rotation and lateral displacement with time of a highly 
differentiated disturbance field. It may also be men- 
tioned that rapid, oscillatory changes in the force are 
most marked in this region, perhaps especially during 
the early morning hours. 

4. The electric current systems for individual hours 
of storm. --Whatever the form of the disturbance field at 
the Earth's surface, this field could be reproduced by 
electric currents flowing as a thin, nearly spherical 
current sheet within the atmosphere. Even if this cur- 
rent system does not closely resemble the actual one, it 
affords a simple means of representation of the observed 
features of storms. It can also be used to derive the real 
current system, if this should be of a different type, with 
the aid of sufficient additional information concerning 
other nonmagnetic considerations. 

The atmospheric-electric current systems flowing in 
a spherical shell at a given height can be derived from 
the observed surface field of disturbance, using the meth- 
ods of general potential theory. These methods require 
a knowledge of the magnetic potential (or field) of the cur- 
rents for points everywhere on the Earth, but may give 
satisfactory results provided sufficient accuracy is at- 
tainable by interpolation of values between points at which 
the field is measured. It would obviously be difficult to 
effect a formal interpolation of the data of Figures 228 
and 229. It therefore appears useful to estimate the form 
and intensity of the current systems approximately at 
first, using speedy but simple methods similar to those 
used previously by Chapman and Vestine [37]. These 
methods involve a knowledge of the fields due to simple 
model current systems, and the assumption that the cur- 
rent circuits are closed in the atmosphere. Before mak- 
ing such estimates, it is desirable to obtain a rough in- 
dication of the magnitude of that part of the observed 
surface field which is of external origin, and we will now 
consider correction of the data for induced earth currents. 

The corrections here applied are rough and only ten- 
tative. We have seen that the main systematic features 
of the polar disturbance field of storms just discussed 
show considerable resemblance to those deduced from 
average characteristics. It thus appears likely that cor- 
rections for induced currents estimated for the average 
field may afford a rough but useful approximation to 
those required in the case of mean hourly disturbance 
during storms. The effects of induced currents are 



MAGNETIC STORMS AND ASSOCIATED PHENOMENA 



359 



likely, in general, to augment the horizontal components 
and decrease the vertical components of origin external 
to the Earth. A study of this kind gave a rough approxi- 
mation for the required correction, in the case of the 
average polar characteristics of storms, using consid- 
erations of general potential theory. In this analysis, 
the polar cap of the Earth was supposed plane. This 
study suggested that the observed horizontal components 
should be multiplied by factors estimated to be roughly 
0.9 near the center of the auroral zone, 0.7 near the 
boundary of the zone, and decreasing to about 0.6 outside 
the zone, in obtaining the contribution of external origin. 
Corresponding ratios were adopted for the vertical com- 
ponents, the corrections in these cases resulting in in- 
creasing the observed magnitudes. These values were 
then interpolated linearly with distance, measured from 
the center of the auroral zone, and applied to the mean 
hourly disturbance vectors of storms. The number of 
stations used for Figures 228 and 229 was increased to 
45 by the addition of data for low latitudes. 

Figures 230 to 235 show to scale the disturbance 
vectors and their geomagnetic distribution after apply- 
ing the foregoing rough corrections for induced currents. 
The representation is for the Northern Hemisphere as 
viewed from directly above the geomagnetic north pole. 
The disturbance vectors for stations in low latitudes of 
the Southern Hemisphere have been assumed approxi- 
mately the same as for stations in the same geomagnetic 
latitude and longitude in the Northern Hemisphere, ex- 
cept for reversal of direction in the eastward and verti- 
cal geomagnetic components of force. Except in A of 
Figure 230, the scale of force is five times as open in 
lower latitudes (stations south of a magnetic latitude $ = 
60°) as in polar regions. The average position of the au- 
roral zone estimated from magnetic data for interna- 
tional disturbed days of the Polar Year, 1932-33, is 
shown by a broken line [38]. The approximate direction 
to the Sun is indicated by an arrow drawn outwards (ver- 
tically downwards in the diagrams) from the geomagnetic 
north pole. The disturbance vectors at stations south of 
$ = 55° have been corrected for the quiet-day daily vari- 
ation given by the mean of the five international quiet 
days of the month. 

Also shown in the figures are the corresponding elec- 
tric current systems estimated from the data. The esti- 
mates of current above the neighborhood of a station 
were made by approximate methods. For instance, near 
station 38 of A of Figure 230, the field is nearly uniform 
and could be caused by electric currents flowing approx- 
imately from west to east above the Earth. The field in 
this region will be less affected by currents flowing at 
greater distances from the station than by currents im- 
mediately above the station. The field near the station 
resembles fairly closely that of a complete spherical 
current sheet, in which the current varies only as the 
cosine of the latitude. Using simple graphs giving the 
distance between successive current lines for a flow of 
10,000 amperes, in terms of the observed horizontal 
component of force, we obtain approximate estimates of 
the current near an individual station. 

In regions where the currentf low extends over shorter 
distances without abrupt change in direction, estimates 
were obtained using the known fields of infinite uniform 
plane current sheets or uniform ribbon currents. In gen- 
eral, there was good qualitative agreement between the 
currents derivedf rom the horizontal components and the 
observed signs and magnitudes of the vertical components. 



The spacings between successive current lines and 
directions of flow were estimated for a restricted re- 
gion above each station in turn. The current lines were 
then connected and shifted slightly, where necessary, so 
that the current circuits were closed. In regions where 
data were not available, the spacing of the current lines 
is of course uncertain and some liberties have been tak- 
en in drawing such lines; in certain cases it was sup- 
posed that some degree of symmetry was required rela- 
tive to current lines more accurately determined for ad- 
jacent regions, subject to the condition of continuity of 
current flow. 

In the foregoing manner there was estimated to be a 
total of 130,000 amperes in the large circuit involving 
anticlockwise flow of current, and about 15,000 amperes 
in the small opposed equatorial current circulation. So 
far as the writer is aware, this procedure, though simple, 
has not previously been applied in the study of the initial 
and main phase of individual magnetic storms. 

A of Figure 230 shows the current system estimated 
for the maximum of the initial phase of the storm with 
sudden commencement at 17h 47m, October 14, 1932. 
A total of 10,000 amperes flows between the successive 
current lines. The disturbance in polar regions is of 
the same order of magnitude as in lower latitudes. The 
currents from the equator and northwards circulate from 
west to east about a center slightly south of Fort Rae. 
Except in the region north of Fort Rae, there has been 
an initial increase in the northward component of force -- 
a well-known characteristic of the initial phase of mag- 
netic storms. 

There are striking differences between the current 
system in A of Figure 230 for the initial phase and the 
current system in A of Figure 227 for the main phase of 
storms. If A of Figure 230 be analyzed into its sym- 
metrical (D s t) and antisymmetrical (Sd) parts, the 
storm-time currents in low latitudes would flow from 
west to east instead of from east to west as in the main 
phase. The SD-part would resemble that of C of Figure 
227 in general type, but the polar circuits would be much 
weaker relative to the lower-latitude circuits than for 
the case of the main phase. In the present case, there 
is also some possibility that the Sp- and D s t-parts in 
lower latitudes are somewhat distorted due to incomplete 
removal of the effect of the quiet-day daily variation, 
since the magnitude of the disturbance is relatively small. 

B of Figure 230 shows the current system derived for 
the maximum of the initial phase for the storm with sud- 
den commencement at 16h 27m, April 30, 1933. In low 
latitudes the characteristics show considerable resem- 
blance in general type with A of Figure 230, though of 
greater intensity. In polar regions, for which the dis- 
turbance vectors are here drawn to a scale one -fifth as 
open as for lower latitudes, there is marked disturbance 
in the region near and within the auroral zone. However, 
there appears to be some possibility that a considerable 
part of the polar disturbance, as well as that in lower 
latitudes, was occasioned by the superposition of the 
field of a magnetic bay upon the general storm-field. 
The intensity of the polar current circulation was esti- 
mated on the basis of approximate methods used pre- 
viously by Vestine and Chapman [37], on the assumption 
that the current circuits are completed in the atmos- 
phere. 

A of Figure 231, for the main phase of storms, has 
been included because of the rather special features 
shown. In this case, the disturbance near the center of 



360 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



the auroral zone is more marked than elsewhere. During 
the 17 -hour interval following the commencement time 
for B of Figure 230, there was but little magnetic dis- 
turbance in polar regions. The disturbance at stations 
one and two gradually increased for several hours to at- 
tain a maximum value (for station one) at llh, May 1, as 
shown in A of Figure 231. This characteristic was not 
found in the other three storms studied, and the marked 
disturbance in the vertical component appears a matter 
of particular interest. In the storm of May 1, it was 
first clearly present at 7h, increased to maximum in- 
tensity near llh, after which a transition to conditions 
at 14h (B of Figure 231) gradually took place. There 
appears to be evidence for a relatively intense current 
circulation near the center of the auroral zone, but there 
are insufficient data to trace out the form of current flow 
with much degree of certainty. 

In lower latitudes, it would appear that the variation 
D s t is produced by current circulations weaker than 
those for Srj (A of Figure 231), and the situation thus is 
different from the case of A of Figure 227, where the 
opposite tendency is shown. We shall later discuss the 
fact that A of Figure 227 appears to correspond more 
closely with conditions operative near the maximum of 
the main phase of storms; in the present storm the max- 
imum appears about six hours later. 

In B of Figure 231, the field-changes appear more 
intense than in the case of A. The current sheet flowing 
across the polar cap tending in a direction towards the 
Sun, if nearly uniform, is estimated to have an intensity 
of 1,900,000 amperes. This estimate was found to agree 
fairly well also with independent estimates of the intense 
currents returning along the auroral zone, on the basis 
of the approximation of an infinite linear auroral zone 
current for stations some distance outside the zone, or 
on the assumption of an infinite plane ribbon current for 
stations very near or at the zone. 

In low latitudes, the currents are somewhat symmet- 
rically arranged relative to the Sun, and the current den- 
sity is less on the morning than on the evening side of 
the Earth. 

