. e

LJ. of Iowa 66-12

*

The Temporal Variations of Electron I n t e n s i t i e s a t Low Alti tudes i n the

Outer Radiation Zone as Observed with S a t e l l i t e Injun 3

Department o f FhysIcs and Astronomy university o f Iowa Iowa City, Iowa

--

April 1966

Researc.. supported i n p a r t by the 0 ?e o Nava A,2search under cont rac ts Nonr-1509(06) and Ngonr 93803.

Graduate Research Fellow o f the National Aeronautics and Space Administration.

**

Distr ibut ion of t h i s document i s u n l i m i t e d .

https://ntrs.nasa.gov/search.jsp?R=19660021301 2020-08-05T23:06:03+00:00Z

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ABSTRACT

1 Temporal var ia t ions of the i n t e n s i t i e s of electrons

(E > 40 keV, > 230 keV, > 1.6 MeV) trapped i n the outer r ad ia t ion

zone i n the region 3.0 - - < L < 6.0 and mirroring a t a l t i t u d e s of

- 1500 ?an have been studied during a seven-month period from

January 1 t o July 31, 1963, by means of th ree Geiger-Mueller

tubes on-board the U . of Iowa/Office of Naval Research research

s a t e l l i t e Injun 3. From observations during some twenty geomag-

n e t i c a l l y disturbed periods, it i s shown t h a t the l a r g e s t i n t e n s i t y

var ia t ions C'CCUI" a t the onset o f such disturbances and t h a t sub-

sequent behavior is dependent on the magnitudes of t he disturbances

as measured by the maximum d a i l y sums o f t h e planetary magnetic

disturbance parameter, K . The time h i s t o r i e s of these i n t e n s i t y

va r i a t ions rre compard with those of 3-hour averages o f t he P

horizontal component of t he geomagnetic f i e l d a t College, Alaska

(L = 5 .5 ) , f o r severa l disturbed periods.

Nearly simultaneous measurements of the d i r ec t iona l

i n t e n s i t i e s of e lec t rons (E > 40 keV), which mirror a t low

a l t i t u d e s , with Injun 3, and omnidirectional i n t e n s i t i e s of these

e l ec t rons near the geomagnetic equator ia l plane, with Explorer 14,

. e

3

ind ica te s imi la r temporal behavior a t L - 4 .

observed i n t e n s i t i e s of trapped electrons (E > 40 keV) i n the

outer zone a t low a l t i t u d e s appear t o occur under a condition

of approximate isotropy and equal omnidirectional i n t e n s i t i e s

< 10 (em -see)

above severa l hundreds of kilometers.

The highest

8 2 -1 along a magnetic f i e l d l i n e a t a l l alt,:tudes N

During four periods of post-disturbance geomagnetic calm,

the i n t e n s i t i e s of electrons ( E > 40 keV) were observed by

Injun 3 t o decrease exponentially i n t i m e with decay constants

T = 12 - + 3 days a t L = 3.0, and 7 = 4 - + 2 days i n the region

3.5 5 L - < 6 . C .

constants f o r these electron i n t e n s i t i e s near t h e geomagnetic

equa to r i a l plane a t L - 4 agree, within gbservational e r r o r .

Long-term exponential ciecays in the i n t e n s i t i e s of a r t i f i c i a l l y

in j ec t ed electrons (E > 1.6 MeV) were observed by Injun 3 t o be

characterized by 7 = 40 - + 5 and 45 - + 5 days a t L = 3.0 and 3.5,

respec t ive ly .

Simultaneously measured values of the decay

Further evidence f o r the diffusion of e lec t rons

( E > 1.6 MeV) i s presented.

4

I. Introduction

The observations of a quasi-thermalized plasma with

omnidirectional i n t e n s i t i e s of electrons (E > 100 eV) of the

order of 2 x 10 (em -see) [Serbu, 19651 , some tens of e rgs

(em -see) of e lec t rons (E - 1 keV) [Freeman, Van Allen, and

Cahi l l , 19631 and frequent i so la ted "spikes1' o f e lec t rons

0 2 -1

2 -1

5 2 -1 (40 < E < 200 keV) with i n t e n s i t i e s below - 10 (em -see)

[Frank and Van Allen, 15641 a t t h e sunward boundary of the

magnetosphere within t h e magnetosheath, or trans: t i o n region,

and the Observations of an abrupt decrease i n the i n t e n s i t i e s

of e lec t rons (E > 100 eV) a t the shock boundary [Serbu, 19651

and the infrequent so l a r emission o f observable i n t e n s i t i e s of

e lec t rons (E > 40 keV) [Van Allen and Krimigis, 19651 demonstrate

the heating and p a r t i a l confinement of the low energy e l ec t ron

component of the s o l a r plasma. The observations of high

i n t e n s i t i e s of e l ec t r zns (E > 40 keV) throughout the magnetosphere

(Jo (E > 40 keV) - 105-8 (cm2-sec) and i n t e n s i t i e s of e lec t rons

(E > 230 keV, > 1.6 MeV) which i n t he hea r t of t he outer r ad ia t ion

zone reach l e v e l s of J o ( E > 230 keV) - 5 x 10

J (E > 1.6 MeV) - 10 and Craven, 19631 demonstrate t ha t mechanisms of p a r t i c l e accelera

t i o n and propagation must e x i s t within t h e magnetosphere, which

-1

6 2 -1 (cm -see) and

( e m -see)-' [Frank, Van Allen, Whelpley, 6 2 0

5

energize and d i s t r i b u t e the lower energy p a r t i c l e s found within

the t r ans i t i on and magnetospheric t a i l regions, t o produce the

observed d i s t r ibu t ions of p a r t i c l e i n t e n s i t i e s . The i n i t i a l

observations of l a rge sca l e temporal v a r i a t i o n s i n the i n t e n s i t i e s

of e lec t rons (E > 1.2 MeV) i n the o u t e r r ad ia t ion zone with the

low a l t i t u d e s a t e l l i t e Explorer 7 [Forbush, Venkatesan, and

McIlwain, 1961; Forbush, P izze l la , and Venkatesan, 19621 as well

as small sca le va r i a t ions i n the inner r ad ia t ion zone p a r t i c l e

i n t e n s i t i e s [P izze l la , McIlwain, and Van Allen, 19621, and sub-

sequent observations of these temporal va r i a t ions i n the

i n t e n s i t i e s of e lec t rons (E > 40 keV, > 230 keV, > 1.6 MeV) i n

the outer zone near t he geomagnetic equa to r i a l plane [Frank,

Van Allen, and H i l l s , 19641, trapped e lec t rons (E > 280 keV,

> 1.2 ?.lev) z i r r n r i n g a t low a l t i t udes i n the outer z m e

[Williams and Smith, 19651 and p rec ip i t a t ing e lec t rons ( E > 40 keV)

from t h e outer zone [O'Brien, 19641 fu r the r require t h a t such

accelerat ion mechanisms operate over a l a rge dynamic range and

be capable of operating e f f ec t ive ly within times of the order

of minutes t o hours.

Current candidate s f o r such " l o c all' a c c e l e r a t i on mechanisms

are magnetospheric e l e c t r i c f i e l d s [e .g. , Axford, 1962; Speiser,

1965; Taylor and Hones, 19651 and ad iaba t i c trans-L diffusion

6

[Kellogg, 1959; Parker, 1960; Herlofson, 1960; Davis and Chang,

1962; Nakada, Dungey, and H ~ s s , 19641.

t ions ind ica te t h a t e l e c t r i c f i e l d s may e x i s t with s u f f i c i e n t

The t h e o r e t i c a l computa-

s t rength t o acce lera te e lec t rons t o energies of several tens of

ki loelectron v o l t s . The observations of the apparent r a d i a l

d i f fus ion of e lec t rons (E > 1 . 6 MeV) a t L .-- 3-5 by Frank 11965bl

and of protons (40 > E > 110 MeV) a t L .-- 2.2 by McIlwain [19651

a re suggestive of such processes.

The present paper presents the r e s u l t s of an invest igat ion

cf t h e temporal var ia t ions of t he i n t e n s i t i e s of e lec t rons

(E > 40 keV, > 230 keV, > 1.6 MeV) trapped i n the outer r ad ia t ion

zone and mirroring a t l o w a l t i t udes as observed by the U. of Iowa/ONR

research s a t e l l i t e Injun 3 during the period January 1 t o J u l y 31, 1963

7

11. Description of the Experiment

The University of Iowa research s a t e l l i t e Injun 3 (1962

beta-tau) was launched on December 13, 1962, i n t o an o r b i t whose

i n i t i a l parameters were an apogee a l t i t u d e of 2785 km, a perigee

a l t i t u d e of 237 km, an o r b i t a l inc l ina t ion of 70.4" and a period

o f 116 minutes.

l o c a l geomagnetic f i e l d vector, B, by an on-board permanent magnet.

Throughout i t s useful l i f e t ime o f some nine months, data per ta ining

t o the or ien ta t ion [ F r i t z , 19651 and the operating voltages and

temperatures were rout inely monitored. A system of on-board so la r

aspect sensors indicated those times when data from d i r ec t iona l

de tec tors s ens i t i ve t o l i g h t and/or s o l a r x-rays were being con-

taminated. A descr ipt ion o f the complete Injun 3 s a t e l l i t e i s

given by O'Brien, Laughlin, and Gwnett [1$41.

The s a t e l l i t e was oriented with respec t t o the +

This paper i s csncerned with da ta obtained from three

Geiger-Mueller tubes which were par t o f t he Injun 3 rad ia t ion

experiment. They are: 213A, a thin-windowed (- 1 . 2 mg cm mica)

Anton 213 G.M. tube, whose 13' half anglr conical f i e l d of view

i s centered on a l i n e normal t o g, when the s a t e l l i t e i s properly

or ien ted ; 213B, a G.M. tube which i s i d e n t i c a l t o 213A with the

-2

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r

exception of an addi t ional 48 mg cm9 of aluminum over the

viewing window; 302, an Anton 302 G.M. tube surrounded by

265 mg c m of magnesium. The physical parameters associated

with these instruments are tabulated i n Table I .

-2

The t r u e versus apparent ( R vs r ) counting r a t e ca l ibra-

t i ons of these instruments were performed by doing a s e r i e s of

overlapping inverse-square ca l ibra t ions , u t i l i z i n g a Westinghouse

Quadrocondex x-ray machine. The dynamic ranges of t he G.M. tube

b cour,ting ra tes were grea te r than 3 x 10 . Allowing f o r the

temperature and voltage coef f ic ien ts of the instruments, the

R vs r curves are considered accurate t o within 20% f o r 302

when r < 10

3 r < 5 x 10

l e a s t accurate. T%e accuracjes of the curves decrease a t higher

counting r a t e s , being - 50% fo r 302 when r - 2 x 10

for 2 1 3 A when r - 1.3 x 10

4 counts (see)-’ and for 213A and 213B when

counts (sec)-’, the higher counting r a t e s being the

4 -1 counts ( sec) , 4 counts (see)-’ and f o r 213B when

r - 8 x 10 3 counts (see)-’.

The e f f i c i enc ie s of G.M. tubes f o r t he detect ion of non-

penetrat ing electrons have been studied i n d e t a i l by t h i s laboratory

[e .g . , Frank, 19621, and a summary of such work, f o r s eve ra l of the

G.M. tubes of t h e type used on Injun 3, i s presented i n Figure 1.

