Final Report

for

Energetic Particle, Flux Expeeiment (AIMP-D & E):

('28 J @ I ~ P ~ - 1965 to 31 October 19'9)

Cazitract NO.: NAS 5-9077'

Space Sciences Labaxatory University af Cgdffornia

Barkeley,, C'aliforhia 94720

Potncfpcl ImeatQoto~: lC: A. Andax so.

fur

https://ntrs.nasa.gov/search.jsp?R=19710004903 2020-01-28T23:26:19+00:00Z

Space Sciences Labora tory Series I I , I s sue '75

Fina l Report

f o r

Energet ic Pa r t i c l e Flux Experiment (AIMP -D & E) '

( 2 8 Janua ry 1965 to 31 October 1969)

Contract No. : NAS 5-9077

P r e p a r e d by

Space Sciences Laboratory University of California

Berkeley, California 94720

Principal Investigator: K. A. Anderson

for

Goddard Space Flight Center Greenbelt , Maryland-

TABLAE OF CONTENTS

Tit le page

Abstract

Lis t of Il lustrations

I. Technical Description of Experiments

11. Description of the Data Format on Magnetic Tapes Supplied to the National Space Science Data Center

111. AIMP- 1 , 2 Major Computer Process ing P rograms

IV. Lis t of Publications Reporting Results f r o m the Explorer 33 and 35 Satellites

V. Pape r s Presented a t Scientific Meetings Reporting Results f r o m the Explorer 3 3 and 35 Satellites

ii, ABSTRACT

This repor t summar i ze s the scientific usage of the data frorn

the Universi ty of California exper iments aboard Explorer 33 and 35

( A M P - 1 and 2). Basically, t h r ee major f ie lds of study have been

pursued in the analysis of the data. These a r e energe t ic so l a r

par t i c les i n the interplanetary medium, t e r r e s t r i a l par t ic le f luxes in

the magnetotail and magnetosheath-bow shock regions , and lunar

effects on energet ic par t ic les . Much of the work on so l a r par t ic le

s tudies i s based on comparisons with simultaneous observat ions on

o ther spacecraf t (IMP-3, OGO-1 and - 3 , OGO-5, IMP-4 and -5) a s

well a s with ground-based optical and radio observat ions ,

Studies of t e r r e s t r ia1 f luxes have concentrated on the "island"

f luxes , the distant (-60 R ) magnetotail , and the magnetosheath and e

bow shock spikes which a r e observed even -60 Re ups t r eam f r o m

the e a r t h i n the in te rp lane ta ry medium.

Lunar par t ic le shadow studies , utilizing both so l a r and t e r r e s t r i a l

par t i c les , have proven to be v e r y fruitful i n delineating the structure

and dynamics of the magnetosphere . Work i s continuing on energet ic

par t ic le in teract ions with the moon.

Much of the work on th i s contract has been done by students.

P a r t of the PhD thes i s of Dr. Rober t P. Lin was based on Explorer -33

data. Dr. S. W. Kahler a l so part icipated ir joint OGO- 1 and -3 and

Explorer -33 - and 35 studies of so l a r events a s par t of his graduate

work, R , E , McGuire, cur ren t ly a graduate student, is involved with

continuing work on lunar particle shadows. He has recent ly completed

a theore"tica1 study of particle sihadows based on the observations of

of Explorer-35,

*1L,

A substantial a L x L o ~ t of 'work h a s been done s;r;c? i s continning

t o be done in col labora t ion with other exper imenters on these s ame

spacecraf t a s well a s with exper imenters on other spacecraf t . Much

ana lys i s r ema ins to be done on the Explorer -35 data.

All of the Explorer-33 and the f i r s t year of Explorer-35 data

has been edited and submitted to the National Space Science Data

Center.

The r e s t of the repor t consis ts of the following:

I. Technical Description of the Universi ty of California exper iments

on Explorer 33 and 35.

11. A Description of the Data Tape Fo rma t .

111. A s u m m a r y of the computer p rog rams developed to p roces s the

data fo r the Universi ty of California exper iments .

IV. A bibliography of the a r t i c l e s published o r submitted fo r publi-

cation that a r e based on data f r o m these exper iments and a List

of papers given a t scientific meet ings which a r e based on data

f r o m Explorer 33 and 35.

iv,

LIST QP ILLUSTRATIONS

The Explorer -33 package shown he re i s located on the top of the

0 spacecraf t . Both the open and sca t t e r counters look out a t 90

to the spin axis. The Explorer-35 package i s identical except

both GM counters look along the spin axis.

The measu red efficiency of the Geiger-Mueller tubes with 1.2

2 mg/crn2 and 0.7 rng l cm m i c a windows i s shown h e r e a s a function

of energy.

This f igure i l lus t ra tes the uniformity of the scat ter ing efficiency of

the gold foil over a wide range of e lect ron energies.

2 The efficiency of the 0.7 m g / c m mica window open counter aboard

Explorer -33 for counting x - r a y s has been calculated and i s shown

h e r e a s a function of x - r a y wavelength.

In this calibration of the Geiger-Mueller tube the incident f lux of

x - r a y s is proportional to the beam current . The count r a t e of the

GM tube a s a function of f lux i s well descr ibed up to -5000 counts

pe r second by a simple dead t ime correction.

Schematic of the Neher-type integrating ion chamber c a r r i e d ahpard

Explorer -33 and 35.

Calibrations of the Explorer -33 and 35 ion chambers fo r radiation

dosage.

The ion chamber efficiency for e lec t rons and protons a s a functio-I

of energy was calculated f r o m range-energy curves and shown

he re , The detection efficiency f o r the Explorer-35 chamber ( left

hand scale) is different frorn these curves by the factor obtainable

from Figure 7 ,

Block d iagram of experiment,

10, "S-T" accumulator,

I I. Ion chamber timing,

12, Output timing,

13. Te lemet ry format .

14. Bit locations,

15. F o r m a t of the data tapes f r o m the University of California

experiment on AIMP-1 and 2.

I ,

I, T ECHNICAL DESCRIPTION OF EXPERIMENTS

'f he Univer sity of California experiments aboard Explorer - 3 3

and -35 each co~i ta in two Geiger-Miieller tubes, one of which luoks

direct ly a t part icle fluxes while the other observes the particle flux

backscat tered off an 8 mil gold foil. Protons lose energy in the

gold foil without backscattering while e lectrons backscat ter with high

efficiency and l i t t le energy 10s s. With this a r rangement , proton

and electron fluxes can be identified and separated.