In the sequence B of Figure 231 to A of Figure 234, 
the main phase of the storm is well developed, attaining 
its maximum intensity near 16h, May 1, when a total of 
2,000,000 amperes flows in the interzonal sheet current 
across the polar cap of the Earth. The estimates of the 
width in latitude of the auroral zone currents, made on 
a ribbon current hypothesis, are very rough and only 
tentative. 

A of Figure 234 shows the storm-field considerably 
reduced in intensity and the eastward flow of current ap- 
pears relatively much weaker than the westward flow 
along the zone. In this storm it would thus appear that 
D s t is relatively greater in intensity with respect to Sd 
during the phase of recovery than during the maximum of 
the main phase. 

B of Figure 234, and A and B of Figure 235, for the 
main phase of other storms, show characteristics simi- 
lar in general type to those for the storm of May 1, 1933. 
In the case of the storm of December 15, 1932, the only 
hour of the storm in which evidence was found of eastward 
flowing currents along the auroral zone was on Decem- 
ber 15, shown in A of Figure 235. This may result from 
a seasonal effect and suggests that D s t is relatively 
more intense with respect to Sd in winter than it is in 
summer. 



The current systems derived for the main phase of 
storms show good general agreement in type with A of 
Figure 227, proposed by Chapman, apart from differ- 
ences in intensity. There are a few minor differences 
apparent in the current systems here derived for the 
case of the real Earth. In most cases, the polar current 
system as seen from above shows a greater amount of 
clockwise rotation relative to the position of the Sun than 
in the case of A of Figure 227. In their expansion with 
increasing intensity of storm, the auroral zone currents 
seem also to show considerable symmetry relative to 
the average position of the auroral zone, which in the 
case of the real Earth is of course not circular. 

A and B of Figure 236 show the results of analyzing 
A of Figure 232 into its symmetrical (D s t) and antisym- 
metrical (Sd) parts. This separation was effected by 
averaging the current in A of Figure 232 along parallels 
of latitude; in the case of the polar part the intensity of 
the current was averaged along the path of the auroral 
zone current. The magnitude of the symmetrical part 
within the auroral zone could not be estimated with ac- 
curacy, due to the scanty magnetic data, but the indica- 
tions clearly suggest that the storm-time currents in 
this region are relatively much smaller than in B of 
Figure 227. 

The following table gives a comparison of the results 
of Figure 236 with those found by Chapman for the aver- 
age of 40 storms, given in Figure 227. Thus, by multi- 
plying the estimates given by Chapman by about four, we 
obtain rather good agreement with the corresponding 
current estimates found here for the currents during an 
individual hour of storm. This suggests that the mag- 
netic storm of May 1, 1933, was about four times as in- 
tense as the average of the 40 magnetic storms consid- 
ered by Chapman. Chapman also estimates that the great 
magnetic storm of May 15, 1921, was about 15 times as 
intense as the average for the 40 magnetic storms [64]; 
this great magnetic storm was therefore probably asso- 
ciated with electric currents (if flowing in the same re- 
gion above the Earth) about four times as intense as 
those for the magnetic storm of May 1, 1933. 

Comparison of current-intensities in amperes for 16h, 

May 1, 1933 (A), with corresponding values 

averaged for 40 storms (B) 





Dst 


Region 


(A) 


(B) 


Lower latitudes 

High latitudes 
(auroral zone) 


700,000 
300,000 




200,000 
75,000 






s D 


Region 


(A) 


(B) 




Morning 


Evening 


Morning 


Evening 



Lower latitudes 250,000 200,000 50,000 50,000 

High latitudes 
( auroral zone) 1,000,000 1,000,000 275,000 275,000 

Figure 237 shows the result of an analysis for the 
initial phase of the storm of October 14, 1932. In the 



MAGNETIC STORMS AND ASSOCIATED PHENOMENA 



361 



case of both D s t and Sd, the electric currents estimated 
are much weaker than those for the main phase, as can 
be seen from an inspection of B of Figure 235 for the 
same storm. The most interesting feature is that the 
polar part of the Sd current system, as it appears in the 
main phase, seems to be missing, the parts ordinarily 
flowing in lower latitudes apparently extending directly 
over the polar cap. The symmetrical part also flows in 
the opposite direction to that for the main phase. 

5. Electric current system of magnetic bays. - -W ith 
the use of three -hour disturbance vectors from data of 
the Polar Year, 1932-33 [29], an estimate of the average 
electric current system of bays was attempted. This cur- 
rent system is shown plotted for OOh GMT in Figure 238, 
as derived using the method due to Chapman [64]. The 
average horizontal disturbance at each station is indi- 
cated by an arrow drawn from the station as origin; the 
vertical component is indicated by a line with bar --posi- 
tive when in the direction of the geomagnetic north pole. 
It was assumed tentatively that a correction given by 0.6 
times the observed horizontal disturbance removed the 
influence of induced earth currents. A correction was 
also applied to obtain the corresponding increase in the 
vertical component. The vectors preceding and following 
the average vector for OOh GMT by intervals of three 
hours were also plotted by rotating position of the station 
through a roughly approximate angular displacement about 
the geomagnetic axis. With the use of small current-sys- 
tem models and with the current assumed to flow on the 
surface of a spherical shell 150 km above the Earth, the 
approximate current system of Figure 238 was obtained. 
A total of 50,000 amperes flows between successive cur- 
rent lines in the figure. 

The interzonal current sheet flowing across the polar 
cap has an intensity of 600,000 amperes which divides so 
that 100,000 amperes flows eastward along the auroral 
zone and 500,000 amperes westward in this closed polar 
current circuit. The currents flowing along the auroral 
zone are augmented by additional contributions from the 
two low -latitude current circulations so that in the most 
concentrated portions about 150,000 amperes flow east- 
ward and about 600,000 amperes westward. 

The current system resembles that of the diurnally 
varying part of the Sd current system of magnetic 
storms. The storm-time part of the current system of 
storms is in evidence, as indicated by the greater inten- 
sity of westward than eastward flowing electric currents 
along the auroral zone. The current system remains 
fixed in average position relative to the Sun, the Earth 
rotating inside. Consequently, a point on the Earth's 
surface will experience a varying magnetic field corre- 
sponding somewhat to its proximity to the more concen- 
trated portions of the current circulation. In view of the 
fact that the current system here represented for the 
time of maximum of bays does not usually endure for 
more than one to five hours, the effect of the Earth's ro- 
tation may be a secondary factor determining the course 
of a bay . 

The greater number of negative bays as compared 
with positive bays selected in auroral regions can be at- 
tributed to the greater current intensity of the v/estward 
current as compared with the eastward currents flowing 
along the auroral zone; the number of positive and nega- 
tive bays should be the same but because of the selection 
rules adopted, which reject bays below a certain ampli- 
tude, the observed disparity results. In low and middle 
latitudes, a total of 250,000 amperes flows in the more 



intense circulation and 200,000 amperes in the less in- 
tense circulation. Hence in these latitudes, since the 
eastward currents are stronger than are the westward 
currents, the selected positive bays are more numerous 
than are the negative bays. In the region near the center 
of the auroral zone, as shown by Thule, it is clear that 
little dependence in frequency on local time would appear. 
These findings are in good general agreement with ob- 
servation. In another study of the current systems of 
several individual bays, the results showed good general 
agreement with the average current system derived here, 
though there was marked seasonal distortion in polar re- 
gions. 

6. Association of magnetic disturbance with ionospher- 
ic phenomena and cosmic ravs. --A rather direct associ- 
ation of magnetic bays with marked ionospheric absorp- 
tion in auroral regions has been found by Wells [67] for 
College, Alaska, an association suggested by previous 
observations at Tromso in 1932-33, studied by Appleton 
[68]. It was found by Wells that during each of 69 signif- 
icant bays, there occurred high absorption which pro- 
duced partial to complete radio blackouts (Figure 239), 
limited in time to the duration of the bay. However, it 
was noted that radio blackouts could appear also in the 
absence of a bay. 

The absorption effect is explained as due to intense 
ionization below the E-layer, caused by corpuscular 
radiation from the Sun. 

Another pronounced effect is the rapid increase in 
height of the maximum electron concentration of the F- 
layer during the main (intense) phase of great magnetic 
storms [69]. After an hour or so, the F-layer, which 
may have attained heights as much as 1000 km, returns 
to its more customary level of about 300 km. It is not 
yet clear how this effect should be interpreted. There 
is certainly migration and redistribution of electrons 
within the outer atmosphere, when there are present 
strong electric currents which produce the main phase 
of storms. 

In Chapter V we noted a purely sinusoidal part of the 
annual variation which arises as a disturbance feature. 
This sinusoidal variation has its counterpart in F2-re- 
gion ionization [70] and in average cosmic-ray intensity 
[71]. The amplitude of the sinusoidal variation appears 
symmetrical about the geomagnetic equator and approxi- 
mately in phase for the geomagnetic, ionospheric, and 
cosmic-ray changes, though the phase reverses on either 
side of the equator. These effects are not understood, 
but in view of a recent finding by Forbush [72] of an in- 
crease in cosmic-ray intensity preceding storms, it 
would be interesting to attempt an explanation on the 
basis of seasonal variation in high-energy radiation ac- 
companied by ionization of the atmosphere. 

Figure 240 shows three marked increases in cosmic 
rays during February and March, 1942, and July, 1946. 
These Forbush found beginning nearly simultaneously 
with solar flares or radio fade-outs. The effect was 
noted in high and middle latitudes, but not at the equator 
where the cosmic rays may have had insufficient energy 
to penetrate to ground level in the presence of the geo- 
magnetic field. This important observation has been 
interpreted as suggesting that charged particles of very 
high energy may have been emitted from the Sun to pro- 
duce increases in cosmic-ray intensity, with simultaneous 
emission of ultraviolet radiation yielding an augmentation 
of the solar magnetic daily variation. During the main 
phase of great magnetic storms, there are sometimes 



362 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



noted less marked decreases in cosmic -ray intensity 
[36,71,72], an effect likewise not yet understood, though 
it has been suggested that an equatorial ring current at a 
distance of a few earth-radii might cause cosmic rays to 
deviate from their customary statistical distribution in 
latitude. It is of interest to note that the charged parti- 
cles of energies suitable for exciting auroral lines appear 
in lower latitudes at times of great magnetic storms as 
shown by the well-known expansion equatorwards of the 
auroral zone [3]. 

