I P " -- ___ -A_--

Department of Fhysics and Astronomy

THE UNIVERSITY OF IOWA Iowa City, Iowa

- A u u

0

https://ntrs.nasa.gov/search.jsp?R=19650014702 2020-03-31T23:55:25+00:00Z

4 I

. . .

U. of 1- 65-13

Inward Radial Diffusion of Electrons E > 1.6 MeV i n the

Outer Radiation Zen+

Department of Physics arid Astronomy University of Iowa Iowa City, Iowa

* Research supported in part by the Nationa3 Aeronautics and Space Administration under Grant NsG-233-62 and by the Office of &vi? Eesesrch iiiider Contract Nonr-1509(06).

2

ABSTRACT pW3

Observations of the temporal variations of electron

(E > 1.6 MeV) intensi t ies near the geomagnetic equator i n the

outer radiation zone with Explorer xw (2 October 1962 to

8 August 1963) strongly suggest that replenishment of energetic

electrons i n the outer radiatioc zone during the ceveral weeks

following a period of geomagnetic act ivi ty prmeeirs by an

inward radial motion of energetic electrons Prom L > 5 .

The apparent, inward radial velocity of the “wave” of

electrons (E > 1.6 Me9 is - 0.4 earth radius (rlay)” at

L = 4.7 and - 0.03 earth radius (day)’l at L = 3.4 and varies

as - L8 between these L-shells. These inward radial velocit ies

for the several repleniskiment cycles of outer zone electrons

(E > 1.6 h V ) observed with Ekplorer XIV a t a given L-shell

are equal t o within experimental errors.

provide evidence f o r a continually active mechanism f o r diffusing

These measurements

energetic electrons across Eshells i n the outer radiation zone.

3

I. INTROlXJCaON

The existence of a belt of energetic electrons

(E - 1 MeV) encircling the earth and centered at - 25,000 km

geocentric radia3. distance in the geomagnetic equatorial

plane (i.e., the outer radiation zone) was demonstrated by

in s i t u measurements with some of the earliest earth satellites

and lipace probes [cf. Van Allen, Ludwig, Ray, and I l c l l d n ,

1958; Van Allen md Frank, 1359 a, bl.

energetic electrons i n the interplanetary medium beyond the

earrth's magnetosphere and of energetic electrons precipitated

into the earth's upper atnosphere reveal that the inter-

--

Since measurements of

planetary intensi t ies are insufficient for mintairling the

outer zone intensit ies, a "local" (i.e., within or i n the

immediate vicini ty of the earth' s magnetosphere) acceleration

mechanism driven with the energy of t he solar wind is

generally invoked. i n order t o account fo r the ljnergetic

electrons of t h e outer radiation zone.

zone electron intensi t ies has been stuclied by means of a variety

of Geiger-Mueller tubes and scintilla+,ors on severa l earth

satellites [cf. Forbush e t EL, 1962; McIlwain, 1963; Frank

et al., 1964; Freeman, 1%4].

of these electron intensit ies during end folloWir,g a period of

The morphology of outer

Briefly, the tempord variations

4

r

r

geomagnetic act ivi ty are characterized by (a) 811 immediate

enhancement of - 40 keV electron intensi t ies beyond L 2 3.5

and (b) a severe decrease of - 1 MeV electron intensi t ies a t

the onset of the geomagnetic activity, (c) subsequent decay of

electron E - 40 keV intenaities a f te r the i n i t i a l increase of

intensit ies, (d) m increase of electron E - 1 MeV intensi t ies

within a few days a f t e r the onset of the geomagnetic act ivi ty

a t L - - 5 and an increasing time delay ( - three weeks a t

L - 3.5) for the enhancement of intensi t ies with decreasing

L-value, and (e) a,n orderly decay of electron (E - 1 MeV) in-

tens i t ies after the enhancement of intensi t ies at a given

Eshel l .

l e ] revealed that the temporal variations of the radial

profi le of electron (E > 1.6 MeV) intensi t ies near the geo-

magnetic equator ia l plane were characterized by an inward

radial motion of the inner boundary of the intensity peak

persisting for periods of a t l e a s t several weeks and an

apparent radial. velocity - 0.02 earth radius (day)” follow-

ing a magnetic storm.

indicates tha t in-ward diffusion of energetic electrons across

E s h e l l s from L > 5 i s a soxrcc of energetic outer zone

electrons.