. 9

From t h i s data, nominal threshold energies and geometric

f a c t o r s have been obtained by numerically evaluating an i n t e g r a l

of t he form

where E (E) i s the exrpirically determined efficiency, i n counts

(e lectron)

t r a t i n g e lec t rons and dj/dE i s the d i r ec t iona l d i f f e r e n t i a l

i n t e n s i t y spectrum assumed. For the 3G2, corresponding omni-

-1 , g i s the d i r ec t iona l geometric f ac to r f o r pene-

d i r ec t iona l quan t i t i e s a re used. The quant i ty

which i s the r e l a t i v e contribution t o the t o t a l counting of t he

G.M. tube, due t o e lec t rons of energy g rea t e r than E when the

d i f f e r e n t i a l i n t e n s i t y spectrum i s of t he form AE-', has beer,

computed fo r a s e l ec t ion of spectra .

are summarized i n Table 11, and the forms of t he observed energy

From these r e s u l t s , which

spec t ra , the following conclusions have been made f o r a l l events

)bserved during t h i s study: (1) 213A i s responding pr imari ly

10

t o e lec t rons with E > 40 keV and has an e f f e c t i v e cg of 4 x lo-’

count-cm2-sr (e lec t ron) , and (2) 302 i s responding pr imari ly

t o e lec t rons with E > 1.6 MeV and has an e f f e c t i v e €GO of

0.1 count-cm2 (e lec t ron) .

-1

-1

A revaluation o f t he e f f i c i enc ie s of 213B-type Geiger

tubes is i n progress, but the r e s u l t s are not expected t o d i f f e r

i n any important way from those previously known, t h a t i n the

outer zone the 213B responds P r h a r i l Y t o e lec t rons with

E > 230 keV with an e f f e c t i v e E g of 4 x c o u n t - c m 2 - s r & ~ ~ ~ !

Iden t i f i ca t ion of t h e charged p a r t i c l e s observed by t h e

three G . M . tubes was made by comparing t h e i r i n t e n s i t i e s with

those measured with complementary experiments on-board Injun 3.

The p-n junction experiments, which measured the e n e r a sp2ctrum

and d i r ec t iona l h t e n s l t i e s zf protons (700 keV < E < 100 MeV)

(da ta the courtesy of C . Bostrom and G . Pieper, The Applied

Physics Laboratory, Johns Hopkins University) ind ica te t h a t f o r

any reasonable proton spectra there a r e no important contributions

t o t h e responses of 213A and 213B due t o protons (E > 500 keV) and

( E > 4 MeV), respectively, i n the region L > - 3 fo r the da ta used

i n t h e present inves t iga t ion . These r e s u l t s , plus the data

obtained from the near ly omnidirectional pulse s c i n t i l l a t o r

experiment which rSsponded to prntons ( E > 40 MeV) (data t h e

courtesy of C . McIlwain, Department of physics, University of

California a t San Diego, La Jo l l a , California) have shown t h a t

the 302 was responding primarily t o e lectrons ( E > 1.6 MeV).

111. Data Analysis

Data telemetered by the Injun 3 s a t e l l i t e were received

by a large network of ground s ta t ions and recorded on magnetic

tape along with o r a l time ver i f ica t ions and, when possible, WWV.

These data tapes were then sent t o the University of Iowa for

decoding and merging with ephemerides computed by the Goddard

Space F l ight Center of NASA. A master data tape was then

compiled which, with each eight second average of the experimental

data, contained the following information: universal time,

s a t e l l i t e clock time, geographic l o c a l time, geographic l a t i t u d e ,

longitude and a l t i t u d e , B and L, B/Bo, s o l a r aspect and magnetic

or ien ta t ion data, revolution number, receiving s t a t i o n i d e n t i f i c a -

t i o n code and various housekeeping da ta . With t h i s master data

tape it was possible t o s o r t and s e l e c t the data i n any desired

manner.

For t h i s study, the data were orgacized i n several manners.

F i r s t , i n order t o study the temporal var ia t ions o f the e lec t ron

i n t e n s i t i e s a t f ixed points i n B-L space [McIlwain, 19611 (which

i s assumed t o be an equally va l id coordinate system during geomag-

n e t i c a l l y calm and disturbed times i n the region L < 7 ) for the

seven-month period under investigation, the data were sor ted on

-

13

L and divided i n t o non-overlapping blocks whose dimensions were

0.5 L and which were centered on integer and half- integer values

of L. Each block of data was then sor ted on B, wi th dimensions

of 0.02 gauss, forming a data matrix i n B and L,each element of

which was then ordered i n t i m e . To s tudy the var ia t ions f o r

seven consecutive months, one datum per twelve hours a t a se lec ted

value of L - + 0.1 and a t t he lowest value of B which was ava i lab le

was se lec ted from t h e data matrix f o r each G.M. tube and p lo t t ed

aga ins t time. During several periods of increased geomagnetic

a c t i v i t y , observations of t he temporal behavior of the e lec t ron

i n t e n s i t i e s were made with a time resolut ion of severa l hours

by se l ec t ing a l l avai lable data a t a f ixed L 2 0.1 and p l o t t i n g

it aga ins t time.

c a r e f u l l y s tudied . I n these cases the dependence on B must be

The L dependence of the temporal va r i a t ions of the outer

zone e lec t ron i n t e n s i t i e s was fu r the r s tudied by choosing s e t s of

nea r ly iden t i ca l passes through the outer zone and comparing the

day t o day changes in those i n t e n s i t i e s . Any s e t of passes, which,

f o r any given value of L i n the ou te r zone, has t h e same value of

B, t o within - 0.01 gauss, a re termed near ly iden t i ca l . These

passes occurred once every - 24. hours, and s e t s of 8-12 passes

were typ ica l .

14

Data were accepted only when the s a t e l l i t e was within 10'

of alignment with the l o c a l geomagnetic f i e l d vector and data

contaminated by so la r x-rays were eliminated. Corrections due t o

changes i n operating voltages and temperatures were not necessary.

A summary of t he ground s t a t ions which were ac t ive i n

receiving telemetry from In jun 3 , and a breakdown by month of

the number of passes through the outer zone for which da ta e x i s t

has been published [Frank, Van Allen, and Craven, 19641. summary, it shows t h a t - 9% of the da ta ava i lab le for study were

obtained when Injun 3 was over o r near the North American

Continent.

I n

.

IV. Presentat ion of Data

1. The Temporal Variations of the I n t e n s i t i e s of Electrons (E 7 40 keV)

The temporal var ia t ions of the i n t e n s i t i e s of e lec t rons

(E > 40 keV) trapped i n t h e outer rad ia t ion zone have been s tudied

a t low a l t i t u d e s with the 213A G.M. tube on Injun 3 f o r t he seven-

month per iod from January 1 t o Ju ly 31, 1963. The responses of

213A t o these e lec t rons a r e presented i n Figure 2. The d i f f e r e n t

ranges of B a r e indicated by appropriate symbols, which a r e defined

there in .

3.5, 4.0, 4.5, 5.0, and 6.0.

sums of the p lane tary disturbance parameter, K

hereaf te r denoted by CK

cor re la ted wi th the i n t e n s i t i e s of e lec t rons (E > 4.0 keV) near

t h e geomagnetic equator ia l plane [Frank, Van Allen, and H i l l s ,

19641 and with the solar wind ve loc i ty [Snyder, Neugebauer, and

Rae, 19631.

The values of L f o r which da ta were assembled were 3.0,

Included are the corresponding d a i l y

[Lincoln, 19631,

which has been shown t o be pos i t i ve ly P

P’

The s t r i k i n g p a r a l l e l between periods of enhanced e lec t ron

i n t e n s i t i e s and increased geomagnetic a c t i v i t y , as measured by

CK i s self-evident: with each new geomagnetic disturbance, P’

16

there occurs an abrupt increase i n the i n t e n s i t i e s of e lectrons

(E > 40 keV) trapped i n the outer zone, followed by a monotonic

decrease i n the i n t e n s i t i e s as the disturbance subsides. The

increases i n i n t e n s i t i e s i n the heart of the outer zone,

i . e . , L - 4.5, a re typ ica l ly - 10 - 10-15 greater than the typ ica l pre-disturbance i n t e n s i t i e s of

- 7-10 x 10

of the i n t e n s i t i e s of trapped electrons (E > 40 keV) a re found

t o be s m a l l i n magnitude, with changes of a fac tor of - 2 being

typ ica l , and, unlike those occurring a t higher L, a r e general ly

of a gradual nature, occurring over many days. Increases i n

i n t e n s i t i e s a t L = 3.0 a r e observed only in associat ion with the

more intense geomagnetic disturbances (c f . March 7-14, l S 3 ) .

During smsller disturbances the in t ens i t i e s appear t o be gradually

decreasing.

a t L = 6.0 display a temporal behavior which is s i m i l a r t o t ha t

observed i n the hea r t of the outer zone a t L - 4.5, although the

i n t e n s i t i e s appear t o be s l i g h t l y more sens i t ive t o var ia t ions i n

6 2 -1 (cm -sec-sr) , or a fac tor of

4 2 (cm -sec-sr)-'. A t L = 3.0 the temporal var ia t ions

"he i n t e n s i t i e s of trapped electrons (E > 40 keV)

. The several "short-lived" decreases i n the i n t e n s i t i e s of CKP these electrons a t L = 6.0 near the beginning of two geomagnetic

disturbances i n July, where the data a r e p l e n t i f u l , a r e most

curious. These observations are discussed i n a l a t e r por t ion

of t h i s repor t .

A close study of Figure 2 reveals an in t e re s t ing r e l a t i o n

between the observed enhancements of t h e i n t e n s i t i e s of e lec t rons

(E > 40 keV) trapped i n the outer zone andCK as i s demonstrated

by the data a t L = 4 .O fo r April, 1963. That i s , t he more intense

a geomagnetic disturbance, a s measured by the maximum CK observed

during each such disturbance, and hereaf te r denoted by MAXXK

the grea te r the increase i n the in t ens i t i e s of e lectrons (E > 40 keV)

trapped i n t h e outer zone a t t he onset of the disturbance. A study

of t h i s cor re la t ion a t a spec i f i c L, say L = 4.5 t 0.1, ind ica tes

presence of the pos i t ive correlat ion, but a more c l e a r l y defined

cor re la t ion , w i t h a minimum of data s c a t t e r , is possible by taking,

f o r each enhancement, t he average increase i n i n t e n s i t i e s i n the

region 3.5 < - - L < 5.0, as measured by taking the average of the

increases a t L = 3.5, 4.0, 4.5, and 5.0, and associat ing t h i s

average with the corresponding W K f o r t he disturbance.

P’

P

P’

P

These r e s u l t s a r e presented i n Figure 3, where it can be

seen t h a t t he temporal var ia t ions of t he i n t e n s i t i e s of e lectrons

. 18

(E > 40 keV) a r e only marginally observable i n the outer zone

f o r geomagnetic disturbances characterized by MAXCK <, 15,

while fo r very intense events, MAXCK > 35, the increases i n

i n t e n s i t i e s become only weakly dependent on W K , possibly

ind ica t ing approach t o some l imi t ing value.