7. Solar radiation responsible for magnetic disturb- 
ance and allied phenomena. - -The nature of the charged 
particles from the Sun which cause magnetic disturbances 
has not yet been established, but it has been shown by 
Chapman and Ferraro that emission from the Sun in any 
suitable quantity requires streams or clouds of particles 
to be nearly neutral electrostatically to a high degree of 
approximation [3]. Although an outburst of matter from 
the Sun initially must comprise many kinds of particles, 
charged and uncharged, the mutual repulsions between 
particles of like sign will ensure a nearly neutral stream 
aggregation after traversal over the great distance to the 
Earth. It is likewise natural to expect that these emitted 
particles will vary in energy, so that it may even be pos- 
sible that the components of a neutral stream may be dif- 
ferent in early phases of a storm as compared with later 
phases. Thus an initial part of a stream reaching the 
neighborhood of the Earth might sometimes consist of 
protons and electrons, and a later part mainly of ions, 
electrons, and neutral particles. However, initial in- 
crease of cosmic-ray intensity, in the special cases 
noted by Forbush, need not be attributed to neutral aggre- 
gations, since the energy of such particles is exceedingly 
high, and they might hence proceed in too narrow a beam 
to account for the effects observed. 

It may be that the ring configuration near the geomag- 
netic pole at llh, May 1, 1933, shown in A of Figure 231, 
is evidence for neutral stream constituents of protons and 
electrons, since the radius of the area in which currents 
appear is only a few degrees of latitude. This is unfortu- 
nately the only instance found throughout the Polar Year, 
1932-33, in the records for Thule near the geomagnetic 
pole. Since the auroral zone is usually about 20°-23° in 
radius, this may indicate that electrons and ions are the 
preponderant constituents of the solar streams that cause 
disturbance. 

8. Statistical fluctuations in stream density. -- A fea- 
ture to which it seems that insufficient attention has yet 
been drawn is that of the probable linear extent in space 
of clouds of particles comprising a solar stream. Al- 
though the average variations of magnetic field taken for 
many storms yields a function varying rather smoothly 
with time, the most predominant features are the large 
and numerous statistical departures from this average, 
especially in higher latitudes. 

It was previously noted (Chapter IX) that the great 
majority of short-period fluctuations endure for about 50 
seconds. If we then assume approximately one day to be 
the travel time from Sun to Earth, as suggested by studies 
of sunspots and storms, the velocity of the particles will 
be about 108 centimeter per second. A particular cloud 
hence may have a linear extent, measured along the aver- 
age stream lines, of 5 X 10 9 cm (50,000 km), or about 
four earth-diameters. The cross-section of such a cloud, 
at some considerable distance from the Earth, cannot be 
inferred from existing data. Figures 206 to 209 of Chap- 
ter DC suggest the arrival of particles in patches in au- 



roral regions under the guiding influence of the geomag- 
netic field [29,48]. They may introduce ionization and 
hence increased electric conductivity within these areas 
of penetration, which, in the presense of electromotive 
driving forces, yields intensification of current flow 
locally, with completion of the circuit on a world-wide 
scale. 

The rather strong preference for durations of about 
50 seconds is truly remarkable. A preferred linear ex- 
tent of about 50,000 km for an incoming cloud requires 
explanation. It would be interesting to search for solar 
phenomena predominantly of 50 seconds' duration, near 
active energetic sunspot groups, and likewise in terres- 
trial aurora. 

Gartlein [73] has recorded fluctuations of about 50 
seconds' duration in photoelectric recordings of auroral 
intensity, which might be explained by cloud distributions. 
However, the particles causing auroral fluctuations need 
not necessarily penetrate the atmosphere to levels in 
which the magnetic fluctuations are generated, and this 
explains the lack of detailed correspondence between 
magnetic and auroral fluctuations. 

Wells, Watts, and George [57] have recently detected 
effects of incoming aggregations of particles or clouds 
having ionization-densities of 2 to 4 X 105 electrons per 
cc with the aid of high-speed multif requency ionospheric 
recorders. These observations were made during the 
magnetic storm of March 25-27, 1946, near Washington, 
D.C., and hence in middle latitudes. (See A and B of 
Figure 241.) The principal effects of influx of clouds 
were: (1) sudden changes in F -layer ionization; (2) rapid 
changes in F -layer heights, indicating turbulence which 
is often progressive from great to low heights and from 
high to low frequencies; (3) rapid fluctuations of echoes 
at the lower frequencies with occasional temporary dis- 
appearance indicating high absorption. 

Paralleling the case of aurora, where greatest bright- 
ness is apt to be found at the lower limit of visible au- 
roral rays, there seems to be most intense ionization 
formed by incoming cloud particles at the lowest level of 
penetration. The particles seem to penetrate to F2- and 
Fl -layers during strong disturbance, but there was little 
evidence found for penetration to the E -layer or below. 

On the basis of Stbrmer's calculations for aurora, the 
colatitude ex. of particles arriving singly is given by sin 
<x = (2a/^)l/2 where a is the distance to the Earth's 
center, and l 2 = eM/mv; here e is the electronic charge 
of either sign, M the magnetic moment of the Earth, m 
the mass of the particle, and v its velocity. 

For the present observations, a = 40°, roughly, so 
that l becomes about 3 x 10 9 CGS. Since e/m for elec- 
trons, protons, and calcium atoms is, respectively, 
1.8 x 10 7 , 9.6 x 103, and 2.4 x 10 2 , the value 3 x 10 9 for 
& would presuppose very high velocities for these incom- 
ing particles, well in excess of 10^ cm/sec required to 
give a travel time of about one day from Sun to Earth. 
Hence, these particles with shallow penetration, which 
seem to be charged, since they may arrive either by night 
or by day, are likely to arrive near the Earth in neutral 
streams. Their apparent terminus of path after travers- 
ing only a small air-equivalent of path [3], if they arrive 
at vertical incidence, is compatible with velocities more 
nearly of the order of 10^ cm/sec or less. If we inter- 
pret the increase in ionization near the terminus of path 
as an indication of size of particles, the particles con- 
tributing most eff ectly to the observed effects are more 
likely to be ions or protons rather than electrons. 



MAGNETIC STORMS AND ASSOCIATED PHENOMENA 



363 



9. Rocket experiments. - -Many of the outstanding un- 
certainties with respect to magnetic storms and their 
associated phenomena seem likely to be removed in fu- 
ture years by means of direct measurements within the 
upper atmosphere. Thus we might expect cloud-chamber 
and other experiments on rocket flights to give indica- 
tion of the nature of corpuscular and wave -radiation 
from the Sun. There will no doubt also be radio-pulse 



observations at great heights yielding information on 
structure of the ionized regions within and beyond the 
atmosphere. Since the current sheets of the electric 
current systems of the atmosphere have fields discon- 
tinuous in the horizontal component or passing vertically 
through these current sheets, direct magnetic measure- 
ments may be expected to establish their true heights. 



FIGURES 227-241 



Figure Page 

227. Electric current system of geomagnetic disturbance 366 

228-229. Geographical distributions of mean hourly magnetic vectors, magnetic storms .... 367 

230-235. Mean hourly disturbance vectors and corresponding electric current systems for 

height 150 km for maximum of initial phase and main phase of magnetic storms 369 

236-237. Partial current systems D s t and Sd initial and main phase of magnetic storms . . . 372 

238. Mean three-hour disturbance vectors of magnetic bays 373 

239. High absorption at College, Alaska, during magnetic bays 373 

240. Three unusual increases in cosmic-ray intensity at Cheltenham, Maryland, during solar 
flares and radio fade-outs 374 

241. Six successive normal and six successive disturbed ionospheric 15-sec. records 374 



365 



VIEW FROM SUN 



VIEW TOWARDS NORTH POLE 




fia.Zll -(A) ELECTRIC CURRENT-SYSTEM OF GEOMAGNETIC DISTURBANCE, (B) AND (C) RESPECTIVELY, PAR- 
TIAL CURRENT-SYSTEMS D sr AND S COMPRISING (A) 



366 




FIG.228-GE0GRAPHICAL DISTRIBUTIONS OF MEAN HOURLY MAGNETIC VECTORS, MAGNETIC STORMS 

LEGEND 
HORIZONTAL FOfiCff ■ VERTICAL FORCE — — ■ {VERTICAL COMPONENT POSITIVE WHEN DRAWN OUTWARDS FROM GEOMAGNETIC NORTH POLE) 

AURORAL-ZONE CURVE 

STATIONS 
I THULE S eSKDALEMVIR 0. RUDE SKOV 13. BEAR ISLAND 17. FRANZ JOSEF LAND 21. FORT Ra£ ZS. SW/OER 

, GOOHAVN ft GREENWICH 10. LQvO 14. KANDALAMSCHA 16. DICKSON 22 MEANOOK 26. YAHOUTSK 

3 JULIANNEHAAB 7 LERWICK II. TROMS& IS. PETSAMO 19. POINT BARROW Z3. CHESTERFIELD INLET 27 SLOUTZK 

4 SCORESBY SUND * JAN MAYEN 12 SODANKYLA 16. MATOTCHttIN SHAR 20 SlTxA 24 ACINCOURT 23 SVEAGRUVAN 

SCALE OF FORCE IN GAMMAS FOR I4 h , I6 h , AND I8 h , MAY I 
| | SOO^ JOO O 



367 



■ 






-» 



If 




FIG. B2B -GEOGRAPHICAL DISTRIBUTIONS OF MEAN HOURLY MAGNETIC VECTORS, MAGNETIC STORMS 

LEGEND 

HORIZONTAL FORCE ► VERTICAL FORCE - - ■ (VERTICAL COMPONENT POSITIVE WHEN DRAWN OUTWARDS FROM GEOMAGNETIC NORTH POLE) 