Detailed inspection of Explorer XIV data [Frank e t d.,

This apparent radial mt ion strongly

The follow5ng investigation extends the above

1

5

preliminary analysis of the apparent radial d i f m i o n of

energetic electrons (E > 1.6 MeV) observed by Explorer XIV.

6

The S.U.I. detector array i n Zxplorer XLV (launch,

2 October 1962; apogee altitude, 98,533 km; perigee altitude,

281 km; orbital inclination, 33") included three collimated

Anton type U 3 thin-windowed Geiger-Mueller tubes with differing

par t ic le energy thresholds and an omnidirectional, shielded

Anton type 302 Geiger-Mueller tube. (Rk a detailed descrip-

tion of these detectors, see Frank, Van Allen, and K i l l s

[ 19641 -) Of particular iaterest i n the present investigation

is the response of the familiar 302 G.M. tube (shielding of

265 rcg

t o penetrating energetic electrans (E > 1.6 MeV) i n the

outer radiation zone from L 2 3 to L - - 5 .

the shielded 302 G.M. tube hss been shown to be tha t due to

penetrating electrons (E > 1.6 MeV) over th i s L-sheU range

by demonstrating that the response due t o penetrating 2rotons

E > 23 MeV [McIlwain, 19631 and due t o nonpenetrating electron

bremsstrahlung [Frank, 1962; E'rank e t al., 19641 is negligible

i n comparison t o the penetrating electron response. The omni-

directional geometric factor (EG) of the 30!2 G.M. tube fo r

counting electrons @ > 1.6 M~V)LS 0.1 & 0.05) cm f o r typical

outer radiation zone spectrums; the present study is concerned

magnesium and 400 mg (cm)02 stainless s tee l )

The response of

2

7

with the coqarison of the L-shell profiles of the relative

responses of this detector for sequences of consecutive passes

of the satellite through the outer radiation zone.

response of -the 302 G.M. tube is sanipled for 10.24 seconds

even? 76.8 seconds and the corresponding sanple density is

- 1 sample per 300 km geocentric radial distance along the

portions of the Ekplorer X I V trajectory of interest in the

present investigation.

The

An example of appazent, radial ly inward motion of

energetic electrons (E > 1.6 MsV) as observed by Explorer XIV

has been given by Fraak, Van Allen, and H i l l s c19641 and is

presently reviewed i n Figures 1 and 2. Figure 1 displays the

omnidirectiond intensity profiles of electrons (E > 1.6 MeV)

as a function of L for three similar passes (in magnetic

la t i tude) through the outer radiation zone preceding a period

of geomagnetic act ivi ty beginning on 17 December 1%2. An

orderly decline of intensit ies Over the ent i re L-shell

range displayed here is evident and the absence of the "slot"

or minimum of intensi t ies at L - 3 is due t o a r t i f i c i a l l y

injected electrons framthe Soviet high-altitude nuclear

explosions i n late October and early Noveniber 1962.

these L-shell intensi typrofi les after the period of geomagnetic

activity, Figure 2 clearly shows the systematic movement of the

inner edge of' the intensity prof i le from L 2 3.8 t o L - - 3.3

and a slow decay of peak intensit ies over a period of - 20 aaJrs, and a return of the intensit ies observed a t L > 4.7 t o pre-

storm vctlues by 8 January 1903.

observation of t h i s slow radia3 movement of energetic electrons

that the period of geamag;netic act ivi ty be followed by a period

Continuing

It is essential t o the abwe

.

9

1 .

of several weeks characterized by re lat ive magnetic quiescace

insofar a~ compolmded cycles cannot be easi ly separated i n an

observational sense. For example, the rCp daily sums c Kp for tne period discussed above were > 30 fo r 17-20 December

and - < 15 over the period 23 December 1962 t o 8 January 1963

with the exceptions of c IQ, = 23 and 18 on 26 and 31 December

respectively (see Frank e t a L E19641).

radial velocity of the inner edge of the outer radiation zone

i n the example e v e n above is - 3 x loo2 earth radius (day)-'

at L - - 3.4.

-

The apparent inward

The long operational l i f e t ine of EqLorer XNprovided

several observations of the chain of events discussed above.

Another example of the replenishment of energetic electron

(E > 1.6 b&V) intensi t ies is shown i n Figure 3 for the period

9-24 March 1963 when the sa t e l l i t e passed through the outer

radiation zone along a trajectory of similar B and L every

three days. The intensity profiles of Figure 3 are displayed

as R function of radial distance f r o m the center of easth and

the variations of magnetic latitude for t h i s series of prof i les

are indicated by a sample geomagnetic I n t i t i e given at

30,OOO km for each profile.

temporal. vari;ttions of the p ro f i l e s displayed i n Figure 3 are

The salient features of the

.