P

P "

P

Although some 22 geomagnetic disturbances and the corre-

sponding temporal behavior of t h e i n t e n s i t i e s of e lectrons

(E > 40 keV) trapped i n the outer zone were observed during the

seven months under study, it was not always possible t o determine

the t i m e r a t e of decay of these electron i n t e n s i t i e s a t Injun 3

a l t i t u d e s during periods of what might be termed "the quie t

geomagnetic f i e l d " , s ince new disturbances would introduce a

supply of "fresh" e lec t rons ( E > 4.0 keV) and thus mask the decay

which followed the previous enhancement. There were, however,

severa l geomagnetic disturbances which were followed by extended

periods of low K f o r which the time r a t e of decay of the in te -

s i t ies of e lec t rons (E > 4.0 keV) have been measured a t low P

a l t i t u d e s i n t h e outer zone. For these events, the i n t e n s i t i e s

have been represented by

jL (E > 4.0 keV, t ) = jl ( E > 40 keV, 0) e(-t /T),

and the decay constant, T , obtained f o r various values of

L. The r e s u l t s a r e t o be found in Figure 4, where it can be

seen t h a t t h e values of T l i e between 2 and 6.5 days for

3.5 < - - L < 6.0, but increase rap id ly a t l e s s e r L .

l a rge r values of T obtained a t L = 4.0 and 4 .5 i n March, and a t

5.0 and 6.0 i n February may be due t o small in jec t ions of "fresh"

electrons .

The s l i g h t l y

As Injun 3 only sampled t h e i n t e n s i t i e s of trapped outer

zone e lec t rons (E > 40 keV) which mirrored a t low a l t i t u d e s and

whose equator ia l p i t c h angles were < 5 O , it was desirable t o

attempt t o expand these r e s u l t s t o include a l l equa tor ia l p i t c h

angles, by comparing point by point the Injun 3 data with s i m u l -

taneous measurements by s i m i l a r experiments i n the outer zone and

near the geomagnetic equator ia l plane. The published Explorer 14

data of Frank [1$5a], which gives t h e spin-averaged omnidirectional

i n t e n s i t i e s o f e lec t rons (E > 40 keV) near the geomagnetic equator ia l

plane a t L = 4.2 have been compared with t h e near ly simultaneous

In jun 3 data a t L = 4..0. The results a re displayed i n Figure 5.

A s t h i s i s considered only a preliminary study of t he simultaneous

measurement of t he i n t e n s i t i e s of these electrons, t he small

difference i n L is neglected, t he measurements are simultaneous

only t o within - 24 hours and any l o c a l time dependence which

might be present, due t o t h e s a t e l l i t e s being a t d i f f e ren t l o c a l

hr

20

times a t the time o f individual measurements, i s neglected. It

can be seen t h a t while temporal var ia t ions corresponding t o

increases i n i n t e n s i t i e s by fac tors o f 15 have been observed, the

s c a t t e r of the data is, with few exceptions, always l e s s than a

f ac to r of 2 f r o m t h e median. The medians of the r a t i o s of t he

equator ia l omnidirectional i n t ens i t i e s t o the low a l t i t u d e uni-

d i r ec t iona l i n t e n s i t i e s were 32 and 14. f o r j (E > 4.0 keV) = A

7.4 2 2.5 x 10 4 and 12 + 4 x 10 5 2 (cm -sec-sr)-’, respect ively. - From t h e same s e t of Explorer data, T has been measured

and i s compared with the corresponding values measured a t low

a l t i t u d e s i n Table 111. The agreement appears t o s t rongly

support the arguments f o r a c lose associat ion between equator ia l

i n t e n s i t i e s of e lec t rons (E > 40 keV) i n the outer zone and t h e

corresponding i n t e n s i t i e s a t l o w a l t i t udes .

2 . The Temporal Variations of t he I n t e n s i t i e s of Electrons (E > 230 keV)

The responses o f the 213B G.M. tube due t o the i n t e n s i t i e s

of e lec t rons (E > 230 keV) trapped i n the outer zone during the

same period, and subject t o t h e same method of ana lys i s as f o r t he

213A G.M. tube, a re presented i n Figure 6. As i n the case of t he

21

i n t e n s i t i e s of e lectrons (E > 4.0 keV), the i n t e n s i t i e s of

e l ec t rons (E > 230 keV) demonstrate cha rac t e r i s t i c temporal

va r i a t ions which can be cor re la ted with the temporal behavior

of CK . However, as these var ia t ions a re not always c l e a r l y

defined i n Figure 6, as t h e t i m e resolut ion of the data i s , a t

times, comparable t o t h e time scale of the var ia t ions being

observed, and the allowed spread i n L (2 0.1) i s too la rge f o r

L < - 4..0, where the i n t e n s i t i e s a r e changing rap id ly with L,

Figure 7 i s included t o more c l ea r ly define the va r i a t ion i n

the regions of i n t e r e s t .

P

The morphology of these in t ens i ty var ia t ions , as shown

i n Figures 6 and 7, a t L > - 4.5, can t y p i c a l l y be described as

(1) a rapid i n i t i a l decrease i n the a t e n s i t i e s of these electrons,

which occurs i n the e a r l y phase of a geomagnetic disturbance, when

CK i s typ ica l ly > 20, followed by (2) a recovery phase i n which P

the i n t e n s i t i e s of these electrons increase t o approximately

those i n t e n s i t i e s which ex is ted pr ior t o the disturbance. The

durat ion of t he recovery i s seen to vary between - 1-2 days and

- 7-10 days, f o r various disturbances. The data f o r t he l a s t

week of May are exceptions t o t h i s t y p i c a l behavior i n t h a t a

recovery i s not observed a t L - 4-4.5 while it i s observed a t

-

L > 4.5.

22

Smaller geomagnetic disturbances, character ized by

CK < 20, appear t o be associated with gradual depletions of

these e lec t ron i n t e n s i t i e s a t L < - 4.5, as i s i l l u s t r a t e d by the

data f o r t he l a t te r pa r t s of February and April .

depletion-recovery cycle i s apparently s t i l l operative.

P

A t L = 6.0, the

For L 5 4 .O, examples of no observable depletions a re

evident a t the beginning of geomagnetic disturbances, p a r t i c u l a r l y

i n Figure 7, where the spread i n L i s reduced (e -g . , May 1 and

June 6, 1963). The temporal var ia t ions i n these f e w cases a r e

qui te s imi la r t o those observed f o r t he i n t e n s i t i e s of e lec t rons

(E > 40 keV) i n these regions of the outer zone.

During t h e f i r s t severa l months of observations, t he 213B

responses were s i g n i f i c a n t l y increased by t h e presence of

a r t i f i c i a l l y in jec ted high energy e lec t rons (see page 24 of t h e

t e x t ) . The primary mode of operation o f t h e Injun 3 s a t e l l i t e

during the f i rs t - 3 months of operation i s responsible f o r t h e

poor data sample obtained with t h i s de tec tor before - Apri l 1,

1963.

23

3 . The Temporal Variations of t he I n t e n s i t i e s of Electrons (E > 1.6 MeV)

I n Figure 8 a r e displayed the responses o f t he 302 G.M.

tube due t o the i n t e n s i t i e s of e lectrons (E > 1.6 MeV) a t low

a l t i t u d e s i n the outer zone f o r t he seven-month period under

invest igat ion. With t h e exception of t h e data fo r L = 3.0, and

the general monotonic decrease i n in t ens i t i e s superimposed on

the regular temporal var ia t ions a t L = 3.5, t he temporal varia-

t i ons of t he i n t e n s i t i e s of e lectrons (E > 1.6 MeV) trapped i n

the outer zone a r e of a form which vary i n magnitude from

10 t o Id, depending upon the pa r t i cu la r geomagnetic disturbance

and t h e value of L.

there is a rapid decrease i n the in t ens i t i e s of e lec t rons

(E > 1.6 MeV) which takes place within severa l days, followed

Associated with each geomagnetic disturbance

by a monotonic increase i n the i n t e n s i t i e s which continues u n t i l

e i t h e r another depletion occurs i n t he outer zone or the r a t e of

increase lessens and the i n t e n s i t i e s approach some "equilibrium"

l e v e l (e.g., a t L = 4.0 and 4.5 from - May 19 t o May 25) .

A t L = 3.0 and 3.5, the 3Ce responded pr imari ly t o

e lec t rons (E > 1.6 MeV) a r t i f i c i a l l y in j ec t ed i n t o the outer zone

. t

24

by the Soviet high a l t i t u d e nuclear detonations of October and

November, 1% [Frank, Van Allen, and H i l l s , 15641.

1963, the i n t e n s i t i e s were Jo (E > 1.6 MeV) = 4. - + 2 x 10

6 2 2 x 10

B = 0.20 - + 0.02 gauss.

B = 0.27 - + 0.02 gauss were reduced by a f ac to r of

i n t e n s i t i e s a t L = 3.0 exhibited an exponential time behavior

of t h e form exp (-t/-i) u n t i l about June 6, 1963, f o r which

T = 4.0 - f 5 days, throughout the period.

exponential decay which was interrupted during severa l l a rge

geomagnetic disturbances was observed a t L = 3.5 with

T = 45 - + 5 days.

On January 1,

and

a t L = 3.0 and 3.5, respect ively, f o r

A t L = 3.0 the i n t e n s i t i e s f o r

5

4 2 -1 (cm -sec)

4 . The

Unt i l May 8, 1963, an

Following a depletion, the time r a t e of change of the

i n t e n s i t i e s of e lectrons (E 3 1.6 MeV) was observed t o be constant

i n t i m e when the response of the 3@ G.M. tube was i n the l i nea r

region, and t o slowly decrease as the non-linear response region

was encountered. Making the correction f o r t he 302 G.M. tube

dead-time, it has been found tha t u n t i l t he "equilibrium"

i n t e n s i t i e s a re approa.ched, the time r a t e of change of the counting

r a t e of the 3@ is a "constant of t he geomagnetic disturbance",

depending only on the M A E K f o r the disturbance and the s t rength

of t h e magnetic f i e l d . That is, P

I .

25

dR Z = # ( B , M A X C K )

d t L P

following the i i t i a l deplet ion of the i n t e n s i t i s of e l ctrons

(E > 1.6 MeV).

disturbances a t L = 4.0 and B = 0.2 - + 0.2 gauss and i s presented

i n Figure 9.

event of mid-Septeniber 1963.

t h i s region of the outer zone, w i t h dR/dt decreasing by l e s s than

25% for an increase i n B of 0.1 gauss.

This quant i ty has been measured f o r t en geomagnetic

The datum for MAXCK = 48 was obtained from t h e P

The dependence on B i s weak f o r

I n Figure 10 the change i n dR/dt with L i s displayed fo r

t h e event of ea r ly July where M J Z K = 25. It can be seen t h a t

dR/dt increases very r ap id ly from - 0 t o near ly i t s m a x i m u m value

between L = 3.0 and 4..0, changes l i t t l e i n the hear t of the zone,

L = 4.5 - + 0.5, and then decreases with increasing L, though a t

a slower r a t e than on the inward s ide of the zone. Notice t h a t

t he counting r a t e s of t he 3@ f o r L 5 4.5, when extrapolated t o

in te rsec t ion , meet on Ju ly 6 which i s - 2 days sooner than the

extrapolated counting rates f o r L > 4.5.

rates appear t o be only slowly varying until t h a t t i m e .

preliminary survey of several other geomagnetic events ind ica tes

t h a t the slope of t he dR/dt vs M A Z K

throughout the region under invest igat ion.