AURORAL-ZONE CURVE 

STATIONS 
I. THULE 5 ESXQALEMI/IR 9. RUDE SKOV 13. BEAR ISLANO I?- FRANZ JOSEF LAND 2f. FORT RA€ 25 SWIDER 

Z GODHAVN 6. GREENWICH 10. LOVO 14. KANDALAKSCHA 18. DICKSON ZZ MEANOOK Z6 VAHOUTSK 

J. JU^tANNEHAAB ?. LERWICK II. TROMSO IS. PETSAMO 19. POINT BARROW 23. CHESTERFIELD INLET Z7 SLOuTZK 

4. SCQRESBy SuND 6. JAN MAYEN 12. SODANKYLA 16. MATOTCHKIN SHAR ZO SITKA 24. AGINCOURT Z8. SVEAGRUVAN 

SCALE OF FORCE IN GAMMAS 
t S00_ IQO Q 



368 



SCALE OF FORCE 



SCALES OF FORCE IN GAMMAS 




I9 h GMT, OCTOBER 14, 1932 



F!G.230~M£AN HOURLY DISTURBANCE-VECTORS AND CORRESPONDING ELECTRIC CURRENT-SYSTEMS FOR HEIGHT ISO KM FOR MAXIMUM OF INITIAL PHASE OF MAGNETIC STORMS; VIEW FROM ABOVE 

GEOMAGNETIC NORTH POLE 



HORIZONTAL FORCE - 



1 THULE 

2 GODHAVN 

3 JULIANNEHAAB 

4 SCORESBY SUND 

5 ESKDALEMUIR 



VERTICAL FORCE - 



6 GREENWICH 

7 LERWICK 

8 JAN MAY EN 

9 RUDE SKOV 

10 LOVO . 



LEGEND 

{VERTICAL COMPONENT POSITIVE WHEN DRAWN OUTWARDS FROM GEOMAGNETIC NORTH POLE) AVERAGE AURORAL ZONE STATIONS MISSING DATA 

(100000 AMPERES FLOWS BETWEEN SUCCESSIVE FULL-DRAWN CURRENT-LINES) 
STATIONS 

16 MATOTCHHIN SHAR 21 FORT RAE 26 YAKHOUTSK 31 KUYPt'Q 36 CHRISTCHURCH 

17 FRANZ JOSEF LAND 22 MEANOOK 27 SLOUTZK 32 WATHEROO 37 APIA 
fB DICKSON 23 CHESTERFIELD INLET 28 SVEAGRUVAN 33- LUKIAPANG 38 HONOLULU 

19 POINT BARROW 24 AGINCOURT 29 HELWAN 34 ANTIPOLO 39 TuCSON 

20 SITKA 25 SWiOER 30 ALIBAG 35 TOOLANGI 40 TEOLOrUCAN 



TROMSO 
2 SODANKYLA 
'3 BEAR ISLAND 

KANDALAKSCHA 
5 PETSAMO 



41 CHELTENHAM 

42 HUANCAYO 

43 SAN FERNANDO 

44 ELIZABETHVILLE 

45 COLLEGE FAIRBANKS 



SCALES OF FORCE IN GAMMAS 




FIG.23I-MEAN HOURLY DISTURBANCE-VECTORS AND CORRESPONDING ELECTRIC CURRENT- SYSTEMS FOR HEIGHT ISO KM FOR MAIN PHASE OF MAGNETIC STORMS; VIEW FROM ABOVE GEOMAGNETIC 

NORTH POLE (LEGEND AS IN FIGURE Z30) 



369 



SCALES OF FORCE IN GAMMAS 










flG.Z3l~MEAN HOURLY DISTURBANCE-VECTORS AND CORRESPONDING ELECTRIC CURRENT- SYSTEMS FOR HEIGHT ISO KM FOR MAIN PHASE OF MAGNETIC STORMS; VIEW FROM ABOVE GEOMAGNETIC 

NORTH POLE (LEGEND AS IN FIGURE Z30) 



SCALES OF FORCE IN GAMMAS 




F/6.23J-MEAN HOURLY DISTURBANCE-VECTORS AND CORRESPONDING ELECTRIC CURRENT- SYSTEMS FOR HEIGHT ISO KM FOR MAIN PHASE OF MAGNETIC STORMS; VIEW FROM ABOVE GEOMAGNETIC 

NORTH POLE (LEGEND AS IN FIGURE Z3Q) 



370 



scales or roftce in gammas 




to 

24 h GMT, MAY I, 1933 



FIG.i3A' — MEAN HOURLY DISTURBANCE-VECTORS AND CORRESPONDING ELECTRIC CURRENT-SYSTEMS FOR HEIGHT ISO KM FOR MAIN PHASE OF MAGNETIC STORMS, VIEW FROM ABOVE GEOMAGNETIC 

NORTH POLE (LEGEND AS IN FIGURE 2J0) 



SCALES OF FORCE IN GAMMAS 




/* GMT, DECEMBER 13, 1932 



FIG.Z3S-MEAN HOURLY DISTURBANCE-VECTORS AND CORRESPONDING ELECTRIC CURRENT-SYSTEMS FOR HEIGHT ISO KM FOR MAIN PHASE OF MAGNETIC STORMS, VIEW FROM ABOVE GEOMAGNETIC 

NORTH POLE (LEGEND AS IN FIGURE 21a) 



371 




— — = AVE RAGE AURORAL ZONE 



riQ. 2 3 Q- (a) AND (B), PARTIAL CURRENT-SYSTEMS, D^ AND Sp, RESPECTIVELY, MAIN PHASE OP STORM 
(100,000 AMPERES FLOWS BETWEEN SUCCESSIVE FULL-DRAWN CURRENT-LINES) 



19" GMT, OCTOBER 14, 1932 




-AVERAGE AURORAL ZONE 



PIS. ZJT - (A) AND (3), PARTIAL CURRENT- SYSTEMS, D S[ AND Sp, RESPECTIVELY, INITIAL PHASE OF STORM 
(lO.OOO AMPERES FLOWS BETWEEN SUCCESSIVE FULL-DRAWN CURRENT- LINES) 



• 372 




U3J.3H #3d llOAOHOm 3NO 3A09V $1381030 Nl 31¥3S 




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374 



CHAPTER XI 



PREDICTION OF GEOMAGNETIC FLUCTUATIONS 



1. General remarks. --In practical applications of 
geomagnetism, as in closely related problems of radio 
communications, increasingly valuable use is being made 
of prediction. Accordingly, this short discussion of fore- 
casting geomagnetic and allied geophysical conditions is 
included here. 

Geomagnetic fluctuations have been closely linked 
with solar phenomena such as sunspots. Indices related 
to the magnitudes of geomagnetic fluctuations have been 
devised which have been successfully related in a statis- 
tical sense to solar indices, such as sunspot number, 
over a considerable number of years. 

Since ionospheric and magnetic disturbances are as- 
sociated, it has been found convenient to make use of 
geomagnetic indices in forecasting radio communications 
conditions, in much the same way as in weather forecast- 
ing, and with a similar degree of success. These fore- 
casts from geomagnetic indices are facilitated by sup- 
plementary forecasts based on more or less continuous 
observations of solar phenomena, such as changes in 
size and activity of sunspots. 

2. Bases for prediction. — For convenience, we may 
distinguish two major bases for prediction of geomag- 
netic fluctuations which in fact are apt to be found inher- 
ent in all successful schemes of prediction. 

The first is that, given the past of a function (a geo- 
physical time-series of fluctuations) arising from un- 
specified causes, it is assumed that these causes are also 
operative in the future. Each cause may make an inde- 
pendent contribution to the time-series, in which case 
the prediction may be described as linear (by analogy 
with electrical network theory). If this linear independ- 
ence of causes does not exist, or does not exist to suf- 
ficiently good approximation, the problem of nonlinear 
prediction arises. In any event, since the causes are 
unspecified, the justification for choice of linear or non- 
linear prediction can perhaps be made on the basis of 
experience with predictions of a given time series. In 
the linear case, a formal treatment is possible directly 
[74]; in the nonlinear case, it may be possible to arrive 
at a complete formal basis by trial and error. 

The second basis for prediction involves knowledge 
of some or all of the actual causes or events with which 
the phenomena to be predicted are closely associated. 
Thus in geomagnetic predictions, appearance of large 
and active sunspots are usually followed by magnetic 
storms. It is known that solar and magnetic activity 
are on an average covariant, and plausible theories Jiave 
been devised to explain the influence of the solar changes 
on geomagnetism. There occur active, regionally re- 
stricted areas on the Sun in the form of sunspots, prom- 
inences, and coronal-emission regions which have been 
studied in relation to geomagnetic disturbances [3]. It 
is found that the number and intensity of magnetic dis- 
turbances are covariant with the 11 -year cycle of solar 
activity. Larger magnetic disturbances occur more fre- 
quently near sunspot maximum than near sunspot mini- 
mum. 

Magnetic activity is usually measured in terms of 
ranges in geomagnetic elements, per three-hour interval, 



say. It is found that such ranges tend to be reproduced 
in magnitude at intervals of 26 to 28 days. This yields 
a valuable basis for prediction, especially successful 
during the few years immediately preceding a sunspot 
minimum, and moderately successful in other years. 
This recurrence tendency is of course useful in predict- 
ing magnetically quiet as well as disturbed conditions. 

Large geomagnetic fluctuations are found associated 
with visible fluctuations in active solar areas, and es- 
pecially with those in areas near the center of the solar 
disc. The activity in some solar regions may persist 
for several solar rotations of about 27 days, permitting 
forecasts of geomagnetic conditions 27 days in advance, 
with high probability of successfully forecasting moder- 
ate to strong disturbances. Such forecasts on a co-oper- 
ative basis with staff members of the United States Na- 
tional Bureau of Standards and others were made by 
A. H. Shapley [75] of the Department of Terrestrial 
Magnetism during World War II, under sponsorship of 
the Wave Propagation Committee, Joint Communications 
Board, for utilization in systematic forecasts of mag- 
netic disturbance and communications conditions issued 
by the Interservice Radio Propagation Laboratory, United 
States National Bureau of Standards. The over-all accu- 
racy, as defined by the needs of this activity, was said to 
be about 65 per cent. 