In Explorer-33 the open counter, GM2, and the s ca t t e r detector,

GM1, a r e both pointing a t 90' to the spin axis while in Explorer-35

both detectors point along the spin axis. GM1 i s a Lionel 205 HT

Geiger-Mueller tube with a s tandard thickness mica window while

GM2 i s a thin-window vers ion of the s ame tube with an energy

threshold of about one-half a s high a s fo r GM1. Thus fo r e lectrons

it i s possible t o derive some energy spec t rum information about the

fluxes. A 4-inch ionization chamber completes the detector comple-

ment which i s shown in F igure 1. Table 1 summar i zes the charac-

t e r i s t i c s of the detectors.

The Lionel 205 HT Geiger Mueller detector has a cylindrical

cathode of 2" inside diameter , and i t i s sensit ive t o radiation over

the en t i re $I' dia,meter window. This tube has a 1. 2- 1 .4 m g / c m 2

mica window, and a typical e lectron detection efficiency ve r sus

e lectron energy curve i s shown in F igure 2. The threshold, a rb i t ra r i ly

d e f i n e d a s the I / r e f f i r j ~ n c y point, i s about 40 XceV for these t t i i ~ ~ s .

GMZ i s a special thin-window (0. 7 mg/cm2 mica) modified Lionel

205 HT, The window diameter has been necked do-wn to 0 . 17" i t1

SPIN AXIS

OPEN COUNTER

INTERCONNECTION TO SPACECRAFT

UN lVERSlTY OF CALIFOR NIA EXPERIMENT PACKAGE FOR EXPLORER 33

F i g u r e 1

Table 1

EXPLORER 3 3 AND 35 DETECTOR CHARACTERISTICS

Direct ional Omnidirect ional Geome t ry F a c t o r Angle Sensit ivi ty Sensit ivi ty Omni- L,ook to

Detector Direct ional d i rect ional Angle Spin Designation 'Type of Detector Window Elec t rons P ro tons E lec t rons P ro tons cmd-s t e r c m 2 FIIVHLW Axis

GM1 Lionel 205 I-IT 1 .4 > 4 5 keV None > 4 MeV > 4 0 2 . 4 ~ 1 0 - " ~ 0 . 7 5 - b o o 90" on 33 CM tube i n m g / c m 2 MeV on 3 3 s c a t t e r configu- m i c a (3 . 6 x (zoo on ration. on 35) 351

Lionel 205 HT 0.7 > 2 2 keV > 0.3 > 4 MeV > 4 0 0.29 N O . 75 - 75" 90° on 33 thin window GM m g / c m 2 MeV MeV

m i c a (oO o n 35) tube

Ion 4" d i ame te r 21 0 - - - Chamber spher ica l m g / c m 2

Neher-type a luminum integrating ion skin chamber

- - - > 0.7 > 12 MeV - - - -80 MeV Maximum

sensi t iv i ty -17 MeV

0.7 MG/CM MICA

1.2 MG/CRII MICA

EFFICIENCY OF M TUBE AS A FUNCTION OF ELECTRON

ELECTRON ENERGY IN KILOELECTRON VOLTS

F i g u r e 2

5

o r d e r "c osupport the mica window against p ressure . Its response ttl

e lec t rons is a l so shown in F igure 2, A s can be seen, i t s threshold

i s about 22 lceV for e lect rons ,

The proton response of these tubes i s calculated f r o m range

energy cu rves given by ~ r o w e r l a f te r the tube window thicknesses

a r e cal ibrated with an a lpha-par t ic le source.

The 8 mi l gold sca t te r foil used in GM1 provides effective

discr iminat ion against protons. All par t i c les seen by the counter

m u s t backscat ter off the foil. P ro tons lose energy before they a r e

s ca t t e r ed through la rge angles, a s can be i l lus t ra ted by calculating

the r m s scat ter ing of a 10 MeV proton in a length equal to its

range. F r o m Fe rmi : "

3 where N = number of a toms pe r c m , D = length of t r a v e l (placed

equal t o the range) , z = charge of par t ic le = 1 fo r proton, Z = charge

of s ca t t e r = 79 fo r gold, e = e lec t ron charge, V = velocity of par t ic le ,

p = momentum of part icle, and a. = Bohr radius. We obtain

IIT 0.2 radians m 10'

T e s t s on the efficacy of the s ca t t e r foil f o r proton rejection were

conducted using a cyclotron beam of 4 MeV protons,' An upper limit

of 0 , I Ojo was oh%a,ined fo r the proton detection efficiency, Fr~rthermore

the observat ion of so la r proton events in space has confirmed that

the count r a t e of the sca t te r counter due t o backscat tered protons

i s negligible,

*

Electrons backscatter off the gold foil with high efficiency, A

well referenced t reatment of electron sca tke ing is contained in

~ i e g b a h n , " and only the pertinent resu l t s will be mentioned here, The

8 mi l gold foil i s thick enough to insure saturation backscattering of

electrons of a few MeV o r lower energies. Fifty per cent of a normally

incident beam of electrons and 7070 of a diffuse beam will be back-

scat tered f rom the gold foil. The angular distribution of the back-

2 scat tered electrons will be approximately cos 8 in angular dependence.

Neither the backs catter efficiency nor the angular distribution of the

backscattered electrons i s dependent on the energy of the incident

electron. However, energy loss occurs in the scattering foil. Mea-

surements indicate that for a heavy element such a s gold the probable

energy loss i s about 5-lo%, with about two-thirds of the particles

losing l e s s than 20y0 of their energy, The effect of th is energy los s

i s two-fold:

1. The energy threshold of the scat ter counters a r e about 5 keV

higher than the bare GM tube, and

2. the counting efficiency versus electron energy curve i s not

quite a s sharply falling.

Thus the scat ter counter's (GM1) threshold is about 45 keV for

electrons, F r o m the above considerations the scattering efficiency

would be expected to s tay fa i r ly constant over a wide range of electron

energy above the threshold for the scat ter counter, Figure 3 shows

the measured efficiency versus energy fo r the IMP-3 sca t te r counter

configuration,' which i s similar to the G M l detectors flown here.

MEAN ENERGY OF ELECTRON BEAM (keV)

IMP I , II ,m GM I SCATTER COUMEER CONFIGURATION

F i g u r e 3

8,

On Explorer-33, CPd2 is pcintrd at r ighhangles tc thc spin

0 ax i s and the spin axis i s pointed only 4 off the ecliptic plane, The

init ial orientation of the spin ax is just bare ly allows GM2 to s e e the

sun; however, a s the sp in axis-sun angle changes due to the orbi ta l

motion of the ear th , GM2 s e e s m o r e and m o r e of the sun. Because

of its v e r y thin window GM2 i s quite sensi t ive t o so la r x - r a y s i n

0 the 1-14A region, and i t s background count r a t e i s due p r imar i l y t o

such x- rays .