P

These l a t t e r counting

A

l i n e i s independent of L P

26

Several cases of an apparent diffusion of e lec t rons

(E > 1.6 MeV) toward lower values of L have been observed i n

the Injun 3 3@ data. A t yp ica l observation is i l l u s t r a t e d

by the data presented i n the upper panelsof Figure 11 where a

set o f near ly iden t i ca l passes through the outer zone has been

se lec ted and the responses of t he 3CQ p lo t t ed against L.

Notice t h a t p r i o r t o onset of the geomagnetic disturbance the

peak i n the i n t e n s i t y of e lectrons (E > 1.6 MeV) occurred a t

L - 3.9, whereas following t h e i n i t i a l deplet ion and during

the period i n which t h e i n t e n s i t i e s were increasing, the maximum

occurred a t L - 4.5 - + 0.3, being a t higher L a t f i r s t and

progressively moving toward lower L.

ou ter zone i n t e n s i t y d i s t r ibu t ion i n l a t e Apri l (see Figure 1 4 ) ,

j u s t p r i o r t o a new disturbance, shows t h a t the peak i n the

i n t e n s i t i e s had progressed t o L - k.1, which i s the same behavior

exhibi ted during the previous month, pass 1 (March 31, revolut ion

134.1) being the l a s t of t he previous s e r i e s .

An observation of the

The motions of several secondary peaks i n the outer zone

e l ec t ron (E > 1.6 MeV) i n t e n s i t i e s were observed by the Injun 3

302 G.M. tube on May 18-19, 1963. The responses of t he 3Oe fo r

a l l ava i lab le outer zone passes during t h i s per iod a re p l o t t e d i n

27

Figure 12.

epochs (revolut ion 194-3-194.7 and 199-1957) secondary peaks a re

moving towards lower L with near ly constant i n t e n s i t i e s

2 a 7 x Id (cm -see)-’, when resolved from t h e contr ibut ion of

the quiescent outer zone in t ens i t i e s .

It can r ead i ly be seen tha t during two separate

From these and other s imilar observations, the low

a l t i t u d e inward ve loc i ty of the in t ens i ty m a x i m a of e lectrons

(E > 1.6 MeV) has been obtained between an L of - 3.5 and 6.5,

and a re presented i n Figure 13 along with the results of

Frank [1965b] f o r the leading edge of the d i s t r i b u t i o n of

e lec t rons (E > 1.6 MeV) observed near the geomagnetic equator.

The upper l i m i t of - 2 x

from Explorer 4. measurements [Van Allen, McIlwain, and Ludwig,

19591 of e lec t rons in jec ted i n t o the magnetosphere during the

Argus p ro jec t .

and - 2 L (day)

d i f fe rence between these r e s u l t s and those of Frank suggest

t h a t the leading edge of such a d is t r ibu t ion , from which the

da ta of Frank were obtained, moves a t a l a rge r ve loc i ty than

t h e peak of t h e d i s t r ibu t ion , which i s the region of i n t e r e s t

i n these observations.

-

L (day)-l a t L = 2.1 was obtained

The observed r a t e s a t L = 4 and 6 are - -1 , respect ively. The order of magnitude

28

4. Outer Zone Low Alt i tude Prof i les

Return now t o Figure 11, which presents t he responses of

213A, 213B, and 302 f o r a s e t of nearly i d e n t i c a l passes through

the outer zone during the disturbance beginning Apr i l 4 , 1963

( W K P = 33 on Apr i l 5 ) .

of e lec t rons (E > 1.6 MeV) were grea t ly reduced above L - 3.5

by Apr i l 5, and during the following s i x days were observed t o

s t e a d i l y increase toward pre-dis turbance i n t e n s i t i e s of

- 2 x 10

gress ive ly towards lower L. The i n t e n s i t i e s o f e lec t rons

(E > 230 keV) decreased during a small disturbance on April 1,

and were not g r e a t l y enhanced until after the Apr i l 4 onset a t

which time they increased rapidly. The i n t e n s i t i e s of e lec t rons

(E > 40 keV) displayed la rge s p a t i a l and temporal var ia t ions

dur ing Apri l 4-6 when CK > 20 as compared t o t h e i n t e n s i t i e s

of Apri l 2 , which represents a quiet t i m e p r o f i l e . The sharp

terminations of t he i n t e n s i t i e s o f e lec t rons (E > 40 keV) a t

L - 6.3 and - 5.8 on Apri l 4 and 6, respect ively, ind ica te t h a t

high l a t i t u d e trapping boundary f o r these electrons, which i s

t y p i c a l l y above L - 8 [Frank, Van Allen, and Craven, 19641, i s

As already discussed, t h e i n t e n s i t i e s

4 2 -1 (cm -see) , the maximum i n i n t e n s i t i e s moving pro-

P

.

temporarily displaced towards lower l a t i t udes during geomagnet-

i c a l l y disturbed periods. The duration of the displacement and

i t s m a x i m u m magnitude cannot be obtained from t h i s data .

Another set of outer zone p ro f i l e s is presented i n

Figure 14. f o r the period Apr i l 28 t o May 4, 1963, during which

a disturbance with MAXCK = 33 (May 1) began on April 30. O f

i n t e r e s t a re the p r o f i l e s of the l o w a l t i t u d e outer zone

i n t e n s i t i e s o f e lec t rons (E > 4.0 keV, > 230 keV, > 1.6 MeV) on

May 1, 1963, a t - 0239 U.T. a s observed during the southbound

por t ion of revolution 1726 over North America. It i s r ead i ly

seen t h a t the i n t e n s i t i e s o f these e lec t rons a r e ca tas t rophica l ly

depleted throughout the outer zone with t h e i n t e n s i t i e s of

P

e lec t rons (E > 1.6 MeV) being markedly depleted above L - 3.5,

above L - 4.0 for e lectrons (E > 230 keV) and above L - 4.6

f o r e lec t rons ( E > 40 keV). The low a l t i t u d e e l ec t ron i n t e n s i t i e s

a t L = 5.0 on May 1, 1963, a t - (237 U.T. were

2 -1 j

j

J

(E > 4.0 keV) - 740 (cm -see-sr)

( E > 230 keV) < 250 (cm -sec-sr)-’

(E > 1.6 MeV) - 20 (cm -see)-’

L

2 I

2 0

The data from t h e northbound port ion of revolut ion 1726

which passed through the outer zone a t - Q25 U.T. indicate

t h a t t he i n t e n s i t i e s of e lectrons (E > 230 keV,> 1.6 MeV) were

g r e a t l y depleted down t o L - 4.4 and L - 4, respect ively, a t

low a l t i tudes , andthe i n t e n s i t i e s of e lec t rons (E > 4.0 keV)

were g rea t e r than - 2 x 10 4 2 -1 ( c m -sec-sr) below L - 7.5 and

then decreased abruptly by over t w o orders of magnitude. The

displaced high l a t i t u d e trapping boundary f o r e lec t rons

( E > 4.0 keV) was observed a t a l oca l time of - 1320 during the

northbound pass and a t - 1830 during the southbound pass . The

corresponding median pos i t ions of the boundary [Frank e t a l . ,

1964.1, as defined by the value of L f o r which j (E > 40 keV) A

3 2 -1 (cm -see-sr) decreases below 3 x 10 were - 18 and - 10,

respect ively, ind ica t ing t h a t a t -1320 l o c a l time the boundary

was displaced by hL - 10 and a t - 1830 by AL - 5.5.

The hourly scal ings of the horizontal component of t he

geomagnetic f i e l d a t S ik ta (L - 4.) and College (L -., 5.5), Alaska

show abrupt increases of - 100 7 and - 200 7 , respect ively,

occurred during t h e hour 0200-0300 U.T. o f May 1, 1963, as

compared t o the hourly scal ings f o r t he previous few hours.

On the southbound pass of revolut ion 1726, Injun 3 was a t west

longitude 1 2 7 O when it crossed the L = 5.5 s h e l l a t an a l t i t u d e

of - 2000 km, thus being within - 20" of longitude of College.

College riometer data [courtesy of R . Parthasarathy, Geophysical

I n s t i t u t e , University of Alaska, College, Alaska] ind ica tes

t h a t cosmic rad io noise absorption a t 27.6-Mc/s was minimum

during the period 2200 U.T. April 30 t o O9OO U.T. May 1, 1963,

and was ce r t a in ly never grea te r than 0.4. db above the quie t t i m e

background Leinbach, p r iva t e communication] .

5 . Maximum Resolution of Outer Zone Electron I n t e n s i t i e s During Geomagnetic Disturbances

The observation of outer zone depletion of t h e i n t e n s i t i e s

of e lectrons (E > 40 keV, > 230 keV, > 1.6 MeV) and the simul-

taneous increase i n the horizontal component of the geomagnetic

f i e l d suggests an attempt t o cor re la te the time behavior of the

geomagnetic f i e l d and the outer zone e lec t ron i n t e n s i t i e s on a

scale of - 2 hours, t h a t being the o r b i t a l period of Injun 3 .

For t h e periods of March 28-April 12 and June 4-10 a l l ava i lab le

da ta a t L = 4..0 + 0.1 and .l7 < - - B < .37 gauss have been p lo t t ed

aga ins t time and a re displayed i n Figure 15, along with the

-

corresponding 3-hour values of K and the 3-hour averages of the P

32

horizontal component o f t he geomagnetic f i e l d a t College,

Alaska. The temporal var ia t ions of t h e i n t e n s i t i e s of e lec t rons

(E > 4.0 keV, > 230 keV, > 1.6 MeV) are cons is ten t with the

heretofore presented data . The i n t e n s i t i e s o f e lectrons

( E > 4.0 keV), while not being observed t o decrease a t onset,

do increase as expected, and appear t o do so i n assoc ia t ion

with each increase i n the horizontal component of the order of

100 7 or grea te r . The i n t e n s i t i e s of e lec t rons ( E > 230 keV)

a re observed t o gradually decrease near the onset of t h e Apr i l

event and t o be replenished within - 36 hours a f t e r m a x i m u m

deplet ion. No depletion i s observed i n t he June event, and

the increase i n i n t e n s i t i e s occurs within - 10 hours. The la rge

depletions i n t h e i n t e n s i t i e s of e lectrons (E > 1.6 MeV) a re

c l e a r l y defined, as a re the steady increases i n i n t e n s i t i e s

following the depletion. The large depletions a re observed t o

take place within 3-6 hours.