Large magnetic storms and large sunspots, however, 
are successfully associated in prediction about 80 per 
cent of the time. About 80 per cent of the storms com- 
mence during the three days the spot is near the central 
meridian of the Sun. However, as in weather forecast- 
ing, information of this type is applied somewhat sub- 
jectively in present forecasts of disturbance. With ad- 
vance in our knowledge of solar phenomena and their 
effects near the Earth, there can be expected more ac- 
curate and useful forecasts in the future. 

3. Formal methods of prediction. - -Wiener [74] has 
recently made extensive analytical studies of the prob- 
lem of prediction. These provide analyses for linear 
and nonlinear prediction, in the sense of analogy with 
electrical network theory. The techniques are therefore 
most conveniently applied by special predicting machines. 

The writers have in fact made application of Wiener's 
linear prediction results to estimate future values of the 
geomagnetic variation with sunspot-cycle. These results, 
obtained on a trial basis, need not be given here, since 
our computing schemes seemed somewhat too complex 
for practical use. 

4. Measures of magnetic activity. --In prediction of 
geomagnetic changes, much use is made of the ranges in 
the most disturbed elements D, H, or Z, per three-hour 
interval. These are known as K-indices. The ranges 
are selected to correspond to a nonlinear scale of zero 
to nine. A K-index of nine indicates a strong magnetic 
storm, whereas zero denotes very quiet magnetic condi- 
tions. 

A and B of Figure 242 illustrate K-indices for a 
sunspot maximum year, 1938, and the sunspot minimum 
year, 1944. The data are arranged by solar rotations. 
It will be noted that there are at times pronounced 



375 



376 



THE GEOMAGNETIC FIELD, ITS DESCRIPTION AND ANALYSIS 



recurrence tendencies for quiet as well as disturbed 
days. 

Since the semiquantitative predictions of K -indices 
are possible from solar phenomena and also, per three- 
hour interval, from the recurrence tendency of magnetic 
bays, it is of interest to translate this information in 
terms of the three-hour range at various geographical 
points. 

Table 126 gives the K-scale at present in use at 
various magnetic observatories in different geographic 
locations. The average gamma-scale, referring to the 
most disturbed element of H, D, or Z per three-hour 
interval, depends mainly on geomagnetic latitude, except 
in auroral regions where it depends more closely upon 
the distance from the station to the average position of 
the auroral zone. 

Table 127 presents the results of Table 126 in anoth- 
er way, and indicates in percentages the frequency of 
occurrence of various three-hourly ranges having mag- 
nitudes within certain assigned limits at the several sta- 
tions for the year 1940. 

Figure 243 illustrates roughly the magnitude of the 
three -hour range in the most disturbed of the elements 
H, D, or Z which was not exceeded 80 per cent of the 
time during the year 1940. This diagram has been pre- 
pared in much the same way as those of Chapter DC re- 
lating to amplitudes of geomagnetic fluctuations and can 
be improved advantageously by use of data from addi- 
tional stations when such results become available in 
the future. 

It will be noted that Figure 243 gives results for H, 
D, or Z, but provides no information as to which of the 
three elements yields the three -hour range at any given 
interval. Actually, the element chosen to provide the 
estimates of three -hour range varies with geomagnetic 
latitude, and in auroral regions depends especially on 
the distance to the auroral zone. The choice of element 
may also be different at different times of day, since the 
three -hour range in each element will have an amplitude 
corresponding more or less closely with the amplitude 
of the disturbance daily variation. Thus the average 
amplitude of the three -hour range in each geomagnetic 
element is in fairly close proportion to that of the aver- 
age disturbance daily variation (Sd). 

Figure 244 illustrates the average magnitude of Sd 
with geomagnetic latitude, referred to an auroral zone 
adjusted to a geomagnetic latitude 69° north and south, 
for four periods of day. These curves shew that at the 
auroral zone, the largest three-hour ranges are expected 
in H, and just inside and just outside the auroral zone, 
large ranges are expected in Z during morning and even- 
ing hours. Near the center of the auroral zone, the three- 
hourly ranges are expected to be largest- in H and D, 
and small in Z. In middle latitudes, the average ranges 
in H and D are largest, and obviously those in Z, I, or 
F will be considerably smaller. Near the equator, the 
fluctuations in H and F have the largest average range, 
whereas those in Z and I are relatively small. The 
currently available K-indices thus provide a rough indi- 
cation of the probable upper limit in three -hour range in 
H, D, or Z, by use of diagrams such as Figure 243, 
which shows the amplitude of three -hour range in vari- 
ous geographical localities. Moreover, these K-indices, 
used in conjunction with the known average latitude dis- 
tribution of Sd, permits tentative conclusions respecting 
the upper limits of average disturbance in other com- 



ponents not at present recorded, such as I and F. In 
practical applications where disturbance in I and F 
might become important, the average amplitudes of Sd, 
and their latitude distributions can of course be com- 
puted from the curves of Figure 244, by resolving the 
average disturbance in horizontal and vertical intensity 
along the directions I and F. These can be further im- 
proved by reference to basic data given for Srj earlier 
in this volume (only meager data exist for south polar 
regions and these have been summarized elsewhere [76]). 

5. Relation of average auroral and geomagnetic char- 
acteristics. --It is well known that the manifestations of 
aurora and geomagnetic disturbances are more or less 
closely connected temporaly [3], near the auroral zones. 
Figures 245 and 246 give the results in percentages of a 
recent revision of data respecting the daily frequencies 
of aurora in various regions of the world [76,77]. These 
revisions were undertaken in conjunction with other studies 
of the .present volume. Figures 247 to 250 provide sim- 
ilar results newly derived for hourly frequencies of au- 
rora for the Northern Hemisphere, estimated on a like 
basis, taking into account corrections for effects of 
cloudiness, and other phenomena, on the observed fre- 
quencies of aurora. 

6. The prediction of the systematic geomagnetic var- 
iations. --It has been noted that there is in current use a 
system of K-indices descriptive of intensity of disturb- 
ance and in particular of the maximum three -hour range 
in H, D, or Z. Obviously, the three-hour range is an 
indicator only of disturbance during the three-hour inter- 
val, and it often is derived from the maximum and mini- 
mum values of a short-period fluctuation that endures 
for a shorter interval of time. In other words, the K- 
indices are in part indicators of highly transient features 
of geomagnetic field which may be regarded as super- 
posed on a number of other systematic variations. The 
variations in K-indices of course arise mainly from dis- 
turbances of type Sd or Dst. 

In estimating K-indices from magnetograms, there is 
removed almost completely the three-hour range con- 
tributed by the solar daily variation, Sq, which is present 
daily throughout low and middle latitudes and is the most 
apparent and persistent feature of the daily records. On 
the other hand, Sd, which is often very small in these 
latitudes and at times varies greatly in intensity, is re- 
flected in part in the K-indices. Thus, in practical ap- 
plications requiring precise knowledge of the geomagnetic 
field, it may be desirable to predict amplitudes of the 
solar daily variation Sq and the post-perturbation P. 

The prediction of the amplitude of S q a day or two in 
advance, with an accuracy of about 20 per cent, for the 
great majority of days, is easily achieved by a simple 
graphing procedure of daily amplitude factors of Sq such 
as those listed in Table 1-Q of the preceding volume [1]. 
In the same way, the shifts in phase of Sq from day to 
day can be successfully predicted with fair success. 

In the case of the post-perturbation P, the trend 
from day to day, as shown in Table 1-G in the earlier 
volume [1], is highly regular. Its prediction within 20 
per cent, except possibly at times of onset of marked 
disturbance, seems relatively well assured. 

It is therefore feasible in engineering applications of 
geomagnetism to take into account and reduce the limi- 
tations imposed by geomagnetic fluctuations through use 
of prediction schemes for various geomagnetic fluctua- 
tions. 



TABLES 126-129 

Table Page 

126. Contributing observatories and lower limits of ranges in D, H, or Z for three-hour 

range indices (K) 378 

127. Per cent of time that three-hour range of disturbance in D, H, or Z is less than the 

various ranges derived from three-hour range indices for 1940 from 28 observatories . 378 

128. List of abbreviations for auroral stations, Northern Hemisphere 379 

129. List of abbreviations for auroral stations, Southern Hemisphere 379 



377 



Table 126. Contributing observatories and lower limits of ranges (R) in D, H, or Z 
for three -hour -range indices (K) 



Observatory (a) 

and 
abbreviation (b) 


Geographical 
co-ordinates 


For value of K 







1 


2 


3 


4 


5 


6 


7 


8 




(a) 


(b) 