10

the characteristic sparsity of electrons during the storm

period on 9 Ma.rch 1963, the subsequent increase of eiectron

(E > 1.6 &V) intensities in the outer radiation zoae until

- 15 March with a peak intensity at a radid distance of

25,000 km during a period of geo-etic activity) and

sdsequent decay of intensities beyond - 25,OOO km with an apparent motion of the peak of intensities inward to - 20,000 km

by 24 March.

suggests that the electron (E > 1.6 MeV) intensities are

rapidly enhanced during the several &ys follaring the initial

decrease in intensities at the onset of geomagnetic actiety

for L > 5 and proceed t o lower bshells by radial diffusion.

Since the rate of radial diffusion is a strong function of L,

increasing rapidly with increasing L, the initial enhancement

for L > 5 shown in Figure 3 can occur by diffusion of electrons

f’rom the vicinity of the magr:etopause but is beyond the

temporal resolution of the Explorer X I V orbit.

the instrunent is sensitive to only electrons (E > 1.6 MeV)

and, if the first adiabatic invariantp is conserved in this

diffusion process, then the electrons which radially drift

into the outer radiation zone to L - 4 with

This set of chronological intensity profiles

Further, since

E - 1.6 MeV

(detector threshold for penetrating electrons ) have

energies 5 150 keV at L =loand hence are well below the

302 G.M. tube penetrating-electron energy threshold. The above

two factors l M t the L-shell range over which we can determine

the rates of inward radial diffusion of these electrons.

The third and final example of replenishment of electrons

(E > 1.6 MeV) i n the outer radiation zone is shown i n Figure 4;

the relat ive intensity contours preceding the period of geo-

magnetic act ivi ty beginning 30 April displayed an orderly decline

over the E s h e l l s 3.2 t o 4.6 with a more rapid decay with in-

creasing L. During the storm period a typical rapid decrease

was detected on the 1 April Explorer XIV pass through the outer

zone on all L-shells presented here with somewhat smaller

decreases on the lower L-shells.

intensi t ies of electrons (E > 1.6 MeV) Were enhanced with

increasing time delay and decreasing anrplitude for decreasing

values of L.

intensi t ies at L = 3.2 may be a maiifestation of the inabi l i ty

of the present experimental appratus t o discern a small

increase of intensities on t h i s L-shell above the intensi t ies

of a r t i f i c i a l l y injected electrons frcin the Soviet high-altitude

explosions (see Figure 2) although the absolute intensi t ies at

L = 3.2 and 3.4 do not differ by more than 30% and the

intensi t ies a t L = 3.4 increased by a factor of

time history of the decay of a r t i f i c i a l ly injected electrons

Following the decrease the

The observation of rio sigr,ificant irrcrease of

5. The

in the "slot" at L - 3 (Figures 1, 2, and 4) indicates that

loss mechanisms i n this region are not more effective than i n

the outer radiation zone [cf. Van Allen, 19641 and indicates

tha t perhaps the presence of the "slot" i s not primarily a

manifestation of a loss mechanism which is more effective along

these Eshel l s but may be attributed t o a weaker source.

temporal intensity profiles of Figures 2 and 4 a l l o w a raugh

determination of the velocities of inward radial diffusion as

a function of L i n the outer radiation zone. These velocit ies

have been estimated by calculating the appsrent inward radial

velocity of the logarithmic half-maxirmrm of t h e inner side of

the "wave" of energetic electrons.

t ion for the two electron (E > 1.6 MeV) replenishment cycles of

December 1%2--Janua,ry 1963 and April-bby 1963 are shown i n

Figure 5.

electrons (E > 1.6 MeV) i s - 0.4 earth radius (day)" and a t

L = 3 . j ~ is - 0.03 earth radius (day)" and the dependence of

t h i s rate of diffusion upon L is - L . velocit ies for the two replenishment cycles are equal a% a

given E s h e l l within the experimentd errors of the present

experiment.

manifestation of the instrument's inabi l i ty t o detect 8 change

i n intensity on this Gshell over the background of art if icially

The

The resul ts of t h i s cdcula-

A t L = 4.7 the apparent rate of inward diffusion of

a The inward radial

The anomalously l o w point a t L = 3.2 ma;y be a

.

injected electrcms. A coarse upper limit of - 0.003 earth radius (aay)-l at L = 2.1 has been obtained

measurements [Van Allen, McIldn, and Ludwig, 1959; McnWain,

19613 of artificislly injected electrons produced by the

Argus tests during 1958.