33

V. Discussion and Summary

The temporal var ia t ions of trapped outer zone electrons

(E > 40 keV, > 230 keV, > 1.6 MeV) which mirror a t low a l t i t u d e s

have been studied during the period from January 1 t o Ju ly 31,

1963, with the U . of Iowa/ONR research s a t e l l i t e Injun 3. The

unid i rec t iona l i n t e n s i t i e s of e lectrons (E > 40 keV) which mirror

a t low a l t i t u d e s (- 1500 km) have been d i r e c t l y compared with

the omnidirectional i n t e n s i t i e s of these electrons near t he

geomagnetic equator ia l plane [Frank, Van Allen, and H i l l s , 19641

a t L - 4, and it has been found that , t o within a f ac to r of 2,

the two a re c lose ly r e l a t e d throughout the range of observed

i n t e n s i t i e s , regardless of geomagnetic conditions a t the times

of t he measurements. The medians o f t he r a t i o s of t he equator ia l

omnidirectional i n t e n s i t i e s t o the low a l t i t u d e unid i rec t iona l

i n t e n s i t i e s f o r j 4 (E > 40 keV) - 7.5 2 2.5 x 10 and

I 12 2 4 x 10 5 2 (cm -sec-sr)-’, a r e 32 and 14, respect ively,

ind ica t ing an approach t o equal omnidirectional i n t e n s i t i e s 2 -1

along the f i e l d l i n e s as the i n t e n s i t i e s approach - 107-8 (cm -see) . That t h e i n t e n s i t i e s a t low a l t i t udes (- 1500 km) approach isotropy

over a t l e a s t - 3rr i n t h i s i n t ens i ty l i m i t i s c l e a r l y demonstrated

a t L - 5.5 i n Figure 4 of Parthasarathy, Bekery, and

Venketesan 119651, i n which Injun 3 data were used t o compare

the unidirect ional i n t ens i t i e s of electrons (E > 4.0 keV)

mirroring a t - 1500 km with those whose p i t ch angles a t

- 1500 lan are < 40°, and hence a par t of which are absorbed

i n t h e upper atmosphere [cf. O'Brien, 19641. Equal omnidirec-

t i o n a l i n t ens i t i e s along a f i e l d line,extending from - 1500 km

t o t h e geomagnetic equator ia l plane, and isotropy a t - 1500 km

folluw from isotropy near the geomagnetic equator ia l plane

[Ray, 19591.

f i e l d l i n e s with only one minimum in B and an angular d i s t r ibu-

t i o n which i s wel l behaved along t h e f i e l d l i ne , it i s probably

a good approximation.

While the converse c l ea r ly need not follow, f o r

The in t ens i t i e s of outer zone electrons (E > 40 keV)

have been observed t o change abruptly a t t he onset of geomagnetic

disturbances [ c f . Frank, Van Allen, and H i l l s , 19641.

events have been observed when the in t ens i ty changes occurred

wi th in the same 3-6 hour periods as the horizontal component

of t h e geomagnetic f i e l d a t College, Alaska (L - 5.5) increased

by 100-200 7 . A n observation of a catastrophic decrease i n the

i n t e n s i t i e s of these electrons i n the outer zone down t o L - 4.5

on May 1, 1963, a t - 0230 U.T., during the same - 1 hour period

Several

35

i n which the horizontal component a t S i tka (L - 4) and College,

Alaska, increased by - 100 7 and - 200 7 , respect ively, has

been presented.

(E > 40 keV) were - 740 ( cm -sec-sr)-’ a t L - 5 , which were a

f ac to r of - 1000 less than t h e quiet t i m e i n t e n s i t i e s t y p i c a l l y

observed.

higher energies . Several s imilar types of depletion have s ince

been found i n t h e data, again occurring i n the same time periods

i n which t h e horizontal component a t College had increased by

> 100 y above the t y p i c a l qu ie t time values.

these depletions were ce r t a in ly less than - 4-6 hours f o r

e lec t rons (E > 40 keV), as they were not observed during the

next ava i lab le transits through the outer zone.

are required i n order t o ascer ta in whether or not t h i s phenomenon

occurs f requent ly a t t he beginning of geomagnetic disturbances.

A t t h i s t i m e t h e i n t e n s i t i e s of e lec t rons

2

This la rge scale depletion was a l s o observed a t t he

The durations of

Further s tud ies

It has been shown t h a t during each geomagnetically

dis turbed period an enhancement i n t he i n t e n s i t i e s of e lec t rons

(E > 40 keV) takes place throughout the outer zone [ c f . Frank e t a l . ,

19643, and t h a t t h e increase, when averaged over the region

3.5 < L < 5.0 is an increasing function of MAXCK

turbances character ized by MAXCK 5 15, the changes i n the

For d i s - P - -

P

i n t e n s i t i e s a r e only marginally observable, while f o r disturbances

with MAXCK > 35 the increases become l e s s s ens i t i ve t o t h e

parameter, indicat ing an asymptotic approach t o an upper l i m i t

f o r t h e i n t e n s i t i e s of durably trapped e lec t rons (E > 40 keV).

P "

This upper l i m i t ,

comparable t o the

i n t e n s i t i e s along

Jo (E > 40 keV) - 7 2 5 x 10 7 2 (cm -sec)-', i s

i n t e n s i t i e s required f o r equal omnidirectional

the f i e l d l i n e s a t L - 4. and compares favorably

with the upper l i m i t s f o r durably trapped e lec t rons (E > 40 keV)

computed by Kennel and Petschek [l965] due t o whis t le r mode

noise d i f fus ion of p i t c h angles f o r these electrons. These

l i m i t s were Jo (E > 4.0 keV) - 2 x 10 8 2 -1 (cm -sec) a t L - 4 and

7 2 -1 (cm -sec) - 4. x 10 a t L - 6, with an increasing d iurna l

e f f e c t occurring f o r L 2 5 .

During periods of geomagnetic calm (ZK < 15), which P

followed dis turbed periods when large enhancements i n t h e

i n t e n s i t i e s of e lec t rons (E > 40 keV) occurred, t h e i n t e n s i t i e s

of these e lec t rons were observed t o decrease i n approximately an

exponential manner.

exp ( - t /~ ) , T has been found t o vary between 2 .0 and 6.5 days

For a representat ion proportional t o

for 3 . 5 5 L 5 6.0, with an average of k.2 days, f o r four post-

dis turbance per iods. A t L = 3.0 t he decay constant had

37

increased s ign i f i can t ly , t o I 2 - + 3 days.

Injun 3 and Explorer 14 measurements a t L - 4 , f o r t he four

A comparison of *

periods, has shown the decay constants t o be very s imi la r a t

low a l t i t u d e s and large r a d i a l distances, t he average values

of T being 4 and 3.8 days, respect ively.

"he i n t e n s i t i e s of e lec t rons (E > 1.6 MeV) have a l so been

shown t o vary g rea t ly a t the onset of geomagnetic disturbances

[ c f . Frank, Van Allen, and H i l l s , 1964.1 . During the few hours

i n which t h e i n t e n s i t i e s of e lectrons (E > 40 keV) were observed

t o change abruptly, t he i n t e n s i t i e s of e lec t rons (E > 1.6 MeV)

were observed t o decrease by fac tors of 10-12 i n the outer

zone, and i n t he following 5-10 days t o increase l i n e a r l y with

t i m e , provided CK

recovery.

did not increase above - 10 during the P

The depth t o which depletion occurred i n the outer

zone was dependent upon the i n t e n s i t y of t h e disturbance, a s

indicated by MAZKp. For small disturbances (MAXCK < 20),

only deplet ions and/or an end t o enhancements would occur below P

L = 4.5, but a t higher L s t r i k i n g depletions were evident.

Only the more intense disturbances, which were character ized

by MAXCK > 30, produced l a rge scale depletions a t L < N 4..0. P -

The r a t e of increase i n the in t ens i t i e s of e lectrons

(E > 1.6 MeV) following depletion was shown t o be an increasing

function of the MA3ZK which characterizes the disturbance, and

a t L = 4. was 10 (cm -see-day) and 7 x 10 (cm -see-day) f o r

MAXCK It appears t h a t the slope of

t h i s l i n e i s independent of L f o r the region under invest igat ion.

For a given W E K however, the magnitude of t h e r a t e of

increase i s a maximum i n the hear t of t h e outer zone, L - 4-4.5,

and decreases a t higher and lower L, the decrease being more

rap id a t lower L. Enhancement appears t o begin e a r l i e r a t lower

L, with a t i m e delay of as much as two days between L - 4 and

L = 5-6. The observations of abnormally low i n t e n s i t i e s of

e lec t rons (E > 1.6 MeV) a t low a l t i tudes i n the outer zone from

2 mid-December, 1964 t o e a r l y February, 1965 ( typ ica l ly < 5 x 10

(cm -see) ) as observed by Injun 4 [Frank, Van Allen, Craven,

and H i l l s , 19651 are qui te normal when considered i n l i g h t of

these Injun 3 observations, as some s i x small geomagnetic

disturbances, fo r which 10 < M A E K 5 25, occurred i n t h i s

period, but no la rge sca le disturbances were observable.

P’ 3 2 -1 4 2 -1

= 23 and 48, respect ively. P

P’

2 -1

P -

39

Wentworth [1$41 has reported t h a t f o r some 25 geo-

magnetic disturbances which occurred between August 1, 1960,

and June 16, 1963, f o r which MAXCK > 30 and f o r which no P -

disturbances occurred i n t h e preceding 7 days o r i n the following

11 days, hydromagnetic emissions were more l i k e l y t o occur

during the seven days a f t e r CK

the geomagnetically quiet per iods.

f i r s t went above 30 then during P

The observations of apparent inward d i f fus ion of e lec t rons

(E > 1.6 MeV) and of protons (40 < E < 110 MeV) near the geomagnetic

equator ia l plane have been reported, respect ively, by Frank [ 19651

a t L - 3-5 and McIlwain [ 19651 a t L = 2.2.

have been made a t low a l t i t u d e s f o r 3.5 < L < 6.5 with Injun 3

y ie ld ing apparent d i f fus ion r a t e s of - 10 L (day) and

- 2 L (day)-’ a t L = 4 .O and 6.0, respect ively, f o r e lec t rons

(E > 1.6 MeV).

observed near the geomagnetic equator ia l plane by Frank, indicat ing

t h a t the leading edge of t h e d is t r ibu t ion , from which t h e calcula-

t i ons of Frank were obtained, moves a t a l a rge r ve loc i ty than the

peak of t h e d i s t r ibu t ion , which i s the region of i n t e r e s t i n these

Similar observations

-2 -1

These r a t e s a re a f ac to r of 10 lower than those

observations.

4.0

On January 1, 1963, the observed i n t e n s i t i e s of e lec t rons

(E > 1.6 MeV) which were a r t i f i c i a l l y in jec ted i n t o the magneto-

sphere by the Soviet nuclear bu r s t s i n October and November,

4 2 - 1962 were Jo (E > 1.6 MeV) = 4. + 2 x 10 5 and 6 + 2 x 10 (cm -sec)-' - a t L = 3.0 and 3.5, respectively, and B = 0.2 - + 0.02 gauss.

L = 3.0 the i n t e n s i t i e s decreased exponentially with a decay

constant T = 4.0 - + 5 days u n t i l Ju ly 7, 1963.

a t L = 3.5 general ly decreased w i t h T = 45 - + 5 days u n t i l May 8,

1963, but were g rea t ly modulated several times during la rge

geomagnetic disturbances.

B = 0.27 - + 0.m gauss were a fac tor of four l e s s than those a t

B = 0.20 - + 0.02 gauss.

i n good agreement with those observed by Van Allen [19641 a t

these L values with Explorer 1 4 .