<t> 


XE 


9 



Godhavn 


Go 


69.2 


306.5 





18 


36 


72 


144 


250 


430 


720 


1200 


1800 


Sodankyla 


So 


67.4 


26.6 





10 


20 


40 


80 


140 


240 


400 


660 


1000 


College 


Co 


64.9 


212.2 





25 


50 


100 


200 


350 


600 


1000 


1650 


2500 


Dombaas 


Do 


62.1 


9.1 





8 


15 


30 


60 


105 


180 


300 


500 


750 


Lerwick 


Le 


60.1 


358.8 





10 


20 


40 


80 


140 


240 


400 


660 


1000 


Sloutzk 


SI 


59.7 


30.5 





6 


12 


24 


48 


85 


145 


240 


400 


600 


Sitka 


Si 


57.0 


224.7 





10 


20 


40 


80 


140 


240 


400 


660 


1000 


Rude Skov 


RS 


55.8 


12.5 





6 


12 


24 


48 


85 


145 


240 


400 


600 


Eskdalemuir 


Es 


55.3 


356.8 





8 


15 


30 


60 


105 


180 


300 


500 


750 


Meanook 


Me 


54.6 


246.7 





15 


30 


60 


120 


210 


360 


600 


1000 


1500 


Witteveen 


Wi 


52.8 


6.7 





5 


10 


20 


40 


70 


120 


200 


330 


500 


Niemegk 


Ni 


52.1 


12.7 





5 


10 


20 


40 


70 


120 


200 


330 


500 


Abinger 


Ab 


51.2 


359.6 





5 


10 


20 


40 


70 


120 


200 


330 


500 


Chambon-la-Foret 


CF 


48.0 


2.3 





5 


10 


.20 


40 


70 


120 


200 


330 


500 


Agincourt 


Ap 


43.8 


280.7 





6 


12 


24 


48 


85 


145 


240 


400 


600 


Cheltenham 


Ch 


38.7 


283.2 





5 


10 


20 


40 


70 


120 


200 


330 


500 


San Fernando 


SF 


36.5 


353.8 





4 


8 


16 


30 


50 


85 


140 


230 


350 


Tucson 


Tu 


32.2 


249.2 





4 


8 


16 


30 


50 


85 


140 


230 


350 


Z6-Se 


zs 


31.1 


121.2 





3 


6 


12 


24 


40 


70 


120 


200 


300 


Honolulu 


Ho 


21.3 


201.9 





3 


6 


12 


24 


40 


70 


120 


200 


300 


San Juan 


SI 


18.4 


293.9 





3 


6 


12 


24 


40 


70 


120 


200 


300 


Kuyper 


Ku 


- 6.0 


106.7 





3 


6 


12 


24 


40 


70 


120 


200 


300 


Huancayo 


Hu 


-12.0 


284.7 





6 


12 


24 


48 


85 


145 


240 


400 


600 


Apia 


Ap 


-13.8 


188.2 





3 


6 


12 


24 


40 


70 


120 


200 


300 


Watheroo 


Wa 


-30.3 


115.9 





4 


8 


16 


30 


50 


85 


140 


230 


350 


Pilar 


Pi 


-31.7 


296.1 





3 


6 


12 


24 


40 


70 


120 


200 


300 


Cape Town 


CT 


-33.9 


18.5 





3 


6 


12 


24 


40 


70 


120 


200 


300 


Amberley 


Am 


-43.2 


172.7 





5 


10 


20 


40 


70 


120 


200 


330 


500 



Table 127. Per cent of time that three-hour-range of disturbance in D, H or Z is less than 

the various ranges (R) derived from three-hour-range indices (K) for 1940 

from 28 observatories 



Observatory 


Geo- 
magnetic 
latitude 


Ranges (R) in gammas) 


5 


10 


20 


30 


50 


75 


100 


200 


500 



% 



% 



% 



% 



% 



% 



o/o 



% 



% 



Godhavn 


79.8 








1.3 


6.6 


19.0 


38.9 


55.9 


83.8 


98.3 


College 


64.5 





6.6 


19.3 


29.2 


48.8 


61.1 


69.4 


82.1 


93.6 


Sodankyla 


63.8 


3.0 


19.4 


40.8 


51.9 


63.2 


71.6 


77.6 


90.0 


97.8 


Lerwick 


62.5 





9.6 


34.6 


52.6 


71.1 


82.7 


89.3 


95.7 


98.2 


Dombaas 


62.3 


11.0 


26.1 


46.6 


61.9 


76.7 


86.8 


90.7 


96.1 


98.5 


Meanook 


61.8 





7.0 


32.7 


43.1 


57.3 


68.1 


74.9 


87.2 


96.7 


Sitka 


60.0 





16.6 


41.5 


53.6 


70.4 


80.1 


85.8 


94.1 


98.0 


Eskdalemuir 


58.5 





11.0 


40.6 


61.3 


80.4 


91.3 


94.8 


98.2 


99.5 


Sloutzk 


56.0 


2.0 


18.9 


41.1 


59.2 


79.7 


89.8 


94.6 


98.1 


99.3 


Rude Skov 


55.8 


13.8 


34.0 


55.5 


69.1 


84.5 


92.0 


95.3 


98.3 


99.5 


Agincourt 


55.0 


7.0 


28.0 


51.0 


65.9 


83.1 


90.1 


93.7 


98.1 


99.7 


Witteveen 


54.2 


12.4 


31.5 


58.2 


72.1 


87.3 


94.3 


96.7 


99.1 


99.9 


Abinger 


54.0 


1.7 


23.9 


53.3 


69.3 


87.9 


94.6 


97.1 


99.0 


99.9 


Niemegk 


52.2 


13.3 


38.0 


64.9 


76.0 


88.8 


95.0 


97.0 


99.2 


99.9 


Chambon-la-For§t 


50.4 


17.3 


43.7 


72.0 


83.3 


94.3 


97.6 


98.7 


99.8 


100.0 


Cheltenham 


50.1 


13.9 


35.0 


60.7 


73.1 


88.7 


94.8 


97.4 


99.0 


99.9 


San Fernando 


41.0 


13.8 


32.3 


60.2 


75.8 


91.1 


96.7 


98.2 


99.6 


100.0 


Tucson 


40.4 


21.1 


45.0 


70.9 


85.1 


94.6 


97.7 


98.9 


99.6 


100.0 


San Juan 


29.9 


37.5 


65.6 


86.7 


93.7 


98.0 


98.7 


99.0 


99.9 


100.0 


Honolulu 


21.1 


43.2 


66.9 


87.0 


94.6 


97.9 


99.0 


99.2 


99.9 


100.0 


ZS-Se 


19.8 


10.7 


34.3 


70.6 


86.6 


96.1 


98.3 


98.9 


99.9 


100.0 


Huancayo 


- 0.6 


9.0 


30.0 


54.6 


70.6 


86.8 


93.0 


95.5 


98.8 


99.9 


Apia 


-16.0 


25.7 


57.5 


84.7 


94.5 


97.9 


99.0 


99.2 


100.0 


100.0 


Kuyper 


-17.5 


33.0 


59.2 


82.3 


92.5 


97.0 


98.6 


99.0 


100.0 


100.0 


Pilar 


-20.2 


24.3 


48.9 


77.6 


88.9 


97.1 


98.5 


99.0 


99.9 


100.0 


Cape Town 


-32.7 


40.0 


64.3 


86.1 


94.5 


97.9 


99.0 


99.3 


99.9 


100.0 


Watheroo 


-41.8 


23.0 


48.0 


78.6 


89.8 


96.5 


98.3 


98.7 


99.6 


100.0 


Amberley 


-47.7 


9.8 


33.8 


67.2 


80.3 


92.7 


96.7 


98.1 


99.5 


99.9 



378 



Table 128. List of abbreviations for auroral stations, Northern Hemisphere 



Station 



Ab. 



Station 



Ab. 



Station 



Ab. 



Abisko 


Ab 


Gordon Castle 


GC 


New York Harbor 


Aberdeen 


Abe 


Gjoahavn 


Gj 


Oslo 


Albany 


Al 


Great Liakhovsky Is. 


GLI 


Ouellen 


Angmagsalik 


An 


Godhavn 


Go 


Point Barrow 


Blue Hill 


BH 


Godthaab 


Gt 


Pentland Skerries 


Bear Island 


BI 


Haroldswick 


Ha 


Polar Star 


Bossekop 


Bo 


Havre 


Hav 


Refuge Harbor 


Balta Sound 


BS 


Houlton 


Ho 


Russian Harbor 


Bowdoin Harbor 


BoH 


Havnefjord 


Hvn 


Rudolph Island 


Burlington 


Bu 


Ithaca 


It 


Rice Strait 


Calm Bay 


CB 


Ivigtut 


Iv 


Saskatoon 


Cape Desire 


CD 


Jacobshavn 


Ja 


Ssagastyr 


College -Fairbanks 


CF 


Jan Mayen 


JM 


Sheridan 


Chelyuskin 


Ch 


Juneau 


Ju 


Sitka 


Cape Hope's Advance 


CHA 


Kingua Fjord 


KF 


Sergei Kamenev Is 


Chesterfield Inlet 


CI 


Kirkwall 


Ki 


Sodankyla 


Cleveland 


CI 


Koutokaeino 


Ko 


Spokane 


Coppermine 


Co 


King Point 


KP 


Scoresby Sund 


Contoocooksville 


Con 


Kultala 


Ku 


Sault Ste. Marie 


Cape Otto Schmidt 


COS 


Lerwick 


Le 


Stornoway 


Cape Thordsen 


CT 


Madison 


Mad 


Sukkertoppen 


Deerness 


De 


Maud I 


Mai 


Tixi Bay 


Duntulm • 


Du 


Maud H 


Mall 


Tiree 


Edmonton 


Ed 


Maud III 


Main 


Toronto T 


Ellendale 


El 


Meanook 


Me 


Treurenberg 


Eskdalemuir 


Es 


Malya Karmakuly 


MK 


Upsala 


Floeberg Beach 


FB 


Matochkin Shar 


MS 


Vega 


Fort Conger 


FC 


Nain 


Na 


Wick 


Fort Rae 


FR 


Nennortalik 


Ne 


Wrangel Island 


Gaasef jord I 


Gal 


Northbrook Island 


NI 


Yerkes Y 


Gaasef jord II 


Gall 


Nome 


No 





NYH 
Os 
Ou 
PB 

PeS 

PS 

ReH 

RH 

RI 

RS 

Sa 

Sag 

Sh 

Si 

SKI 

So 

Sp 

SS 

SSM 

St 

Su 

TB 

Ti 

To 

Tr 

Up 

Ve 

Wi 

WI 

Ye 



Table 129. List of abbreviations for auroral stations, Southern Hemisphere 



Station 



Ab. 



Station 



Ab. 



Station 



Ab. 