The x - r ay response of these counters can be calculated i f the

composition of the mica window and the f i l l ga s i s known. If a n x - r a y

beam of intensity I ( A ) is incident on a m a t e r i a l of thickness, R , then 0

t he intensity of the penetrating beam i s

where p = density of the mater ia l , and 0 ( A ) = cross-sect ion.

1 o(A) = - pioi ( A )

1

where p. = density of e lement i in the ma te r i a l and o.(A) = c ros s - sec t i on 1 1

fo r e lement i.

F o r an x - r a y t o be counted by the Geiger-Mueller tube, it mus t

penetra te the window and s top i n the gas , Therefore , the counting

efficiency i s given by

9,

Us ing the cross-sect ions kindly supplied by L, Acton (private

communication), the calculation has been car r ied for GM2 of

Explorer -33. The resulting efficiency curve i s shown in Figure 4.

The detectors on Explorer-35 point along the spin axis which i s

oriented perpendicular to the ecliptic plane so that no solar x- rays a r e

counted by them. The GM tubes a r e shielded with 1.5 of brass .

This shielding is in addition to the spacecraft packaging and outer skin

2 so that the total shielding is about 2.0 g l c m . Range-energy curves

were used to determine the threshold energies for penetrating particles.'

The Geiger -Mueller tubes have dead t imes following a pulse.

These dead t imes change at ve ry high count r a t e s since the voltage

a c r o s s the tube never recovers completely after a pulse before a new

pulse s ta r t s , The variation of the count r a t e with flux i s shown in

F igure 5 for GM1 of the Explorer-33. The assurnption of a constant

dead t ime fi ts the curve well over the tube 's useful dynamic range, and

individually fitted dead t imes a r e used to co r rec t the count r a t e s of

the detectors. These a r e entered a s constants in the data processing

format (Section 11) and a r e typically 1 o - ~ seconds.

The GM detectors have a FWHM opening angle of ~ 7 0 ~ . On

Explorer-33 the detector points 90° to the spin axis so the count ra te

i s an average over a large cone of angles. In most applications, the

GM data is t rea ted a s an omnidirectional average.

Ionization Chamber

A schematic of the i o n chamber carr ied aboard Explorer-33 is

shown i n F igure 6, This is an integrating Weber-type ionization

chamber. The operation of the charnber i s straightforward, The

,tungsten whisker flicks over and charges the anode to 700 volts,

LLJ - 0 - Lb LL. LrJ

4 6 8 10 12 14 WAVE LENGTH (%)

EXPLORER 33 DETECTOR GM2 MICA WINDOW NEON GAS FILL ING

F i g u r e 4

GMl RATE

EXPLORER 33 X -RAY CALIBRATION DETECTOR GMI

5 10 15

CURRENT (MA)

Figu re 5

" 7 0 0 VOLTS 8 4-

TUNGSTEN WHISKER

SCHEMAT C, 4" ION CHAMBER

F i g u r e 6

13,

Then " t h e anode collects electrons from ionization in the chamber,

making the anode voltage drop, When the drop in anode voltage

c rea te s a powerful enough eieetrostatie force on the whisker, the

whisker flicks over and recharges the anode. The pulse created by

the recharging is recorded and represents a specific amount of ioni-

zation i n the chamber, The calibration curves of the Explorer-33

and 35 chambers a r e shown in Figure 7.

The response of the chamber to protons and electrons of

different energies can be calculated. F o r ve ry high energy (minimum

ionizing) particles which penetrate the spacecraft the calculation i s

fa i r ly simple. However, for low energy part ic les both the thickness

of mater ia l surrounding the chamber, and the varying ionization loss

of the particle with energy must be taken into account. The amount

of energy lost in the chamber can be calculated f r o m range-energy

curves, and the mater ia l t o be t r ave r sed before entering the chamber

m a y be estimated f r o m considerations of the ion chamber location on

the spacecraft. F igure 8 gives the resu l t s of such calculations.

F o r the Explorer-33 and 35 ion chambers the t ime span between

pulses i s measured to milliseconds and read out every 40.96 seconds,

Thus the t ime resolution of the Explorer-33 and 35 ion chambers i s

an inverse function of the radiation level. At galactic cosmic r a y

background levels the t ime resolution i s about t en minutes.

The data from the detector i s fed to one 1%-bit and three 16-bit

accumuPators lacl the d ig i ta l data pvoceasor of thc spacecraft e ~ c o d e r

after appropriate amplifica"&on, shaping and timing, A l l aeeurr ,ulato~s

RADIATION LEVEL ROENTGENS PER HOUR

Figu re 7

9

e EXPLORER 33 0 - ION CHAMBER RESPONSE

>-. x __)--

0 _- ELECTRONS v

Z L 6 PROWNS

k"" J c g k & la,"<

L z s o w F 2 0 0

P A 3 u LLJ O9

3 a w

8 0.1 I 10 100 1000 10,000

PARTICLE ENERGY (MEV)

F i g u r e 8

are reset after readout, The experiment block diagrawz is givea in

F igu re 9,

The two GM tubes feed accumula tors di rect ly a f te r pulse

shaping and amplification. These accumulators a r e the "S-TI' type

which will count signal pulses (S) up to the maximum of the accumu-

la to r (215-1) and will then count clock pulses (T) fo r the r e s t of the

accumulation period.

The purpose of the "T" mode is t o allow fo r a n accura te in te r -

pretation of a n overflow condition ( w h e r e m o r e pulses occur than can

be counted during the accumulation t ime of a conventional, "S" mode

counter). F o r each GM tube readout, a single 16-bit accumulator

(e i ther #5a and #6a) i s used. If the 16th bit i s "0" then the readout

i s the number of pulses acquired i n the accumulation period. If the

16th bit i s "1" then the f i r s t 15 bi ts of the accumulator give the

number of clock pulses acquired a f te r the overflow.

F r o m F igu re 10a, it can be s een that the l a s t bit of the "S-T"

accumulator i s used f o r control t o switch over and count the clock

ins tead of signal inputs. The clock frequency selected (800 Hz) i s

such that the accumulator would not overflow if the clock were counted

fo r the en t i re accumulation period. Therefore , a s s een i n F igure l ob

the counting r a t e of the detector i n the T mode i s calculated by using

the equation

Rate - - 215 3 9 - 6 8 -- T

where T = T 800

and N i s the count telemeterred in the 'IT" mode,

U CAL EXPERIMENT-!+SPACECRAFT I

I I

St: 5 SYNC.