A t

The i n t e n s i t i e s

The i n t e n s i t i e s a t L = 3.0 and

The values of these decay constants a r e

The i n t e n s i t i e s of e lectrons ( E > 230 keV) have been

found t o vary i n a systematic manner, as did the heretofore

discussed cases.

with each geomagnetically disturbed period the i n t e n s i t i e s of

e lec t rons (E > 230 keV) exhib i t an i n i t i a l decrease, followed

by an enhancement phase which l a s t s from 1-2 t o 7-10 days, during

For L > 4.5, i t is typ ica l ly observed t h a t -

41

which near predisturbance i n t e n s i t i e s a re re-establ ished and

fur ther enhancement does not occur.

W K < 20, generally cause only small depletions w i t h no

observable enhancements f ollawing, while a t l a rger L these

var ia t ions a re discernible i n the data. During severa l more

intense disturbances, f o r which MAXCK

these e lec t ron i n t e n s i t i e s below L - 4.5 within 6-8 hours, with

no observable depletions preceding the increases, were observed,

which suggests t h a t the mechanisms by which - 4.0 keV e lec t rons

a re accelerated, may, during the more intense disturbances, be

operative on such a sca le as t o energize electrons t o energies

of t h e order of .., 300 keV. The more gradual enhancements, which

a re more cha rac t e r i s t i c of the in t ens i t i e s a t L > 4 , a r e s imi la r

i n form t o those observed f o r t he i n t e n s i t i e s of e lec t rons

(E > 1.6 MeV).

For L <, 4, weak disturbances

P

>_ 28, rapid increases i n P

Although the 27-day per iodic i ty i n outer zone e lec t ron

( E > 280 keV, > 1.2 MeV) i n t ens i t i e s recent ly discussed by Williams

119661 is c l e a r l y expected from e a r l i e r r e s u l t s [ c f . Forbush e t a l . ,

1962; Frank, Van Allen, and H i l l s , 19641, i t s assoc ia t ion with

t h e passages of t h e interplanetary magnetic f i e l d sec tor boundaries

[Ness and Wilcox, 19651 and several so l a r wind parameters i s of

g r e a t importance.

I wish t o express my s incere thanks t o D r . L. A . Frank

f o r t h e suggestions which prompted th i s work and f o r many

valuable discussions during the course of t he work. The continued

i n t e r e s t and he lp fu l suggestions offered by D r . J. A . Van Allen

are g r a t e f u l l y acknowledged. M r . R . J . DeCoster's ass i s tance

with the numerical integrat ions and t h e graphing of the data was

invaluable. The research was supported i n large p a r t by the

Off ice of Naval Research under contracts Ngonr 93803 and

Nom 1509(06).

REFERENCES

Axford, W. I., The in te rac t ion between the solar wind and the

ear th’s magnetosphere, J. Geophys. Res . , a, 3791-3796,

1962. Davis, L. R. , Jr., and D. B. Chang, On the e f f ec t of geomagnetic

f luctuat ions on trapped par t ic les , J. Geophys . Res., g, 2169-2179, 1962.

Forbush, S . E. , D. Venkatesan, and C. E . McIlwain, In t ens i ty

var ia t ions i n outer Van Allen radiat ion b e l t , J. Geophys.

Res . , 66, 2275-2287, 1961.

Forbush, S. E., G. Pizzel la , and D. Venkatesan, The morphology

and temporal var ia t ions of the Van Allen rad ia t ion b e l t ,

October 1959 t o December 1960, J. Geophys. Res., -7 67

3651-3668, I$@..

Frank, L . A . , Efficiency o f a Geiger-Mueller tube f o r non-

penetrating electrons, J. Franklin I n s t i t u t e , Q, 91-106,

1962. Frank, L. A . , A survey of electrons E > 4.0 keV beyond 5 ear th

r a d i i with Explorer 14, J. Geophys. Res ., 70, 1593-1626,

196%. -

44.

Frank, L . A . , Inward r ad ia l diffusion of electrons greater

than 1.6 mill ion electron volts i n the outer radiat ion

zone, J. Geophys. R e s . , 70, 3533-3540, l965b.

Frank, L. A . , and J. A . Van Allen, Measurements o f energetic

e lectrons i n t h e v i c i n i t y of the sunward magnetospheric

boundary with Explorer 1 4 , J. Geophys. Res., - 69, 493-4.932,

1964..

Frank, L. A . , J . A . Van Allen, and J. D. Craven, Large diurnal

var ia t ions of gecmagnetically trapped and of prec ip i ta ted

electrons observed a t low al t i tudes, J. Geophys. Res.,

2, 3155-3167, 15@+.

Frank, L. A . , J . A. Van Allen, and H. K. H i l l s , A study of

charged pa r t i c l e s i n the ear th ' s outer rad ia t ion zone

with Explorer 14., J. Geophys. R e s . , - 69, 2171-2191, 1964 .

Frank, L. A . , J . A . Van Allen, W . A . Whelpley, and J. D. Craven,

Absolute in t ens i t i e s of geomagnetically trapped pa r t i c l e s

with Explorer 14, J. Geophys. Res., - 68, 1573-1579, 1963.

Frank, L. A . , J. A . Van Allen, J. D. Craven, and H. K. H i l l s ,

Measurements of low-energy charged p a r t i c l e i n t ens i t i e s

a t l o w a l t i t udes with Injun 4, Trans. Am. Geophys. Union,

- 46, 140, 1965 (abs t rac t ) .

. 45

Freeman, J . W., Jr., The morphology o f t h e e lec t ron d i s t r i b u t i o n

i n the outer rad ia t ion zone and near the magnetospheric

boundary a s observed by Explorer 12, J. Geophys. Res.,

- 69, 1691-1723, 1964..

Freeman, J. W . , J. A. Van Allen, and L. J. Cahill, Jr., Explorer 12

observations of t h e magnetospheric boundary and the

associated so la r plasma on September 13, 1961, J. Geophys.

.f Res 68, 2Ul-2130, 1963.

F r i t z , T. A., The passive magnetic or ien ta t ion of s a t e l l i t e

Injun -3, U. of Iowa Research Report 65-21, 1965 (unpublished).

Herlofson, N., Diffusion of pa r t i c l e s i n the e a r t h ' s r ad ia t ion

b e l t s , Phys. Rev. Le t te rs , 2, 4.14-4.16, 1960.

Kellogg, P. J., Van Allen rad ia t ion of so l a r or igin, Nature (London),

- 183, 1295-1297, 1959.

Kennel, C. F., and H. E. Petschek, A l i m i t on s t ab ly trapped

p a r t i c l e fluxes, Avco Everett Research Laboratory Research

Report 219, 1965. - Lincoln, J. V., Geomagnetic and solar data, J. Geophys. Res. ,

- 68, 1963.

4.6

McIlwain, C . E . , Coordinates f o r mapping the d i s t r ibu t ion of

magnetically trapped pa r t i c l e s , J. Geophys. Res ., 66,

3681-3692, 1-961- McIlwain, C . E., Long-term changes i n the d i s t r ibu t ion of t h e

40- t o 110-MeV trapped protons, Trans. Am. Geophys.

- - Union, 46, 1 4 1 , 1965 ( abs t r ac t ) .

Nakada, M. P., J. W. Dungey, and W . N . Hess, Theoretical s tud ies

of protons i n the outer rad ia t ion b e l t , Goddard Space

F l ight Center Research Repor t X-640-64 -110, 1964.

Ness, N. F., and J. M. Wilcox, Sector s t ruc tu re of t h e quie t

in te rp lane tary magnetic f i e ld , Science, 148, 1592-1594, 1965

Northrop, T. G. , and Edward Teller, S t a b i l i t y o f t he adiabat ic

motion of charged p a r t i c l e s i n the e a r t h ' s f i e l d , Phys.

4, Rev - 117, 215-225, 1960.

O'Brien, B. J., High-lati tude geophysical s tud ies with s a t e l l i t e

Injun 3, Par t 3:

atmosphere, J. Geophys. Res., @, 13-43, 1964.

Prec ip i ta t ion of e lec t rons i n t o the

O'Brien, B. J., C . D. Laughlin, and D. A. Gurnett, High-latitude

geophysical s tudies with s a t e l l i t e Injun 3, Par t 1:

Description of the s a t e l l i t e , J. Geophys. Res., 69, 1-12,

1964 .

47

Parker, E. N . , Geomagnetic f luctuat ions and the form of t he

outer zone o f the Van Allen radiat ion b e l t , J . Geophys . -7 Res 65, 3117-3130, 1960.

Parthasarathy, R. , High l a t i t u d e geophysical data , U. of Alaska

Report UAG-C 32, 1963.

Parthasarathy, R. , F. T . Berkey, and D . Venkatesan, Auroral

zone e lec t ron f lux and i t s r e l a t ion t o broadbeam radio-

wave absorption, U . of Alaska Research Report UAG-Rl68,

1965

Pizze l la , G. , C. E . McIlwain, and J. A. Van Allen, Time var ia-

t ions of i n t e n s i t i e s i n t h e e a r t h ' s inner rad ia t ion zone,

October 1959 through December 1960, J. Geophys. Res.,

a, 1235-1253, 1962. Ray, E . C . , On the appl icat ion of L iouv i l l e ' s theorem t o t he

i n t e n s i t i e s of r ad ia t ion trapped i n the geomagnetic

f i e l d , University of Iowa Research Report 59-21, 1959

(unpublished) . Serbu, G . P., Results f rom the IMP-I retarding po ten t i a l

analyzer, Space Research V, North-Holland Publishing

Company, Amsterdam, 564 -574, 1965.

4.8

Snyder, C . W . , M . Neugebauer, and U. R. Rao, The so la r wind

ve loc i ty and i t s cor re la t ion with cosmic r ay var ia t ions

and with so l a r and geomagnetic a c t i v i t y , J. Geophys.

Res., 68, - 6361-6370, 1963.

Speiser, T. W. , P a r t i c l e t r a j ec to r i e s i n a model current sheet ,

based on the open model of the magnetosphere, w i t h

appl icat ions t o aurora l pa r t i c l e s , J. Geophys . Res.,

E, 1717-17283 1965.

Taylor, H. E. , and E . W . Hones, Adiabatic motion of aurora l

p a r t i c l e s i n a model of the e l e c t r i c and magnetic f i e l d s

surrounding the ear th , J. Geophys. Res., - 70, 3605-3628,

1965

Van Allen, J. A., Dynamics, composition and or ig in of geomagneti-

c a l l y trapped corpuscular rad ia t ion , P a n s . In te rn .

htronom. Union, 11~, 99-136, 1%. - Van Allen, J. A . , Lifetimes of geomagnetically trapped e lec t rons

of severa l MeV energy, Nature (London), - 203, lOO6-lOO7, 1%. . Van Allen, J. A . , C . E. McIlwain, and G . H. Ludwig, S a t e l l i t e

observations of e lectrons a r t i f i c i a l l y in jec ted i n t o the

geomagnetic f i e l d , J. Geophys. Res ., - 64., 877-891, 1959.

49

Van Allen, J. A., and S. M. Krimigis, Impulsive emission of

- 4.0 keV electrons from the sun, J. Geophys. R e s . , 2,

5737-5751, 1965 - Wentworth, R. C., Enhancement of hydromagnetic emissions a f t e r

geomagnetic storms, J. Geophys. R e s . , 69, 229-2298,

1964.