Wlorer N

It is of interest to note that if

the present result is extrapolated to higher Lshells and

a~suming that this apparent inwaxd radid velocity is not a

strong function of electron energy, diff’usion of electrons f r a n

L - 10 (new the magnetopause) to L 2 5 would take place in a

period of - 1 day, a result which is completely satisfactory

with regard to the temporal resolution of the Explorer XIV

orbit for successive outer radiation zone passes (orbita3.

period of sate l l i te : 36.4 hours).

14

Iv. DISCUSSION

The present study of the temporal variations of

electron (E > 1.6 MeV) intensities in the outer radiation zone

during several replenishment cgcles followixq periods of geo-

magnetic activity strongly inrplizs that inward raCial diff'usion

of electrons from the vicinity of the magnetospheric boundary

is the primary source of the energetic electrcns in the outer

radiation zone L - 3.0. of electrois (E > 1.6 MeV) is - 0.4 earth radius (day),' at

L = 4.7 and * 0.03 earth redius (day)" at L = 3.4 and varies

&6 - L8 between these L-shells. mgnetic activity (roughly, C KJ? & 30) is followed within

approximately 1 or 2 days by the appearmce of large increases in

the intensities of electrons (E > 1.6 I k V ) in the outer radiation

zone beyond L - 5 and the subsequent inward motion of this

wave" of electrons over a period of weeks following the

> !Che inward radial velocity of the "wave"

The onset of period of geo-

n

geomagnetic storm period.

diff'usion of energetic electrons across Lshells is active

durlng periods of relative magnetic quiescence and the r a i d

diffusion velocities (see Figure 5) are equal to within experi-

mental uncertainties for each replenishment cycle of the outer

radiation zone during this period of observations.

The mechanism responsible for this

From

extrapolation of the present result and assuming that the rate

of diffusion is not a strong f'unction of electron energy, it

is estimated tha t approximately 1 or 2 days &re required for

an electron t o diffuse inward from the vicini ty of the

msgnetospheric boundary to L - 5 i n agreemeut with the observa-

t ions of the temporal variations of electron (E > 1.6 MeV)

intensi t ies reported here. Hence it appebs!: that the increases

of electrons@ > 1.6 Me9 intensit ies i n the ou";er radiation

zone reflect , wi th the appropriate t i m e delay, increases of

energetic electron intensit ies i n the vicini ty of the magneto-

pause during periods of geomagnetic act ivi ty as indicated by

ZKp and hence are positively correlated with the solar wind

velocity [Snyder, Neugebauer, and Rao, 1g431.

adiabatic invariant p is conserved as an electron moves by

radial. diffusion from L - 10 t o L - 4, then a 150 keV electron

a t the mapfnetopause w i l l acquire ,., 1.5 MeV upon arrival a t

L - - 4.

for the increases of electron (E > 1.6 MeV) intensi t ies i n the

outer radiation zone an increase of electron (E - 150 keV)

intensi t ies i n the transition region or just within the

magnetopause must be positively correlated with a,n increased

solar wind velocity.

( - lo6 t o 10 cm (sec)"') of electrons E 2 40 keV inside

If the first

>

Hence from tne above interpretation i n order t o account

The existence of large intensi t ies

8 2

the magnetopause is well known [cf. Freeman, 1364; Frank,

19651; and recent measurements [Pan e t al., 1964; Frank and

Van Allen, 1964; Anderson and H a r r i s , 19651 have sham tha t

‘spikes’ of intensit ies of electrons i n t h i s energy range are

frequent i n the transit ion region and are positively correlated

with 3-hour Kp values [cf. Frank and Van Allen, 19641.

[I9601 and Herlofson [1960] have suggested tha t diff is ion is

an ixportant source of enezgetic electrons i n the mter radiation

zone; and recent cElculations by Hess e t al. [19641, Mead and

Nakada [19&], and Nakada e t al. [1$41 assuming that charged

par t ic le trans-L d i m i o n proceeds with conservation of the

ffrst two adiabatic iwariants of motion show t h a t the diffusion

times (i.e., the time required for a charged par t ic le t o mve

from L = 6, f o r example, t o a lower L-shell) would vasy as L

i n agreement with the present coarse experimental result.