F i g u r e 9

SIGNAL

I 800 HZ CLOCK

1.28 39.68 SEC. S EC

F i g u r e 1 0

For the i ~ n chamber, ece 12-bit 2nd cne !&="at aecum-ctlatsr 1s

used (#5b and #6b) ; one de te rmines the total number of counts during

the accumulation period while the other provides a measurement of

the t ime period between ion chamber pulses. This method i s used

because of the typical low count r a t e s and wide dynamic range of

- 3 2 th is detector (10 Hz to 10 Hz).

The #6b accumulator i s used to m e a s u r e the tota l ion chamber

counts per accumulation interval . The signal f r o m the ion chamber

i s amplified and t r i g g e r s a one-shot mul t ivibrator which i s used t o

d r ive the #6b accumulator c i rcui ts .

Accumulator #5b and the ion chamber logic c i rcu i t s a r e used fo r

the period measurements , A dual t ime-base technique i s used - - the

1600 Hz clock and the 40.96 second repeti t ive t i m e between the #5b

accumulator readouts, (Refer to F igu re s 9 and 11.) The output of

th i s accumulator can r ep re sen t any of the following:

1. The e lapsed t ime (T1 o r T ) between the ion chamber 2

pulse and the s t a r t of the #5b accumulator f r eeze t ime.

2. The elapsed t ime (T3) between the f i r s t pair of ion

chamber pulses occur r ing during the accumulation t ime

of accumulator #5b.

3. The presence of a n ion chamber pulse that occur red

during the f r eeze t ime of the #5b accumulator , "hidden

pulse. "

Flip-flops #I a,nd #2 a r e r e s e t a t the beginning of the #5 accumu-

lator freeze time a,nd flip-flop # 3 i s r e s e t a,t the end of "ce # 6 accumu-

bator freeze time, The ion chamber output, after shaping by the

one-shot mul t ivibrator , t r i g g e r s flip-flop # 1 which gates the 1600 Hz

FREEZE READ

a5 SYNC.

IC PULSES

Figure 11

clock into the #5b aeeuri?ulator, If there a r e nu other ion chaenher

outputs before the a c c m u l a t i o n period ends, then the clock count i s

stopped by resett ing flip-flop #2 with the #5 sync (accumulator freeze),

The stored count in the accumulator then represents T (or T2)" 1

This same process i s repeated each time there i s only one ion chamber

pulse per accumulation period. Thus, by knowing T1, T2 and the

number of no pulse readouts that have occurred between them, the

period T of an ion chamber pulse pair can then be calculated.

If a second IC pulse occurs during the accumulation t ime of #5b,

then this pulse will toggle flip-flop #1 back to i t s original state, and

thus block fur ther clock pulses f rom reaching the #5b accumulator.

This action of flip-flop #1 will a lso set flip-flop #2 and prevent any

fur ther toggle pulses f r o m reaching flip-flop # l . Thus, the count

contained in the #5b accumulator will then represent the t ime T g -- that i s , the period between the f i r s t pair of pulses occurring in the

accumulation interval.

Since the re i s a probability of an ion chamber pulse occurring

during the f reeze and readout t ime for the #5b accumulator ("hidden

pulse") and since this could be significant for period measurement a t

the low count ra tes , a means i s provided to identify the occurrence of

these pulses, Flip-flop # 3 and the two associated gates a r e used for

this purpose (Figure 9). If an IC pulse occurs during the #5 freeze

t ime it i s sensed in a logic gate and used to set flip-flop # 3 , Flip-

flop # 3 then se rves a s a memory and this condition is then readout

during the $6 f r e e z e time via a gate and passed into the aceumda"cor

#5b "c reg is te r as a single count, Thus, when the IC period: 'IT, "

i s grea ter than 39,68 seconds these "hidden pulses" a r e identifiable

2 2,

by a single c ~ i k n t in the #5b acc~mula toz - - with IC periods l e ss $ha:?

39.68 seconds this single count cctuld be covered up 'by 1600 Hz c lock

pulses.

The genera l equation f o r computing the ion chamber period, T ,

when a single (and no pulse) occur during the #5b accumulation t i m e

can be given a s ,

whe re T = the IC period i n seconds

N2 = the presen t #5b readout (accumulated counts)

N1 = the l a s t #5b readout > 1 preceeding the N2 readout

NZ = the number of #5b readouts which have been 0 ' s o r

1 's between the N1 and N2 readouts

N = the number of #5b readouts which have been 1 ' s

between the N1 and N2 readouts.

When 2 o r m o r e pulses occur during the #5b accumulation t ime

the period, T , f o r the pulse pa i r i s

where N = the accumula.tion count i n #5b. P

The Unjvers i ty of Calsorn ia experi-ment uses three 16-bit a,ccumu-

lators and one IZ-bi t a ecmlu l a to r in the Digital Data P r o c e s s o r (DDP)

s e e t i ~ n of the spacecra f t Encoder, Each accumulator i s r e a d out and

2 3 ,

r e s e t " t ~ i c e every spacecraft seguexee, An a d d i t l o ~ a l 4 b i t s are ased

f o r a. rediundaney cheek on the H6a accumuPator,

Figure 12 shows the re la t ive t iming for each of the 4 outputs

f r o m the experiment. The f r eeze and readout of accumula tors #5a

and #5b occurs a t the s a m e t ime , (This is a l so t r u e for #6a and #6b,)

The #5 accumulator readouts l ead the #6 accumulators readouts by

2.56 seconds.