Williams, D. J., A 27-day per iodici ty i n outer zone trapped

electron in t ens i t i e s , J. Geophys . Res., z, 1815-1826,

1966.

W i l l i a m s , D. J., and A. M. Smith, Daytime trapped electron

in t ens i t i e s a t high la t i tudes a t 1100 kilometers,

J. Geophys. Res., E, 541-556, 1965.

TABLE I

1.2 mica

Physical Parameters of Several

Injun 3 Geiger-Mueller Tubes

1.2 mica 48 aluminum

Designation

Axis of Viewing Cone with Respect t o 5

~~~

Half-Angle of Viewing Cone

Shielding Window (mg-cm-2)

Minimum Penetration Energy (MeV)

Window

Wall

Geometric Factor f o r Penetrat ing P a r t i c l e s

Direct ional (cn?-sr>

Omnidirectional ( em2

2 1 3 A 2 13B

perpendicular

1 3 O

1

2.2 lead 0.56 magnesium

E - 0.04. e

P E - 0.5

Ee cu 0.23

E - 5 P

E - 8 E - 4.0

e

P

6 x lo-’* -F 5 x 10

- 0.2

Omnidirectional over - 3rr

0.4 s t a i n l e s s s t e e l 0.265 magnesium

---

E - 1.6 E - 23 e

P

0.6*

* See pages 8-10 of t e x t .

1

2

3

4.

5

6

0.03

3

0.03

2

0.03

2

0.03

0.07

0.03

0.02

0.03

0.02

0.06

5 0.2

11

0.05 3

0.04.

2 -5

0.04. 0.2

0.07

5

0.05 3

0.05

2.5

TABLE I1

Energies (MeV) Above Which the Relative Contributions t o the

Counting Rates of Several Injun 3 Geiger-Mueller Tubes a re Cy,

f o r a D i f f e ren t i a l Number-Energy Spectrum of the Form AI?,-’.

Detect or Designa-

t i o n 0.5 0.3 0.1

0.6

22

2 1 3 A 302

2

$3 6

76

2 1 3 A 3@

0.1

7

0.2

E 0.5

26

2 1 3 A 302

0.06

4. 0.08

6 0.17 9

2 1 3 ~ 302

0.06

3

0.07

4 - 5

0.09

6.5

2 1 3 A

302 0.08

0.3 0 * 055 0.09

0.055 0.12

2 1 3 A 3@

0.05

0.07

0.07

0.13

52

TABLE I11

Decay Constants f o r the I n t e n s i t i e s

of Electrons (E > 40 keV) a t L - 4

EWCH

(1963) -

February 14-24.

March 10-25

May 14-24

July 7-16

Average

INJUN 3

T - + 1.0 Days

4 .O

6.5

2 - 5

3.0

4.. 0

4.5'

4..5

4.. 0

2 .o

3-75

. .

53

FIGURE CAPTIONS

Figure 1. The ef f ic ienc ies of several Injun 3 Geiger-Mueller

tubes as a funct ion of e lectron energy.

Figure 2. The responses of t h e Injun 3 213A G.M. tube due t o

the i n t e n s i t i e s of e lectrons (E > 4 0 keV) trapped i n the

outer rad ia t ion zone and mirroring a t low a l t i t udes ,

selected a t L = 3.0, 3.5, 4.0, 4.5, 5.0, and 6.0 - + 0.1

t o display the temporal var ia t ions during the period

from January 1 t o Ju ly 31, 1963.

defined there in .

The values of B a r e

Figure 3 . The averaged increase i n the i n t e n s i t i e s of e lectrons

(E > 40 keV) trapped i n the outer zone and mirroring a t

low a l t i t u d e s a t t h e onset o? a geomagnetic disturbance

as a funct ion of the maximum CK occurring during the

disturbance. The average is taken over t he i n t e n s i t i e s

measured by the In jun 3 213A G.M. tube a t L = 3.5, 4.0,

4.5, and 5.0 - + 0.1.

P

I . 54

Figure 4 . The observed decay constants, T , f o r the i n t e n s i t i e s

. of electrons (E > 40 keV) trapped i n the outer zone and

mirroring a t low a l t i t udes , as measured by the Injun 3

2 1 3 A G.M. tube as a funct ion o f L, when the i n t e n s i t i e s

a re represented by j (E > 40 keV, t ) = j (E > 40 keV, t = 0)

exp ( - t / T ) , for four periods of l a w K following geomagneti-

c a l l y disturbed periods. P

Figure 5. The near ly simultaneous observations of the unid i rec t iona l

i n t e n s i t i e s of e lectrons ( E > 40 keV) trapped a t low

a l t i t udes i n the outer zone with Injun 3 a t L = 4 .O - + 0.1

and the corresponding omnidirectional i n t e n s i t i e s near

the geomagnetic equator ia l plane with Explorer 1 4 a t

L = 4.2 - + 0.05.

within - 24 hours.

The measurements a re simultaneous t o

Figure 6. A continuation of Figure 2 f o r the responses of t he

213B G.M. tube due t o t h e i n t e n s i t i e s of e lectrons

(E > 230 keV).

55

Figure 7. The responses o f the Injun 3 213B G.M. tube due t o t he

i n t e n s i t i e s of e lectrons (E > 230 keV) trapped i n t h e outer

r ad ia t ion zone and mirroring a t low a l t i t u d e s , a t

L = 5.0 - + 0.1 and 3.95 - + 0.05 during the period from

May 1 t o Ju ly 31, 1963. The d i f f e r e n t temporal behavior

a t the two values of L i s c lear ly displayed.

Figure 8. A continuation of Figure 2 f o r t he responses of the

3Q G.M. tube due t o the i n t e n s i t i e s of e lec t rons

(E > 1.6 MeV).

Figure 9. The time r a t e of change of t h e response of t h e Injun 3

3@ G.M. tube due t o the in t ens i t i e s of e lec t rons

(E > 1.6 MeV) a t L = 4.0 - + 1.0 following the depletion of

i n t e n s i t i e s a t t h e onset of a geomagnetic disturbance as

a funct ion of the maximum CK

disturbance . occurring during the

P

Figure 10. An example of the l i nea r increases i n t i m e o f the

responses of t he 3@ G.M. tube due t o the i n t e n s i t i e s of

e l ec t rons (E > 1.6 MeV) a t low a l t i t u d e s i n the outer zone

following the i n i t i a l depletion phase. The disturbance was

character ized by W K p = 25.

56

Figure 11. A s e t of near ly iden t i ca l passes through the outer

zone between March 31 and April 12, 1963, which i l l u s t r a t e s

the s p a t i a l and temporal changes which occur i n the

i n t e n s i t i e s of e lec t rons (E > 4.0 keV, > 230 keV, > 1.6 MeV)

during a typ ica l geomagnetic disturbance. The inward

motion of the maximum response of the 3@ is an ind ica t ion

of t r ans -L diffusion.

Figure 12. A set of consecutive outer zone p ro f i l e s which

demonstrates t he inward motions of several secondary msxima

of the i n t e n s i t i e s of e lectrons (E > 1.6 MeV) during May 18

and 19, 1963.

Figure 13. The ve loc i t i e s of inward motion of outer zone r e l a t i v e

m a x i m a of t he i n t e n s i t i e s of e lec t rons (E > 1.6 MeV) as

observed a t low a l t i t u d e s with Injun 3 as a function of L.

The ve loc i ty of inward r a d i a l motion of the leading edge

of the outer zone of e lectron (E > 1.6 MeV) i n t e n s i t i e s

a s observed near the equator ia l plane [Frank, 19651 i s

included f o r comparison.

57

Figure 1 4 . A continuation of Figure 11, f o r the period from

Apri l 28 t o May 4, 1963. The catastrophic depletion of

the i n t e n s i t i e s of these electrons was observed during

the same hour i n which the horizontal component of t h e

geomagnetic f i e l d increased by - 200 y a t College, Alaska

(L - 5 . 5 ) .

Figure 15. A comparison of t h e time h i s t o r i e s of t h e i n t e n s i t i e s

of l o w a l t i t u d e outer zone electrons (E > 4.0 keV, > 230 keV,

> 1.6 MeV) a t L = 4.0 - + 0.1 during several geomagnetically

disturbed periods with those of the horizontal component of

the geomagnetic f i e l d a t College, Alaska (L = 5 . 5 ) and the

3-hour values of K f o r the corresponding periods. P

h

THE EFFICIENCIES OF SEVERAL INJUNIII GM. TUBES

AS A FUNCTION OF ELECTRON ENERGY

ELECTRON ENERGY ( KeV)

Figure 1

IO‘

IO’

IO2

IO‘

IO’

IO2

10‘

10’

IO2

10‘

IO’

IO2

THE LOW ALTITUDE TEMPORAL VARIATIONS OF THE INTENSITIES

OF ELECTRONS E>40 KeV TRAPPED IN THE OUTER RADIATION ZONE JANUARY -JULY. 1963

-. - __ - - - - - __ - ---- -

15<B< 17 17<B< 19 19<8<21 2158 < 23 23sB< 25, 25sB< 27 2758s 2 t t-

. F-- _~__-

-1

I I I , , , I , 1 ,

7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28

JAN FEB MAR APR MAY J U M JULY

1963

0‘

I 0’

IO2

IO

I io 2 !O 3 - 08

Y I

IO‘

10’

I O2

Figure 2

E OF ELECTRONS ( E > 4 0 KeV) TRAPPED IN THE OUTER ZONE AT THE ONSET O f

A GEOMAGNETIC DISTURBANCE

I o7

IO6-

I o5

I 04+

G65-6

- 1 I - m-

- -

-THE AVERAGED INCREASE IN THE INTENSiTIEs- - - -

-

- - - - -

-

-

- - - - - -

I I I I 1 I C 0 IO 20 30 4 0

- I

( AVERAGED OVER L = 3.5,4.0,4.5 AND 50) -

3 MAXIMUM Kp DAILY SUM

Figure 3

. G6!5-195

20

18

16

14

12 T

DAYS I O

8

6

4

2

0

- OBSERVED DECAY CONSTANTS FOR

- THE INTENSITIES OF ELECTRONS (E>40KW) TRAPPED IN THE OUTER aONE

DURING PERIODS OF LOW K,

0

a

A

A

FEBRUARY, 1963

MARCH, 1963 -

MAY , 1963

JULY, 1963 -

Figure 4

G 65 - I96

SIMULTANEOUS OBSERVATIONS OF THE INTENSI TIES OF ELECTRONS ( E > 4 0 KeV) TRAPPED IN THE OUTER ZONE AT LOW ALTITUDES AND NEAR THE GEOMAGNETIC

EQUATORIAL PLANE