Adelaide 


Ad 


Cape Schank 


CS 


Little America 


LA 


Ballarat 


Ba 


Endurance 


End 


Laurie Island 


LI 


Beechworth 


Be 


Deutschland 


Deu 


Macquarie Island 


MI 


Beleica 


Bel 


Framheim 


Fr 


New Zealand 


NZ 


Cape Adare 


CAd 


Gauss -Station 


GS 


Port Charcot 


PC 


Cape Armitage 


CAr 


Hobarton 


Ho 


Queen Mary Land 


QML 


Cape Denison 


CD 


Hut Point 


HP 


Santiago 


Sa 


Cape Evans 


CE 


He Petermann 


IP 


Scotia Bay 


SB 


Cape Royds 


CR 


Kerguelen 


Ke 


Victoria 


Vi 


Carneeie 


Car 


Kyneton 


Ky 


Wilson's Promontory 


W P 



379 



FIGURES 242-250 



Figure Page 

242(A). World-wide magnetic three-hour range indices K w , January 1 to December 30, 1938. . 382 

242(B). Weighted average of reduced indices from various observatories, December 14, 1943, 

to January 12, 1945 383 

243. Magnitude of three-hour range in the most disturbed elements D, H, Z, not exceeding 

80 per cent of the time during year 1940 384 

244. Variations with latitude of maxima and minima of geomagnetic components of disturbance 

diurnal variation for international disturbed minus quiet days (Sj)) 384 

245-246. Estimated percentage frequency of days with occurrence of aurora, clear, dark nights, 

high latitudes, Northern and Southern Hemispheres 385 

247-250. Estimated percentage frequency of hours with occurrence of aurora, clear, dark 

nights, high latitudes, Northern Hemisphere 386 



381 





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382 



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HONOLULU, HUANCAVO, AND WATHEROO, DECEMBER 14, 1943 TO JANUARY 13, 1945 



383 




FIG 243-MAGNITUDE OF THREE- HOUR RANGE IN THE MOST DISTURBED ELEMENTS D, H, Z. NOT EXCEEDING 80 PER CENT OF THE TIME DURING YEAR 1940 




384 








Si 



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FIG. 247- ESTIMATED PERCENTAGE- FREQUENCY OF HOURS WITH OCCURRENCE OF AURORA, CLEAR, 
DARK NIGHTS, HIGH LATITUDES, NORTHERN HEMISPHERE. FOR 0^ GMT 



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386 



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DARK NIGHTS, HIGH LATITUDES. NORTHERN HEMISPHERE, FOR I2h GMT 




FIG. 250- ESTIMATED PERCENTAGE- FREQUENCY OF HOURS WITH OCCURRENCE OF AURORA, CLEAR, 
DARK NIGHTS, HIGH LATITUDES, NORTHERN HEMISPHERE, FOR IB h GMT 



387 



LITERATURE CITED 



1. Vestine, E. H., L. Laporte, I. Lange, C. Cooper, and 

W. C. Hendrix. 1947. Description of the Earth s 
main magnetic field and its secular change, 1905- 

1945. Carnegie Inst. Wash. Pub. No. 578. 

2. Gauss, C. F. 1839. Allgemeine Theorie des Erdmag- 

netismus. Resultate aus den Beobachtungen des mag- 
netischen Vereins im Jahre 1838, pp. 1-57. Leipzig. 
Also, 1877, Werke, vol. 5, pp. 119-180. Gottingen. 

3. Chapman, S., and J. Bartels. 1940. Geomagnetism. 

Oxford Univ. Press. Vols. 1 and 2. 

4. Dyson, F., and H. Furner. 1923. The Earth's mag- 

netic potential. Mon. Not. R. Astr. Soc. Geophys. 
Sup., vol. 1, pp. 76-88. 

5. Schmidt, A. 1935. Tafeln der normierten Kugelfunk- 

tionen und ihrer Ableitung nebst den Logarithmen 
dieser Zahlen sowie Formeln zur Entwicklung nach 
Kugelfunktionen. Gotha, Engelhard -Rey her Verlag. 

6. Schrbdinger, E. 1943. The Earth's and Sun's perma- 

nent magnetic fields in the unitary field theory. 
Proc. R. Irish Acad., A, vol. 49, pp. 135-148. 

7. Vestine;, E. H., M. A. Tuve, and E. A. Johnson. 1940. 

Various hypotheses regarding the origin and main- 
tenance of the Earth's magnetic field. Trans. Wash- 
ington Meeting, September, 1939. Internat. Union 
Geod. Geophys., Ass. Terr. Mag. Electr., Bull. No. 
11, pp. 354-360. 

Schuster, A. 1912. A critical examination of the pos- 
sible causes of terrestrial magnetism. Proc. Phys. 
Soc, vol. 24, pp. 121-137. 

8. Vestine, E. H., L. Laporte, and C. Cooper. 1946. 

Geomagnetic secular change during past epochs. 
Trans. Amer. Geophys. Union, vol. 27, pp. 814-822. 

9. Lahiri, B. N., and A. T. Price. 1939. Electromag- 

netic induction in nonuniform conductors, and the 
determination of the conductivity of the Earth from 
terrestrial magnetic variations. Phil. Trans. R. 
Soc, A, vol. 237, pp. 509-540. 

10. Adams, L., and J. W. Green. 1931. The influence of 

hydrostatic pressure on the critical temperature of 
magnetization for iron and other materials. Phil. 
Mag., vol. 12, pp. 361-380; and Terr. Mag., vol. 36, 
pp. 161-169. 

11. Elsasser, W. M. 1939. On the origin of the Earth's 

magnetic field. Phys. Rev., vol. 55, pp. 489-498. 
1941. A statistical analysis of the Earth's internal 
magnetic field. Phys. Rev., vol. 60, pp. 876-883. 

1946. Induction effects in terrestrial magnetism. 
Part I. Theory. Part II. The secular variation. 
Phys. Rev., vol. 69, pp. 106-116; vol. 70, pp. 202-212. 

12. Balsley, Jr., J. R. 1946. The airborne magnetometer. 

U. S. Geol. Surv., Geophys. Invest., Prelim. Rept. 
No. 3, pp. 1-8. 

13. Veiling Meinesz, F. A. 1947. Shear patterns of the 

Earth's crust. Trans. Amer. Geophys. Union, vol. 
28, pp. 1-61. 

14. McNish, A. G. 1940. Physical representations of the 

geomagnetic field. Trans. Amer. Geophys. Union, 
21st Annual Meeting, II, pp. 287-291. 

15. McNish, A. G., and E. A. Johnson. 1938. Magnetiza- 

tion of unmetamorphosed varves and marine sedi- 
ments. Terr. Mag., vol. 43, pp. 401-407. 1940. De- 
termination of the secular variation in declination in 



New England from magnetic polarization of glacial 
varves. Trans. Washington Meeting, September, 1939; 
Internat. Union Geod. Geophys., Ass. Terr. Mag. 
Electr., Bull. No. 11, pp. 339-347. 

16. Moos, N. A. F. 1910. Magnetic observations made at 

the Government Observatory, Bombay (Colaba mag- 
netic data), for the period 1846 to 1905 and their dis- 
cussion. Part II. The phenomenon and its discussion. 
Bombay, Government Central Press. 

17. Schmidt, A. 1916. Ergebnisse der magnetischen Beo- 

bachtungen in Potsdam und Seddin in den Jahren 1900- 
1910. Abhandl. Kgl. Preuss. Meteorol. Inst., Band 5, 
No. 3, Berlin. 

18. McNish, A. G. 1933. The apparent effect of magnetic 

activity upon the secular variation of the Earth's 
magnetic field. Trans. Amer. Geophys. Union, 14th 
Annual Meeting, pp. 139-144. 

19. Scott, W. E. 1943. The mutual consistency of succes- 

sive monthly means of declination, Huancayo Magnet- 
ic Observatory. Terr. Mag., vol. 48, pp. 45-48. 

20. Wasserfall, K. F. 1941. Magnetic horizontal intensity 

at Oslo, 1843-1930. Terr. Mag., vol. 46, pp. 173-221. 

21. Fisk, H. W. 1931. Magnetic secular variation and so- 

lar activity. Internat. Res. Council, Third Rept. 
Comm. on Solar and Terrestrial Relationships, pp. 
52-59. 

22. Fleming, J. A., and W. E. Scott. 1943. List of geo- 

magnetic observatories and thesaurus of values. 
Terr. Mag., vol. 48, pp. 97-108; 171-182; 237-242. 
1944. List of geomagnetic observatories and the- 
saurus of values. Terr. Mag., vol. 49, pp. 47-52; 
109-118. 

23. Cynk, B. 1939. Variations in the disturbance field 

of magnetic storms. Terr. Mag., vol. 44, pp. 51-57. 

24. Schuster, A. 1889. The diurnal variation of terres- 

trial magnetism. Phil. Trans. R. Soc, A, vol. 180, 
pp. 467-512. 

25. Chapman, S. 1919. The solar and lunar diurnal var- 

iations of terrestrial magnetism. Phil. Trans. R. 
Soc, A, vol. 218, pp. 1-118. 

26. McNish, A. G. 1937. Progress of research in mag- 

netic diurnal variations at the Department of Ter- 
restrial Magnetism. Trans. Edinburgh Meeting, 
September, 1936; Internat. Union Geod. Geophys., 
Ass. Terr. Mag. Electr., Bull. No. 10, pp. 271-280. 
Terrestrial-magnetic and ionospheric effects as- 
sociated with bright chromospheric eruptions. Terr. 
Mag., vol. 42, pp. 109-122. 

27. Benkova, N. P. 1940. Spherical harmonic analysis 

of the Sq-variations, May-August, 1933. Terr. Mag., 
vol. 45, pp. 425-432. 

28. Chapman, S., and J. M. Stagg. 1929. On the variabil- 

ity of the quiet-day diurnal magnetic variation. Proc 
R. Soc, A, vol. 123, pp. 27-53; 1931, vol. 130, pp. 
668-697. 

29. Birkeland, Kr. 1908, 1913. Norwegian aurora polaris 

expedition, 1902-1903. vol. 1, part 1, pp. 39-315; 
part 2, pp. 319-551. 

30. Broun, J. A. 1861. On the horizontal force of the 

Earth's magnetism. Trans. R. Soc, vol. 22, part 3, 
pp. 511-565. 