The t e l eme t ry fo rma t positions fo r one sequence a r e indicated i n

F igu re 13. During each channel, two 4-bit (hexadecimal) bu r s t s a r e

t ransmit ted. The 4 mos t significant bits of accumulator #6a a r e r e -

t ransmi t ted a s indicated i n F igure 14 -- bit 1 i s the l e a s t significant

bit,

All detectors operated normal ly f r o m launch on June 30, 1967

until August 1, 1967. On August 1, GM2 of Explorer-33 began to

behave e r ra t ica l ly , At t h i s t i m e it was counting a n average 3000

counts per second f r o m so l a r x-rays . By August 4, the count r a t e of

GM2 had r i s e n t o 10,000 counts p e r second, which was higher than

the saturat ion r a t e achieved in labora tory t e s t s . On August 9, GM2

stopped counting and a few days l a t e r GM1 a l so stopped. Studies in

the labora tory on s imi l a r tubes indicated that GM2 had apparent ly gone

into a neon l a m p type discharge, and drawn enough cu r r en t to lower

the power supply voltage below the s tar t ing potential of GM1, This

malfunction may have been due to two causes:

1, loss of some gas from the counter, due d o a pinhole leak

i n the ve ry thin window of the counter, o r a leak e l s e -

where in the counter walls; o r

I C CLOCK (5b)

IC COUNT (6 b)

I I

# FREEZE 8 READOUT

F i g u r e 12

CHANNEL

FRAME O

LAST 4 BITS O F +6 a RE-TRANSMITTED

FRAME 15

FRAME I@ --- --

I SEQUENCE = 16 FRAMES = 81.32 SECONDS (NOMINAL)

Figu re 13

ACCUMULATOR

LOCAT18NS

FROM ACCUMULATOR 6 a

F i g u r e 14

2, absorption of the queaching gas on the walrs of the couster

f r o m t h e catalytic action of the large x-ray flux,

On September 2 , 1966 the current drawn by GM2 became sufficiently

l a rge to lower the supply voltage and stop GM1 also. The ion chamber

with a lower voltage threshold of 350V continued to operate until

October 20, 1967. No usable data was obtained af ter that date,

All detectors operated normally f r o m launch on July 19, 1967

until November 17, 1967, At that t ime detector GM2 began exhibiting

occasional spikes i n its counting ra te which m a y be due to either

partial breakdown of the quenching gas o r a malfunction i n the accu-

mulator. In this r ega rd it is noted that the occurrence of the spikes

was count ra te dependent, occurring more often at higher counting

rates . Also the interval between spikes appeared to be somewhat

regular, The data remained quite completely usable since these

spikes were fair ly constant in counting r a t e s and therefore never con-

fused r ea l events. On November 19, 1968 af ter a particularly intense

so lar event the ionization chamber failed. We believe the tungsten

filament welded itself onto the anode of the chamber. On May 9, 1969,

the GM2 (open detector) ceased to count following an intense solar

event in April, P r i o r to the termination of counting, GM2 exhibited

4 a continuou.~ discha.rge mode, counting b 10 counts/sec, probably due

to the los s of the quench gas, GM1 continued counting and a s of

M a y 14, 1970 was st i l l operating normal.ly,

1. T rower , W.P. ,

Ma t t e r , Univers i ty of California, Lawrence Radiation

Labora to ry , Berkeley, Publicat ion UCRL- 2426, 1966

2. Fermi, E., Notes compiled by J. O r e a r , A.H. Rosenfeld,

and R.A. Schluter , Univers i ty of Chicago

P r e s s , Chicago, I l l inois, p. 36, 1950

3. Anderson, K. A., H. K. H a r r i s and R. J. Paol i , J. Geophys.

Res . , - 70, 1039, 1965

4. Siegbahn, K., Alpha-, Beta- and Gamma-Ray Spectroscopy,

V1, N. Holland Publishing Co., Ams te rdam, Netherlands, - 1965

a, BESGRICPTION O F THE DATA FORMAT ON MAGNETIC TAPES S'LIPPLIED TO THE NATIONAL SPACE SCIENCE DATA CENTER

The magnetic tapes submitted to the National Space Science Data

Center contain all the data f r om the University of California experi-

ments on the AIMP-1 and -2 spacecraft. Each tape i s generated by

stacking seven short data tapes received f rom Goddard Space Flight

Center on a 2400 foot reel. The stacked tapes were written on an

IBM 360140 system. They contain external BCD characters written

in 7 t rack mode in even parity at 800 char/ in density.

The f irs t file on each stacked tape i s a one record file which

serves a s an index to that tape. The physical record (gap to gap) i s

865 characters long and can contain 72 twelve character logical

records, There i s one index entry for each of the seven GSFC short

ree ls stacked on the larger tape. The remaining 65 entries a r e not

used. The entries a r e in the following format:

Chars P

1-6 GSFC ree l number

7-9 Number of files contained on the GSFC tape

10-12 Blank

Following the index file i s the stacked experiment data copied

f rom the GSFC reels. The data i s in the same file by file format

a s it appeared on the original tapes except that a 12-character field

has been prefixed to each record to identify it to UC programs using

these tapes* The individual records a r e 865 characters (incl~tding

prefix f i e ld ) and are fornrrzitted as follows:

Chars

1-6 T h e GSFC r e e l n u m b e r on which this record

o r i g i n a l l y appeared

7- 9 The file number within that GSFC ree l

10-12 The record number within the above file

13-864 The experimental data in its original format

(see "AIMP Stacked Data Tape Format" belowl.

The las t f i le on each of the GSFC tapes is a one record file

with the twelve character identification field (i, e., Satellite No. ,

Month, Day, etc.) se t t o nines. This file has also been copied onto

the stacked tape. Thus the f i r s t record of the following file on the

stacked tape will have a different GSFC ree l number and a file number

of 1 in the prefix field. Two end-of-file m a r k s will follow the l a s t

valid data file on the stacked tape. Figure 15 shows the tape structure.

Tape Chars

P1 Original GSFC ree l number 6

P 2 Fi le number within GSFC r e e l 3 Pref ix fields

P3 Record number within above file 3

1 Identification (ID)

(a) Satellite 2

(b) Julian Day of Year 3 ID fields

( c ) Year 2

(d) Dada Acquisition Station 2

( e ) Analog Tape Number 3

E 6 F E Q F

72 TWELVE C H A R A C T E R LOGICAL RECORDS

E O F

FlLE I

RECORD 1

F l L E t RECORD 2

FlLE I C---------

RECORD N

EOF

2

ORD I

TAPE STRhlCT'URE

F i g u r e 15

Tape Cha r s

2 A I D Line Indicator 1

3 T i m e f o r t he Middle of Channel @, F r a m e (a) Day Count of Year (Jan. 1 = 0) 3

(b) F rac t i ona l Day of Year (Mill isecond P rec i s ion ) 8

(c) Blank 1

4 T ime F l ag 2

5 Sequence Counter ("Satellite Clock") (1 Decimal Number) 6

6 F r a m e Rate 4

7 Sequence Identification 1

I t ems 8 through 23 repea ted two (2) t i m e s per sequence, i. e . , f o r f r a m e s 5 and 13.