- 1 I 1 1 . 1 1 i

- I I I I l l 1 __ -

EXPLORER 14 __ - -

I o8

(L= 4.2 f. 0.05, 1.2 L- B 5 5.9 BO

Bo = 0,005 e e

e

e

** e *I--- F" MEDIAN

\

INJUN 3 ( L = 4.0 ? 0.1, 0.18 IB I 0.25 1

I o4 105 I o6 I o7 jL(E> 40 KeV) (CM2*SEC*SR)-'

Figure 5

.

10

IO

IO

IO'

IO?

# IO' 3j s 0' Y W

1 0 5 n v, W [r

IO2

IO'

IOi

IO'

IO'

THE LOW ALTITUDE TEMPORAL VARIATIONS OF THE INTENSITIES

OF ELECTRONS E > 230 KeV TRAPPED IN THE OUTER RADIATION ZONE

JANUARY- JULY, 1963

Q --

1 . , I , , 1 I I I X , . , . d 0 0 1 .LL & m b @ l b W !MW 9 x 1 kaAmRfwv 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28

JAN FEE MAR APR MAY JUNE JULY 1963

Figure 6

lo3

IO2

40 3

302 20 5

B 10 a

Y

0

io3

IO2

IO'

. G 66- 217

10:

IO2

IO'

40

30 a

E 20

IO

0

THE TEMPORAL VARIATIONS OF THE INTENSITIES OF TRAPPED OUTER ZONE ELECTRONS (E>230 KeV)

INJUN 3

L = 3.95 20.05

Y

L=5.0 20.1

4 1 1 f a "s

J

i J i

io3

IO2

IO'

I 5 IO 15 20 25 30 5 IO 15 20 25 30 5 IO 15 20 25 30 M AY JUNE JULY

1963

Figure 7

IO

IO

IO

IO

IO

IO

IO

IO

IO'

IO'

10:

IO'

THE LOW ALTITUDE TEMPORAL VARIATIONS OF THE INTENSITIES OF ELECTRONS E>1.6 MeV IN THE OUTER RADIATION ZONE

JANUARY - JULY, 1963

~ , l l l l ~ , l l ~ ~ , , I I I j j ! / / I , , 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 28 7 14 21 2

JAN. FEE. MAR APR . MAY JUNE JULY

1963

Figure 8

. GRAPH NO. 65-809

- - - io5 - - - 7 - dR dt OF THE INJUN 111 302 GM TUBE -

cu 0

r’ -u

- AT L=4.0 IN THE OUTER ZONE -

FOLLOWING A GEOMAGNETIC -

DISTURBANCE AS A FUNCTION -

OF THE MAXIMUM Kp DAILY SUM T

- io4 1,

M +

DURING THE DISTURBANCE

/ I -

T

’ ‘I

1 LL T I -

15 20 25 30 35 40 45 50 MAXIMUM Kp DAILY SUM

Figure 9

2000

1800

1600

A o 1400 w v)

~

w v) z v) w

I U

2 1000

800

600

400

200

0

G bY

1 I 1 I I I I I I 1 I I I I THE RESPONSES OF THE INJUN 3 302 GM TUBE

TO THE INTENSITIES OF OUTER ZONE ELECTRONS (E > 1.6 MeV 1 FOLLOWING THE

ONSET OF A TYPICAL GEOMAGNETIC DISTURBANCE ,ri' / L = 4 . 0 f 0 . 0 2

L = 4.5 f 0.02 J P A

L=3.5f0.02 r / *.

L.5.5 f0.02 / @// / ./' X Y

//A " / O A Y

//

4 5 6 7 8 9 IO I I 12 13 14 15 16 17 18

JULY 1963

Figure 10

'

LOW-ALTITUDE PROFILES OF THE RESPONSES

AS A FUNCTION OF L FOR SIMILAR PA5Sk.S

MARCH 3-APRIL 12.1963

OF SEVERAL INJUN 111 G.M. TUBES

I-MARCH 31 (1341) 6-APRIL 6 11416) 2-APRIL 2 (1%) 7-APRIL 7 (1428)

3-APRIL 3 (13781 8-APRIL 8 (-1

4-APRIL 4 (1391) 9-APRIL 9 (1453)

5-APRIL 5 114m) IO-APRIL I I (wm I I -APRIL 12 (14901

W v) z 0 v) W

a urn

n N

a n N

3 4 6 = L 7 ti

Figure 11

. THE INWARD MOTION OF SEVERAL SECONDARY PEAKS

IN THE INTENSITIES OF ELECTRONS (E > 1.6 MeV) AS OBSERVED AT LOW ALTITUDES WITH INJUN 3

RE\OLUTION 1957 MAY 19,1963 1417 UT LCCAL TIME 0701- 4 ' 8 0.360

-1 1953

M&Y 13.1963 1221 UT 1

0645- -I '4

MAY 19.1963 0641 UT I 0840- 0.293

1948

1947

* 1944

1 1943

MAY 18.1963 2123 U T I 1531-7

0.214

- c

M&Y 18, 1963 I909 UT 0825 Y 0.311

\ k

* L . b

0

0

\

.5 5.0 5.5 6.0 6.5 7.0 L

5

Figure 12

IOi

IO1

IOC

- 'L

zi W f2 IO1 _I

IO2

103

lo4

G R A W N O 65-?0?

THE RATE OF APPARENT INWARD DIFFUSION

OF ELECTRONS (E>I.GMeV) OBSERVED AT LOW ALTITUDES IN THE OUTER ZONE (INJUN 111, 1963)

m MARCH 11-18 0 MARCH 18-31 A APRIL 7-12 A APRIL 12-70 X APRIL 5 -30 0 MAY 18-19 0 MAY 21 -JUNE 6

I -

j I

t

L

Figure 13

m E N

a rc, N

a E N

LOW-ALTITUDE PROFILES OF THE RESPONSES OF SEVERAL INJUN 111 G.M. TUBES

AS A FUNCTION OF L FOR SIMILAR PASSES

APRIL 28-MAY 4,1963 I-APRIL 28 (1688) 5-MAY 2 ( 1 7 3 ~

2-APRIL 29 (1700) 6-MAY 3 (1m)

3-APRIL 30 (1713) 7-MAY 4 117621 4- MAY I 11726)

- - - - ,. -- -

- - - - - -

- - - -

I00 = - -

-

- - -

- - - - -

- -

3 4 5 6 7 8 L

Figure 14

c

600

w 8

400

z C G , z u a 200 $ 2 8 J g 2

2 0

0

I o4

a 3 lo3 (u

IO2

lo4

lo3

N

0,

Id

IO'

c L 5 y 4

r r 3

7 6

$ 2 I

0

rc)

LOW ALTITUDE ELECTRON INTENSITIES

AT L.4.0 DURING GEOMAGNETICALLY DISTURBED PERIODS

0 .1758<.25 4 .2558<.30 8 ,30585.37

n

E>40KeV

-

0

n " I - I I i I I I I l-

o E > 1.6 MeV - - a- I I I i i I +

-1

8 A

f --I 0

l i i

4 5 6 7 8 9 0 , JUNE-

B 2 9 3 0 3 1 I 2 3 4 5 6 7 8 9 O I I PPRl L -M4RcH--j- I

1963

Figure 15

lo3

m lo2 *3

(u

IO'

- i GSI ; . ;&AT:h G A i T I V , T Y Lorportr lc ourhorj 2 0 R E P O R T S E C U R I T Y C L A S S I F I C A T I O ~

Unclassified University of Iowa Department of FhysIcs and Astronomy , 2 b GFiOUP

I I

- 7cp,-.i?T T -. - $ 1 I &t

The Temporal Variations of Electron I n t e n s i t i e s a t Low Alt i tudes i n t h e Outer Radiation Zone as Observed with S a t e l l i t e Injun 3

’. i 3 E S f ? l ? - i I V L h O T C S :TY,X of report end rnc!usrve dales)

Pr ogr e s s

Craven, John D. 5. A U T h 3 H ( S ) ( L u s : n u x u f i v : - 1

~ ,? _ r 3 F i T r 7 DATE i 7 8 . T O T A L N O . O F P A G E S 7 6 . NO. O F R E F S

April 1966 72 1 4.2 O i l . C G X Y r i A C 7 t 3 G G A h T N O . 1 9 s . O R I G I N A T O R ~ S R E P O R T NUMBER(S)

I ~01-1.r-1509( 96) u. of ~ a ~ a 66-12

’ U P X O J C C T ha.

C I S b O T H E R R E P O R T NO(S) ( A n y othernumbers Lhaf may be essr;nod thrs report)

I I 1

1 0 k V A IL ABILiTY/LlMITATION NOTICES

Qual i f i ed requesters may obtain copies of t h i s repor t from DDC

’ 11. S U P P L EMENTARY NOTES i 12. SPONSORING MILITARY ACTIVITY i I 1 Office of Naval Research

J 1 3 A B S T R A C T

Temporal va r i a t ions of t he i n t e n s i t i e s o f e lectrons ( E > 4.0 keV, > 230 keV, > 1.6 MeV) trapped i n t h e outer r ad ia t ion zone i n t h e region 3.9 < L < 6.0 and mirroring a t a l t i t u d e s of - 1501, km have been studied ;?wing a seven-month period from January 1 t o July 31,’ 1965. by means of t h ree Geiger-Mueller tubes on-board the U. of Iowa/Office of Naval Research research s a t e l l i t e Injun 3. From observations during some twenty geomagnetically disturbed periods, it i s shown t h a t the l a r g e s t i n t e n s i t y va r i a t ions nc~1-n- a t t.he onset of such disturbances and t h a t subsequent behavior is dependent on the magnitudes of the disturbances a s measured by the maximum da i ly sums of the p lane tary magnetic disturbance parameter K . The t i m e h i s t o r i e s of these i n t e n s i t y var ia t ions a r e compared wi?h those of 3-hour averages of t he horizontal component of the geomagnetic f i e l d a t College, Alaska (L = 5.5\1, f o r severa l dis turbed per iods.

(Continued on attached sheet’

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Outer Radiation Zone, Geomagnetical ly Trspped

Radiation

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! ”

HOW- L :

Key words must be / ’

The a s s i g n m e n t of l i n k s , r a l e s , a n d w e i g h t s is opt iona l .

.. ABSTRACT (Cont ' a)

Nearly simultaneous measurements of t h e d i r ec t iona l i n t e n s i t i e s of electrons ( E > 40 keV), which mirror a t low a l t i t u d e s , with Injun 3 , and omnidirectional i n t e n s i t i e s of these electrons near the geomagnetic equator ia l plane, with Explorer 1 4 , indicate similar temporal behavior a t L - 4 . i n the outer zone a t low a l t i t u d e s appear t o occur under a condition of approximate isotropy and equal omnidirectional i n t e n s i t i e s 5 lo8 (c&-sec)-' along a magnetic f i e l d l i n e a t a l l a l t i t u d e s above severa l hundreds of kilometers.

The highest observed i n t e n s i t i e s o f trapped e lec t rons (E > 40 keV)

During four periods of post-disturbance geomagnetic calm, the i n t e n s i t i e s of e lec t rons ( E > 40 keV) were observed by Injun 3 t o decrease exponentially i n t i m e with decay constants T = 12 + 3 days a t L = 3.0, and T = 4 + 2 days i n the region 3.5 < L < 6.0. Simultaneously measured values of the-decay constants for these e l ec t ron i n t e n s i t i e s near t he geomagnetic equator ia l plane a t L - 4 agree, within observational e r r o r . Long-term exponential decays i n t h e i n t e n s i t i e s of a r t i f i c a l l y in j ec t ed e lec t rons (E > 1.6 MeV) w e r e observed by Injun 5 t o be characterized by T = 40 - + 5 and 45 - + 5 days a t L = 3.0 and 3.5, respectively.

Further evidence f o r t he d i f fus ion of e lec t rons (E > 1.6 MeV) i s presented.