Menwain [19651 has recently reported an i m d radial lcovement

of a secondary peak of proton (40 < E < U O MeV) intensi t ies

at L - - 2.2 by 0.15

- 2 x loo4 earth radius (day)” which is only a factor of

- 5 less than tha t given by extrapolation of the present

r e s f i t for electrons (E > 1.6 M ~ v ) to L = 2.2.

of resul ts may indicate that the mechanism responsible for

radial diffusion of chargedparticles i s not strongly dependent

Parker

-0

over a period of two years o r

This comparison

upon particle mass.

present results obtained near solar minimum with obsemtions

during a different portion of the solar cycle by Escplorers V I

and V I I which were also equipped with shielcled 302

F’urther experiments with increased sensit ivity over a larger

energy range, and for longer periods of observation are

necessary i n order t o further investigate diffusion mechanlbrms

8,s sources of energetic electrons i n the outer radiation zone.

It w i l l b e of interest to conrpare the

G.M. tubes.

.

18

I em indebted to Dr. J. A. Van Allen for several stimulat-

ing discussions concerning the present investigation,

research waa supported in part by the National Aeronautics and

Space Administration under grant NsG-233-62 and by the Office

of Naval Research under contract I$om-l503(O6).

This

.

Anderson, K. A., H. K. H a S r i s , and R. J. Paoli, Energetic electron fluxes i n and beyond the earth 's outer magnetosphere, J. Geophys . Res., - 70, 1039-1050, 1965 .

Fan, C. Y., G. Gloeckler, and J. A . Simpson, hrldence for > 30 keV electrons accelerated i n the shock transit ion region beyond the earth's mgnctospheric boundary,

Phys, Rev. Letters, - 13, 149-153, 1964.

Fbrbush, S. E., G. Pizzella, and D. Venkatesan, The morphology m d tpsroord variations of the Van AUen radht ion belt , October 1959 t o December 1960, J. Geuphys. Res.,

- 67, 365103668, 1962.

L. A., Wficiency of a Geiger-Mueller tube for non- penetrating electrons, J. Franklin Inst i tute , 273, 91-16> 1962.

L. A., A survey of electrons E > 40 keV beyond 5 ear th radii with Ekplorer XN, J. Geophys. Res., 2, 1593-1626, 1955 . L. A., arid J. A. VB? ALhen, Measurements of energetic electrons i n the vicinity of the sunward magnetospheric boundary with Explorer 14, J. Geugh:%. Res., 9, 493-4932, 1954

L. A. , 3. A. Van Allen, and H. K. HiUs, A study of charged particles in the earth's outer radiation zone with Explorer 14, J. Geopkiys. Res., - 69, dL[L-zLyL, LYW.

.---- A- -.. - - T I .

.

20

Freeman, J. W., The morphology of the electron distribution i n the outer radiation zone and near the magnetospheric boundary as observed by Explorer XTI, J. Ckophys. Res.,

9, 1691-1723, 1964.

Herlofson, N., Mff'usion of particles i n the earth's radiation belts, Phys. Rev. Letters, - 5, 414-416, 1960.

Hess, W. N., J. W. Dungey, andM. P. Nakada, On fluxes of outer be l t protons, Trans. Am. Geophysical Union, 3, 85, 1964 (abstract).

McIlwain, C. E., Coordinates for mapping the distribution of

magnetically trapped particles, J. Geuphys. Res., 66, 3681-3692, 191.

IJfcIlwain, C. E., The radiat ion belts, natural and artificial,

Science, - 142, 355-361, 1963.

McIlmin, C. E., Long-term changes i n the distribution of the 40- t o 110-MeV trapped prctons, Trans. Am. Geophysical - - Union, 46, 141, 1965 (abstract).

Nead, G. D., and M. P. N&&, The Parker mchanism and protons i n the otlter radiation bel t , Trans. AT. Geophysical - Union, 45, 85, 1g64 (abstract).

Nakada, M. P., J. W. Dungey, and W. N. Hess, Theoretical studies of protons i n the outer radiation bel t , Goddard Space Flight Center Res. R e p . X-640-64-U0, 1964.

Parker, E. N., Geomagnetic fluctuations ami tine Toriii of th? outer zone of the Van Allen radiation belt , J. Geophys.

Res., 9, 3117-3130, 1960.

21

Snyder, C. W., M. Neugebauer, and U. R. €bo., The solar wind

velocity and its correlation with cosmic-ray m i a t i o n s and with solar and geomagnetic activity, J. Geophys.

A, Res - 68, 6361-6370, lg63.

Van Allen, J. A., Lifetimes of geomagnetically trapped electrons of several MeV energy, Nature, 203, 1006-1~, 1964.