F r a m e Number

P r e Data F l a g

Raw Data (4 Comb F i l t e r Numbers)

Guardband F l a g

Converted Data (1 Decimal Number of max. 65, 535) (GM1)

Raw Data (4 Comb F i l t e r Numbers )

Guardband F l a g

Converted Data (1 Decimal Number .of mqx. 65,535) (IC Clock)

Raw Data (4 Comb F i l t e r Numbers)

Guardband F l a g

Converted Data (1 Decimal Number of max. 65,535) (GM2)

Raw Data (1 Comb F i l t e r Number)

Raw Data (3 Comb F i l t e r Numbers ) (IC Redundant)

Guardband F l a g

Converted Data (1 Decimal Number of rnax. $095) (PC Count)

Post Data Flag

Data Qua l i t y F lag

Pe r fo rmance P a r a m e t e r ( I Decimal Number of max, 255)

2 Data f ie lds

1

12

1

I t em P

Tape C h a r s

26 Pe r fo rmance P a r a m e t e r (1 Decimal No. of Max. 255)

27 P e r f o r m a n c e P a r a m e t e r (1 Decimal No, of Max. 255):;

28 Optical Aspect

(a) Pseudo Sun Pu l se F l a g 2

(b) Sun Angle (1 Octal No. of Max. 7778) 3

(c) Spin Pe r iod (1 Decimal No. of Max. 4095) 4

(d) Sun T ime (1 Decimal No. of Max. 4095) 4

(e) Moon Time 1 (1 Decimal No. of Max. 4095) 4

(f) Moon Time 2 (1 Decimal No. of Max. 4095) 4

(g) Moon T ime 3 (1 Decimal No. of Max. 4095) 4

TOTAL NUMBER O F CHARACTERS P E R SEQUENCE 223

F o u r of the above descr ibed sequences a r e blocked together with t he exception that the l a s t t h r e e (3) sequences of the block do - not contain the prefix f ie lds ( I tems P1 , P2 , P3 ) and the Identification (ITEM #1) o r A / D Line Indicator (ITEM #2) t o make a tota l of 865 BCD c h a r a c t e r s pe r block.

NOTE 1: Fill data fo r i t e m s 12, 15, 18, 22 i s indicated by 9 ' s

throughout the field.

NOTE 2: Optical Aspect and Pe r fo rmance P a r a m e t e r s t ab les will

be made available t o invest igators upon request .

I n a Sequence 1 I t em #25 will be P P 1 , I t e m #26 will be P P 2 , Lkem #27 will be PP7 ,

In a Sequence 2 I t em #25 will be P P l 4 , Item #26 will be PP15 , I t em #27 will be PP16,

In a Sequence 3 I t em #25 will be PP1'7, I t e m #26 will be PPL8, Item #27 will be PPL9,

In a Sequence 4 Itern #25 will. be PP20, Item #26 will be P P Z 2 , Itern #27 will be PPZ4,

NOTE 3 : R a t e Caleu-Sations

A , GMl and GM2 r a t e s

1. "S" Mode

i f N < 32768 ("T" Bit = 0)

2. "T" Mode

i f N > 32768 ("T" Bit = 1) Then N = N - 32768

and

- 32768 Ro - '- (N/800)] K

Ro: GM1 (or GM2) r a t e i n pulses per second.

N: The GM1 (or GM2) accumulator value - -

15 l ea s t significant bits .

K: T ime base cor rec t ion fac tor

F R - F R K = - - --- NFR 5926

FR: Actual f r a m e r a t e f r o m data.

NFR: Nominal f r a m e r a t e in f ract ional par t of a

day.

5.12 s e c NFR = 60 x 60 x 24 = 0.00005926 day

B. Ion Chamber r a t e calculations

1. SCCLK ra t e - - Interval method

a. Equations

No t 1

( I ) Ri =

Ri: The ion chamber rate in pulses per s e c o n d ,

Nl: The 1as"i:CGLM valut- ! preceding the presen t

value.

N2: The presen t ICCLK value 1

No: The number of ICCLK values that have been

1 ' s between the N1 and N2 values.

NZ: The number of ICCLK values which have been

0 ' s o r 1 ' s between the N1 and N2 values.

K: The t ime base cor rec t ion fac tor ( see pa r t A

of Note 3) .

b. Conditions fo r use of in terval method: use

equation (1) i f two p a i r s of values ex i s t such

that ICCLK > 1 and ICCNT = 0 o r 1 - Use equation (2) if ICCLK > 1 and ICCNT 2 2.

If none of the above conditions exis t , then the

in terval method cannot be applied.

c. Notes fo r in terval method.

1) The sequence count i s used to determine

NZ"

2) If e i t he r a "gap" o r "invalid data" occur

between N1 and N2 then a n ICCLK value of 0

m a y be a s sumed f o r that readout o r readouts .

"gap": One (1) or m o r e mi s s ing sequence of data,

"invalid data": Non-numeric IGCLK value o r ICCLK value of a l l 9 ' s .

3) Each tape file is to be considered as an

independent set of XGCLK and IGCNT

values fo r the in te rva l calculations.

2, ICCNT r a t e - - Count method

If ICCNT > 10

- Nc R c - 39.680K

otherwise the count r a t e i s not computed and i s

left blank i n the print-out.

Rc: ICCNT r a t e in pulses pe r second.

Nc: ICCNT accumulator value (on tape).

K: The t ime cor rec t ion fac tor ( s ee par t A of

Note 3 ) .

111, A M P - 1, 2 MAJOR COMPUTER PROCESSING PROGRAMS

The following is a brief descr ipt ion of the ma jo r computer p r o -

g r a m s used to p r o c e s s the Universi ty of California AIMP-1, 2 sa te l l i te

data:

1. AIMP-RATE

The AIMP-RATE p rog ram s e r v e s a s the p r i m a r y "raw"

printout on a production ba s i s f p r AIMP data. About

one-half of the printout is dumped f r o m the tape. The

remaining printout i s the r e su l t of r a t e calculations for

the t h r ee exper iment de tec tors , performance pa rame te r

calculat ions, and other miscel laneous i tems.

The p r o g r a m was wri t ten by Ba rba ra Watson fo r the IBM

7094 in July, 1966.

2. PLOT24 -- The PLOT24 p r o g r a m produces a one- inchlhour five cycle

semi- log plot of the two GM outputs and the ion chamber .

This plot s e r v e s a s the p r i m a r y display of the AIMP

exper imental data.

The p r o g r a m was completed by Mar i a Rober t s fo r the

IBM 7094 in October, 1966 and l a t e r modified f o r the

CDC 6400 in July, 1967.