388 



LITERATURE CITED 



389 



36 



37 



31. Bemmelen, W. van. 1895. Die erdmagnetische Nach- 

stbrung. Met. Zeit., vol. 12, pp. 321-329. 

32. Schmidt, A. 1925. Das erdmagnetische Aussenfeld. 

Zs. f. Geophysik, vol. 1, pp. 3-13. 

33. Liideling, T. F. 1899. Uber die tagliche periode des 

erdmagnetismus und der erdmagnetischen storungen 
an polarstationen. Terr. Mag., vol. 4, pp. 245-260. 

34. Stagg, J. M. 1935. Aspects of the current system 

producing magnetic disturbance. Proc. R. Soc, A, 
vol. 152, pp. 277-298. 

35. Slaucitajs, L., and A. G. McNish. 1937. The field of 

magnetic storms as deduced from the mean differ- 
ence of magnetic intensity on quiet and disturbed 
days. Trans. Edinburgh Meeting 1936, Internat. 
Union Geod. Geophys., Ass. Terr. Mag. Electr., 
Bull. No. 10, pp. 289-301. 

Forbush, S. E. 1938. On cosmic-ray effects associ- 
ated with magnetic storms. Terr. Mag., vol. 43, 
pp. 203-218. 

Vestine, E. H., and S. Chapman. 1938. The electric 
current system of geomagnetic disturbance. Terr. 
Mag., vol. 43, pp. 351-382. 1940. The disturbance 
field of magnetic storms. Trans. Washington Meet- 
ing, 1939, Internat. Union Geod. Geophys., Ass. 
Terr. Mag. Electr., Bull. No. 11, pp. 360-381. 

38. Vestine, E. H. 1938. Asymmetrical characteristics 

of the Earth's magnetic disturbance field. Terr. 
Mag., vol. 43, pp. 261-282. 

39. Silsbee, H. B., and E. H. Vestine. 1942. Geomagnet- 

ic bays, their frequency and current systems. Terr. 
Mag., vol. 47, pp. 195-208. 

40. Hartnell, G. 1922. Horizontal-intensity variometers. 

Dept. of Commerce, U. S. Coast and Geod. Surv., 
Spec. Pub. No. 89, Serial No. 212. 

41. Bateman, H. 1932. Partial differential equations of 

mathematical physics. Cambridge Univ. Press, p. 49, 

42. La Cour, D., and V. Laursen. 1930. Le variometre 

de Copenhague. Copenhagen, Met. Inst., Comm. 
Mag. No. 11, pp. 1-11. La balance de Godhavn. Bal- 
ance magne'tique a l'aimant monade dans d l'air 
rarefie. Comm. Mag. No. 8, pp. 1-27. 

43. Standard handbook for electrical engineers. 1941. 

A. E. Knowlton, editor-in-chief. McGraw Hill Book 
Co., New York. Seventh edition, p. 235. 

44. Stewart, B. 1861. On the great magnetic disturbance 

which extended from August 28 to September 7, 1859, 
as recorded by photography at the Kew Observatory. 
Phil. Trans. R. Soc, A vol. 151, pp. 423-430. 

45. Kohlrausch, F. 1896. Uber sehr rasche Schwankung- 

en des Erdmagnetismus. Wied. Ann., vol. 60, pp. 
336-339. 

46. Arendt, T. 1896. Des Wetter, vol. 13, pp. 241-253, 

265-280. 

47. Eschenhagen, M. 1897. On minute, rapid, periodic 

changes of the Earth's magnetism. Terr. Mag., 
vol. 2, pp. 105-114. 

48. Birkeland, Kr. 1901. Re"sultats des recherches mag- 

n^tiques faites par l'exp&lition Norwegienne de 1889- 
1900 pour r-dtude des Aurores Bore"ales, Arch. Sci. 
Phys., Geneve, vol. 12, pp. 565-586. 

49. Bemmelen, W. van. 1899. Spasms in the terrestrial 

magnetic force at Batavia. Proc. K. Akad. Wet., 
pp. 202-211. 

50. Terada, T. 1917. On rapid periodic variations of 

terrestrial magnetism. J. Coll. Sci. Imp. Univ., 
Tokyo, vol. 37, pp. 1-85. 



51. Aschenbrenner, H., and G. Goubau. 1936. Eine 

Anordnung zur Registrierung rascher magnetischer 
Storungen. Hochfrequenztech, Leipzig, vol. 47, pp. 
177-181. 

52. Schindelhauer, F. 1928, 1929. Uber elektromagne- 

tische Storungen. Elektr. Nachr.-Technik. vol. 5, 
pp. 442-449; vol. 6, pp. 231-236. 

53. Sucksdorff, E. 1936. Occurrences of rapid micro- 

pulsations at Sodankyla during 1932 to 1935. Terr. 
Mag., vol. 41, pp. 337-344. 

54. Rolf, B. 1931. Giant micropulsations at Abisko. 

Terr. Mag., vol. 36, pp. 9-14. 

55. Harang, L. 1939. Pulsations in an ionized region at 

height of 650-800 km during the appearance of giant 
pulsations in the geomagnetic records. Terr. Mag., 
vol. 44, pp. 17-19. 

56. Fleming, J. A. 1939. Physics of the Earth, vol. 8, 

Terrestrial magnetism and electricity, pp. 370-376. 

57. Wells, H. W., J. M. Watts, and D. E. George. 1946. 

Detection of rapidly moving ionosphere clouds. 
Phys. Rev., vol. 69, pp. 540-541. 

58. General Electric Instructions 14903. 1941. Photo- 

electric recording fluxmeter. General Electric Co., 
Schenectady, N. Y. 

59. Marburger, W. G. 1942. The design of a magnetic 

storm recorder. Navy Ord. Lab. Memo. No. 1430. 
Navy Yard, Washington, D. C. 

60. Marburger, W. G. 1942. The adjustment and calibra- 

tion of a magnetic storm recorder. Navy Ord. Lab. 
Memo. No. 1777. Navy Yard, Washington, D. C. 

61. Campbell, E. A. 1942. Frequency response of mag- 

netic storm recorder. Navy Ord. Lab. Memo. No. 
2104. Navy Yard, Washington, D. C. 

62. Chapman, S. 1918. An outline of a theory of mag- 

netic storms. Proc. R. Soc, A, vol. 95, pp. 61-83. 

63. Chapman, S. 1927. On certain average character- 

istics of world-wide magnetic disturbance. Proc. 
R. Soc, A, vol. 115, pp. 242-267. 

64. Chapman, S. 1935. The electric current systems of 

magnetic storms. Terr. Mag., vol. 40, pp. 349-370. 

65. McNish, A. G. 1938. Heights of electric currents 

near the auroral zone. Terr. Mag., vol. 43, pp. 67-75. 

66. Hess, V. F., and A. Demmelmair. 1937. World-wide 

effect in cosmic-ray intensity, as observed during a 
recent magnetic storm. Nature, vol. 140, pp. 316-317. 

Stormer, C. 1911. Sur les trajectoires des corpus- 
cules e'lectrise's dans l'espace sous l'action du mag- 
ne"tisme terrestre avec application aux aurores 
boreales. Arch. Sci. Phys., vol. 32, pp. 415-436. 

Chapman, S. 1937. Cosmic rays and magnetic 
storms. Nature, vol. 140, pp. 423-324. 

Angenheister, G. 1924. Die erdmagnetischen Stor- 
ungen nach den Beobachtungen des Samoa-Observa- 
toriums. Gottingen, Nachr. Ges.Wiss., pp. 1-42. 

Birkeland [29]; Brown [30]; van Bemmelen [31]; 
Schmidt{32]; Forbush [36]; Vestine and Chapman 
[37]; Chapman [62], 

67. Wells, H. W. 1942. Polar radio disturbances during 

magnetic bays. Unpublished report. 

68. Appleton, E. V. 1933. Radio observations during the 

International Polar Year, 1932-33. Proc R. Inst., 
vol. 28, pp. 1-17. 

69. Berkner, L. V., and S. L. Seaton. 1940. Ionospheric 

changes associated with the magnetic storm of 
March 24, 1940. Terr. Mag., vol. 45, pp. 393-418. 



390 



LITERATURE CITED 



70. Berkner, L. V., and H. W. Wells. 1938. Nonseasonal 

change of F2-region ion-density. Terr. Mag., vol. 
43, pp. 15-36. 

Harang, L. 1938. Annual variation of the critical 
frequencies of the ionized layer at Tromso during 
1937. Terr. Mag., vol. 43, pp. 41-43. 1939. Annual 
variation of the critical frequencies of the ionized 
layers at Tromso during 1938. Terr. Mag., vol. 44, 
pp. 15-16. 

71. Forbush, S. E. 1938. On world-wide changes in cos- 

mic ray intensity. Phys. Rev., vol. 54, pp. 975-988. 

72. Forbush, S. E. 1946. Three unusual cosmic ray in- 

creases possibly due to charged particles from the 
Sun. Phys. Rev., vol. 70, pp. 771-772. 

73. Gartlein, C. W. 1945. Progress report on the Na- 

tional Geographic Society-Cornell University study 



of aurora. Trans. Amer. Geophys. Union, vol. 26, 
pp. 119-122. 

74. Wiener, N. 1942. The extrapolation, interpolation, 

and smoothing of stationary time series with engi- 
neering applications. Mass. Inst. Tech., Cambridge, 
Mass., pp. 1-173. 

75. Shapley, A. H. 1944. An estimate of the trend of 

solar activity, 1944-1950. Terr. Mag., vol. 49, 
pp. 43-45. 

76. Vestine, E. H., and E. J. Snyder. 1945. The geo- 

graphic incidence of aurora and magnetic disturb- 
ance, Southern Hemisphere. Terr. Mag., vol. 50, 
pp. 105-124. 

77. Vestine, E. H. 1944. The geographic incidence of 

aurora and magnetic disturbance, Northern Hemis- 
phere. Terr. Mag., vol. 49, pp. 77-102.