Van !=en, J. A., a d L. A. Frank, Radiation around the earth t o a radial distance of 107,400 kilometers, Nature (London), 183, 430-434, 1959a.

Vsn men, 3. A., and L. A. Frank, Radiation measurements t o 658,300 km with Pioneer IV, Nature (bndon), 184, 23.9-224, 1sB.

Van Allen, J. A., G. H. Ludwig, E. C. Ray, and C. E. Mlwain, Observation of high intensity radiation by sa t e l l i t e s 19% aQha and gamma, Jet Prupulsion, - 28, 588-592, 1958

Van Allen, J. A., C. E. Mdlwain, and G. H. Ludwig, Sa te l l i t e observations of electrons a r t i f i c i a l l y injected into the geomgnetic field, J. Geaphys. Res., e, 87'7-891, 1959.

.

22

FIGURE c m o m

Figure 1. Measurements of electron (E > 1.6 MeV) intensi t ies i n the outer radiation zone (Am 5 30") 8s a function of L for several passes of Explorer XIV preceding and

during the onset of geomagnetic ac t iv i ty on 17 December 1962 (after Frank, Van m e n , and H U s , 1%).

Figure 2. A continuation of Mgure 1 W i n g t he geomagnetfca3ly quiescent period a f te r 22 December which fisrlap the

systematic inward motion of the inner side of the peak of electron (E > 1.6 MeV) intensi t ies (mer Frank, V' Allen, and H i l l s , 1964).

Figure 3. A selected set of radial profi les of the omnidirectionaA intensi t ies of electrons (E > 1.6 MeV) for sever& similar Ekplorer XTV passes through the outer radiation zone .

Figure 4. Relative omnidirectional intensity contours of electrons (E L 6 MeV) as a function of time for various E s h e l l s precedi-ng and after the onset of gecmagnetic ac t iv i ty on X April 1963 which display

the i n i t i a l sudden decrease follawed by an orderly replenishment of electron intensities.

Figure 5. Velocity of inward radial motion of the inner edge of the outer radiation zone peak of electron (E > 1.6 MeV) intensit ies as a function of L. straight line h s been drawn through the data points. If these data are f i t t e d wLth a power law kLn

A

1) (see t e x t ) .

,

11-39-?,01

IO'

I

IO!

Jo

IO'

lo I

~

EQUATORIAL INTENSITIES OF ELECTRONS, €2 1.6 MeV

I - DEC. 7, 1962 2- DEC. 13 3- DEC. I7

2.0 ~

3

2

0 L

FIGURE 1

.

IO 8

J O

1 0 4

IOS

EQUATORIAL INTENSITIES OF ELECTRONS, E L 1.6 MeV I - DEC. 7, 1962 4- DEC. 20 5- DEC. 23 6- DEC. 29 7- JAN.8 .1963

laf-37-tjQ 1 I

2 .o 3 .O 4.0 I 0

L

FIGURE 2

I o6

10'

JO

I 0'

10'

IO2

IO5

JO

to4

to3

IO2

RADIAL PROFILES OF THE OMNIDIRECTIONAL INTENSITIES OF ELECTRONS (E-I.6MeV) FOR SEVERAL SIMILAR TRAJECTORIES

DURING GEOMAGNETIC STORM PERIOD

-- \ I I I

1 I

:CM2-SEc)-'I I -21"

I

- 10 20 30 40

' I ' l l / -23*

POST- STORM

-21"

) 20 30 40

- - 2 2 O I

[MARCH] 1 I I I 1 I I

I 20 30 x 103 KM RADIAL DISTANCE FROM THE CENTER OF THE EARTH

FiGiiiii 3

> I- CT: z LL I- 2

LL

I-

LL CK

-

-

2 a -

TEMPORAL VARIATIONS OF THE INTENSITIES OF ELECTRONS (E > 1.6 MeV) FOR SELECTED L-SHELLS IN THE OUTER RADIATION ZONE

EXPLORER X I E -

e e

-

- -// I //- f L 4 . 2

\ I 7 /

FIGURE 4

I .o

IO-

10-2

10-3

APPARENT RATE OF INWARD DIFFUSION OF ELECTRONS ( E > 1.6 MeV) IN THE OUTER RADIATION ZONE

/ /

/ /

/

EXPLORER XE

0

0

DEC, I962 - JAN., I963

APRIL- MAY, 1963

f-

2 .o

/ ' /

/

T

3.0 L

FIGURE 5

4x) 5.0