3 . LSEP

LSEP i s the p r o g r a m used to p roces s ASMP orb i t t r a j ec to ry

tapes on a production bas i s , It ca lcula tes and l i s t s orbi t

t r a j ec to ry p a r a m e t e r s re levant to " c h e Universi ty of California

exper iments , Two a l te rna te vers ions exist , PELSEP l i s t s

p a r a m e t e r s re levant to the lunar orbi t of A W P - 2 , P,ILSEP

l i s t s p a r a m e t e r s relevant to the e a r t h orbi t of ASMP-1.

The program w a s wr i t t en b y Barbara Watsorz for the IBM

7094 in J u l y , 1967 and l a t e r modified f o r the CDC 6400

by G. Pit t .

4. AIMP-OTPLT

Th i s p r o g r a m plots values of sa te l l i te d is tance in Re and

LSEP and MLAT i n deg ree s f o r a 24-hour period. The

input is f r o m AIMP o rb i t t r a j e c to ry tapes . The t i m e ax i s

is 24 inches long and cor responds wi th the 1- inchlhour

data plots.

The p r o g r a m was wr i t t en by B a r b a r a Watson and George

P i t t i n August, 1966 f o r the IBM 7094. It was l a t e r modi -

f ied f o r the CDC 6400.

5. AIMP-AVRATE

Th i s p r o g r a m calcula tes co r r ec t ed r a t e s and average

c o r r e c t e d r a t e s f o r the AIMP GM de t ec to r s , obse rved count

and clock r a t e s f o r the Ion chamber and ca lcu la tes

va r ious s p e c t r u m p a r a m e t e r s .

The p r o g r a m w a s wr i t t en by George Pitt in August , 1966

f o r the IBM 7094 and l a t e r modified fo r the CDC 6400.

6. AIMP STACK SYSTEM

The AIMP STACK SYSTEM i s an in tegra ted s y s t e m of p ro -

g r a m s designed t o mainta in AIMP sa te l l i t e data t apes in

convenient, compact f o r m and faci l i ta te the manipulat ion of

individual data tape s,

'The programs were w r i t t e n in Ju ly , 1966 b y Mar ia Rober t s

fo r the IBM 360139,

IV , LIST OF PUBLICATIONS REPORTING RESULTS FRBM THE EXPLORER 3 3 & 35 SATELLITES

I , Observat ions of so l a r f l a r e e lec t rons in in te rp lnae ta ry space , R,P, Lin, PHE) Disser ta t ion, Phys i c s Depar tment , Vnivers i ty of California, Berkeley, August, 1967

2. Corre la t ions of so la r - f l a re e lec t ron events with rad io and x - r a y emi s s ion f r o m the sun, R, P. Lin, Canad. J. Phys. 1968

3. Observat ions of bow shock and ups t r eam energet ic e lec t ron spikes , K. A, Anderson, Book of s u m m a r i e s and ~ b s t r a c t s , ~ n t e r n a t i o n a l Symposium on Phys i c s of the Magnetosphere, Washington, D. C . , 1968

4. Observat ions of lunar shadowing of energe t ic par t ic les , R. P. Lin, J. Geophys. Res. - 73, 3066, 1968

5. So la r f l a r e injection and propagation of lovr-energy protons and e lec t rons i n the event of 7-9 Ju ly 1966, R. P. Lin, S. W. Kahler and E.C. Roelof, Solar Phys . - 4, 338, 1968

6. Observat ion of in te rp lane ta ry f ie ld l ines i n the magnetotai l , K. A. Anderson and R . P , Lin, J. Geophys. Res . 74, 3953, 1969 -

7. E l ec t rons and protons in long-lived s t r e a m s of energet ic so la r par t i c les , K.A. Anderson, Solar Phys . - 6, 111, 1969

8. Energe t ic e lec t rons of t e r r e s t r i a l o r ig in behind the bow shock and u p s t r e a m in the so l a r wind, K. A. Anderson, J. Geophys. Res . 74, 95, 1969 -

9. Relation of energet ic par t i c les i n the p lasma sheet to the au ro ra l zone, K. A. Anderson, , ed, by B.M. McCormac and Anders Omholt, Van Nostrand Reinhold Pub, Co. ,

10. The so l a r par t ic le event of Ju ly 16-19, 1966 and i t s possible a s soc - iat ion with a f l a r e on the invisible s o l a r hemisphere , H. D. P r i n c e , E. R. Hedeman, S, W, Kahler and R. P. Lin, Solar Phys. 6, 294, 1969 -

11.. Spatial gradients of energet ic protons and e lec t rons observed a f te r the 7 July 1966 so la r f l a re , S.W. Kahler and R e p . Lin, Annals of t he IQSY, 9

h4,I.T. P r e s s , Ca

12, Method to determine s ense and magnitude of e l ec t r i c f ield f r o m luna r par t i c le shadows, K, A, Anderson, 5, Geophys, Res . 75, 2591, 1950 -

13, Observat ions of s ea t t e r - f r ee propagation of -40 KeV 80la , r e lec t rons i n the in te rp lane ta ry medium, R,P, Lin, J, Gzophys, Res , 75, 2583, l970 -

14, The emiss ion and propagation of -40 KeV so l a r f l a r e e lec t rons , I. Relationship of ~ 4 0 KeV e lec t ron to energet ic proton and re la t iv i s t i c e lec t ron emiss ion b y the sun, R. P, Lin, Solar Phys . 12, 266, 1970 -

Explorers 3 3 and 35 Publications List page 2

15. A layer of energet ic e lec t rons (> 40 keV) near the magnetopause, C.I. Meng and K.A. Anderson, J. Geophys. Res . - 75, 1827, 1970

16. The emiss ion and propagation of ~ 4 0 keV so l a r e lec t rons , R . P . Lin , Acta Phys ica Academiae Sc ien t ia rum Hungaricae 3, Supp. 2, 669, 1970

17. So la r and galact ic cosmic r a y s and the in te rp lane ta ry magnet ic f ie ld 28 January-25 F e b r u a r y 1967, S. T. Lindgren, Acta Phys ica Academiae Sc ien t ia rum Hungaricae 2, Supp. 2, 1970

18. The emiss ion and propagation of ~ 4 0 keV so l a r f l a r e e lec t rons , LI. The e lec t ron emi s s ion s t ruc tu r e of l a rge active regions , R.P. Lin, So la r Phys . , i n p r e s s

19. Energe t ic e lec t rons in the magnetotai l a t 60 R C. I. Meng, J. e' Geophys. R e s , , in p r e s s

20. A theoret ical t r e a tmen t of l una r par t ic le shadows ( P a r t I), R. E. McGuire, t o be submitted to Cosmica l Elect rodynamics

