June 1966 - NTRS - NASA

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June 1966. *Research supported in part by the National Aeronautics and Space. Administration under Grant NsG-233-62 and by the Office of Naval. Research ...

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U . of Iowa

66-13

EXPLORER 1 2 OBSERVATIONS OF CHARGED PARTICLES I N THE INNER RADIATION ZONE*

K . L . Ackersonw and L . A. Frank

Eepartment of Physics and Astronomy U n i v e r s i t y of Iowa Iowa City, Iowa

June

1966

*Research supported i n p a r t by t h e National Aeronautics and Space Administration under Grant NsG-233-62 and by t h e O f f i c e of Naval Research under Contract Nonr-1509( 0 6 ) . HGraduate Research Fellow o f the National Aeronautics and Space Administration.

D i s t r i b u t i o n of t h i s document i s unlimited.

f 2

Measurements of e n e r g e t i c charged p a r t i c l e s i n t h e i n n e r r a d i a t i o n zone with two s h i e l d e d , omnidirectional Geiger-Mueller t u b e s flown on Explorer 1 2 have been used t o c o n s t r u c t B-L contours of the omnidirectional i n t e n s i t i e s of protons E > 2 1 Mev and E > 70 Mev f o r t h e p e r i o d P P

16 August t o 19 September, 1961, p r i o r t o t h e S t a r f i s h high-

9

a l t i t u d e nuclear b u r s t on

July 1962.

The v a l u e s of proton

> 2 1 Mev) omnidirectional i n t e n s i t i e s a r e i n s u b s t a n t i a l (EP agreement with t h e p o s t - S t a r f i s h v a l u e s from T e l s t a r 2 and with o t h e r observations.

Upper l i m i t s f o r t h e omnidirectional

i n t e n s i t i e s of e l e c t r o n s E

e

> 1.6 Mev a t t h e geomagnetic

-1 4 2 equator b e f o r e t h e S t a r f i s h t e s t are Jo < 10 (cm - s e e ) a t L = 1.2,
2 1 Mev and > P ranges 1 . 2

34 Mev i n t e n s i t i e s by a f a c t o r of P h i g h e r L-values L September

,> 2.5

-

10 a t

during a. geomagnetic s t o r m i n

1963 have been r e p o r t e d by McIlwain [1965]

[ s e e a l s o Gabbe and Brown,

19651.

Observations during t h e

next few y e a r s of i n c r e a s i n g geomagnetic a c t i v i t y w i l l be of fundamental importance toward i d e n t i f y i n g and understanding t h e predominant loss and a c c e l e r a t i o n mechanisms f o r i n n e r zone protons. A secondary maximum of proton

u n i d i r e c t i o n a l i n t e n s i t i e s , j,,

at L

(40 < E < 110 Mev)

-

P 2.2 on t h e magnetic

equator was observed with Explorer 15 i n l a t e 1962 [McIlwain,

19631. Explorer 1 2 measurements of t h e omni-

d i r e c t i o n a l i n t e n s i t i e s of protons E

P

> 2 1 Mev and > 70 Mev

a t t h e geomagnetic equator as summarized i n F i g u r e s

7

and

8, r e s p e c t i v e l y , show only a change of slope i n t h e equatorial i n t e n s i t y versus L p r o f i l e s i n t h e region

2 - 1