21. The acce le ra t ion and emi s s ion of 10-100 keV e lec t rons by so la r f l a r e s , H. S, Hudson and R. P. Lin, i n preparat ion

V. PAPERS PRESENTED A T SCIENTIFIC MEETINGS REPORTING

RESULTS FROM THE EXPLORER 33 & 35 SATELLITES

1. Observat ions of so l a r f l a r e e lec t rons , R, P. Lin, Tenth Internat ional Conference on Cosmic Rays , Calgary, Canada, 1967

2. P r o b l e m s connected with so la r par t ic le events - - par t ic le physics , K. A. Anderson, ESLAB /ESRIN Symposium, Noordwijk, Holland, 1967

3. P r e l i m i n a r y r e su l t s of the energe t ic par t ic le exper iment on Explore r 33, R. P. Lin, R e J. Pao l i and K. A. Anderson, Amer ican Geophysical Union Annual Meeting, Washington, D. C., 1967 (in T rans . AGU 48, - 160, 1967)

4. So la r e lec t ron events 1964-1967, R.P. L in and K.A. Anderson, Midwest Cosmic Ray Conference, Iowa City, Iowa, 1968

5. The s o l a r par t i c le events of May 23 and May 28, 1967, S, T. Lindgren, Midwest Cosmic Ray Conference, Iowa City, Iowa 1968

6. Energe t ic e lec t rons of t e r r e s t r i a l o r ig in at 60 Re geocentr ic d is tance, K. A, Anderson, Amer ican Geophysical Union Annual Meeting, Washington, D. C . , 1968 (in Trans . AGU e(l), P 968)

7. Effects of the moon on energet ic so l a r protons and e lec t rons , R. P. Lin, Amer i can Geophysical Union Annual Meeting, Washington, D, C. , 1968 (in Trans . AGU 49(1), 1968)

8. Luna r shadowing of so la r and t e r r e s t r i a l e lec t ron fluxes, R. P. Lin, Amer i can Geophysical Union National F a l l Meeting , San F r a n c i s c o , California, 1968 (in T rans . AGU - 49(4), 1968)

9. Observat ions of 3 - t o 10-MeV protons i n energe t ic s t o r m par t i c le events, S. W. Kahler , Amer ican Geophysical Union Annual Meeting, Washington, D O C . , 1968 (in Trans . AGU 49(4), 1968)

10. The r e c u r r e n t proton events of June 24 and September 27, 1966, S.W. Kahle r , AAS Specia l Meeting on Sola r Astronomy, Tucson, Arizona, 1968

11. E l ec t rons f r o m so l a r f l a r e s , K,A. Anderson, Amer i can Phys i ca l Society Meeting, Miami, F lor ida , 1968

12, E lec t rons and proaons i n long-lived s t r e a m s of energet ic s o l a r par t i c les , K, A, Anderson, -&AS Special Meeting on Solar Astronomy, Pasadena , California, 1969

13. E n t r y of so l a r cosrnic r a y s into the earth." magnetosphere , K. A, Anderson, Su e r Advanced Study Insti tute, E a r t h ' s P a r t i c l e s and F i e ld s , Santa Ba rba ra , California, 196 9

P a p e r s P re sen t ed at Scientific Meetings Repurfiing Explore r 33 & 35 Resul ts Page 2

14. Energet ic e lec t rons a t the magnetopause, i;, I, Iaeng, Sunamer Advanced Study Insti tute, E a r t h ' s P a r t i c l e s and F ie lds , Santa Ba rba ra , California, 1969

15. So la r par t i c les and re la ted so l a r phenomena, KiA. Andhrson, XI h t e r n a t i o n a l Conference on Cosmic Rays , Budapest, Hungary, 1969

16. High energy par t i c les i n the e a r t h ' s magnetotai l , K.A. Anderson, IAGA Meeting, Madrid , Spain, 1969

17. Energet ic par t i c les in the magnetotai l , K. A. Anderson, Amer i can Geophysical Union Annual Meeting, Washington, D. C. , 1969 (in T rans . AGU - 50(4), 1969)

18. The e a r t h ' s magnetosphere , K. A. Anderson, Sixteenth Annual West Coast R e s e a r c h Rese rve Seminar , T r e a s u r e Island, San F ranc i s co , California, 1969

19. P a r t i c l e shadowing by t he moon, K. A. Anderson and R. P. Lin, Amer ican Geophysical Union Annual Meeting, Washington, D. C. , 1969 (in T rans . AGU 50(4), 1969)

20. Simultaneous x - r a y and e lec t ron emi s s ion f r o m the sun, H.S. Hudson and R. P. Lin, AAS Specia l Meeting on Solar Astronomy, Pasadena , California, 1969

21. Halo s t ruc tu r e of so l a r proton events , S.W. Kahle r , R . P . Lin and E , C. Roelof, AAS Special Meeting on Solar Astronomy, Pasadena , California, 1969

22. F luxes of ~ 4 0 keV e lec t rons assoc ia ted with so la r active regions , Re P. Lin, Amer i can Geophysical Union Annual Meeting, Washington, D. C., 1969 ( in T rans . AGU - 50(4), 1969)

23. The emis s ion of -40 keV e lec t rons by the sun, R .P , Lin, AAS Special California, - 1969

24. Coronal s to rage and in te rp lane ta ry propagation of low energy so l a r par t i c les , E.C. Roelof and R.P. Lin, Amer ican Geophysical Union National F a l l Meeting, San F ranc i s co , California, 196 9 ( in T r a n s . AGU - 50(11), 667, 1969)

25. A l aye r of energe t ic e lect rons (> 40 keV) n e a r the magnetopause, C,I , Meng, Amer i can Geophysical Union Annual Meeting, Washington, D, C , , 1970 ( in Trans , AGU - 51, 1970)

26, The emission and prop;zga"cion of m40 keV s ~ L a r electrons, R, P, Lin, X I International CTorSerence on Cosmic Rays, Budapest, 1369

P a p e r s Presented at Scientific ~'VIeetlngs Repor t~ng Explorer 3 3 & 35 Resuits Page 3

27 , Solar and gala,ctic cosmic rays and the interplanetary magnetic fieid 28 January-25 February 1967, S. T. Lindgren, Eleventh International Conference on Cosmic Rays, Budapest, 1969

28. Fluxes of ~ 4 0 keV electrons associated with solar active regions, R. Po Lin, International Symposium on Solar -Te r res t r i a l Physics, Leningrad, USSR, 1970