U. of Iowa 65-36

Observations with University of Iowa Equipment on Mariner I V

m y - October 1965 (Preliminary Report )*

S . M. Krimigis, J. A. Van Allen, and L. A. Frank

25 October 1965

* Development of equipment was supported i n p a r t by contract

with J e t Propulsion Laboratory 950613; reduction of data i n p a r t by National Aeronautics and Space Administration under Grant NsG 233-62.

in part- Thb work WPB pmformed~or the Jet Propulsion L a w , California Ins+it*+e of Technology, .sponsored by the National Aeronautics and Space Administration un&4 Contract NAS7-100.

https://ntrs.nasa.gov/search.jsp?R=19660009910 2018-07-19T09:27:49+00:00Z

1

1. Introduction

This report continues the presentation of measurements made

with the Trapped Radiation Detector on Mariner IV. For a,descrip-

t ion of the experimental apparatus, the scient i f ic objectives, and

some early results, one should refer t o University of Iowa Research

Report 65-5 of 22 February 1965 [Van Allen, Dimigis, and Frank,

19651.

[Van Allen e t al., 1965a] summarizes some of the resu l t s obtained

i n the period February-May 1965, and discusses the possibi l i ty of

detection and measurement of the Martian magnetic moment w i t h the

Trapped Radiation Detector. A detailed discussion of the Martian

encounter measurements has been given elsewhere [Van Allen e t al.,

1965bl. The present writing i s mainly concerned w i t h the inter-

planetary resu l t s and i n particular w i t h those obtained from the

beginning of May t o October 1, 1965, on which date the transmission

of data was terminated.

In addition, University of Iowa Research Report 65-15

2

2. Operation of Equipment and Data Reduction

A l l four University of Iowa detectors continued t o function

properly through October 1, 1965, on which date the present phase

of the Mariner I V mission ended. The temperature of the package has

declined gradually and i n the expected m e r from the f l i gh t maximum

value of 29.4" C on day 334 of 1964 t o 9.3' C on day 267 of 1965.

The f ac t t ha t the experiment was shut off during picture playback

a f t e r encounter appears not t o have caused any deterioration i n

detector performance.

The data analysis up t o the present time has been done by

using the Jet Propulsion Iaboratory' s "user's program" listings.

From these preliminary data the folluwing papers have been or are

i n the process of being published:

(1) J. A. Van Allen, Absence of 40 keV Electrons i n the

Earth's Magnetospheric Tail a t 3300 Eiarth Radii, J . Geophys . R e s ., E> 4731-4739, 1965.

(2) J. A. Van Allen, L. A. Frank, S. M. mimigis, and

H. K. H i l l s , Absence of M a r t i a n Radiation B e l t s and Implications

Thereof, Science, - 149, 1228, 1965 . (3) J. A. Van Allen and S. M. mimigis, Impulsive miss ion

Of - 40 keV Electrons frm the Sun, J. Geophys. Res., - 70, December,

1965

3

In addition, the following paper was orally presented at the

American Geophysical Union meeting i n Dallas, Texas, September l-3>

1965 :

J. A . Van Allen and S. M. KWrtigis, Interplanetary and Martian

Particle Measurements with Mariner IV, Trans. American Geophysical.

- - Union, 46, No. 3, 532, 1965 (Abstract).

A t the time of the present writing, three Master Data Library

(MDL) extract tapes have been received fram JPL covering days 333-340

and 340-347 of 1964 and days 032-039 of 1965. The quality of the

data i s satisfactory and further tapes are awaiting processing on the

University of Iowa IBM 7044 computer system.

I ‘ I

1 1 1 I

4

3. Solar Events During May-October 1965

' (a) General Remarks

In Figure 1, the d a i l y averages of detectors D1 and D2

have been plotted f o r the entire period of the Mariner I V f l i g h t .

It i s observed t h a t since the beginning of May, the frequency of

low energy solar proton events has increased considerably, compared

t o the November 28, 1964 - A p r i l 1965 period. It is necessary

a t t h i s point t o define what constitutes an "event", -since the

c r i t e r i a for distinguishing different events i s somewhat subjective.

A solar event i n th i s study i s defined as a s t a t i s t i ca l ly

significant departure of the counting rate of the detector from i t s

background level and an eventual return t o th i s level after a specified

period of time, which may vary from a few hours t o a f e w days. A

clear resolution in to dis t inct events is smetimes d i f f i cu l t due t o

complex intensity-time profiles.

Figure 2, where the increase which began on day 163 continued on

t o day 170; i n the qpinion of the authors, two events are involved,

the f irst one on days 163-165 and the second one on days 166-170

A case in point i s shown i n

The various separately identified events and other relevant

I

5

I

information are l i s t ed in TElble I.

are apparent:

The following general features

(1) A t o t a l of 24 solar events has been observed, 22 of which

occurred during the l a s t 5-l/2 months of the approximately 10-month

period of observations.

(2) For the first time, three "pure" electron events were

observed i n association w i t h phenomena on the sun; i n addition, one

event was seen which contained an admixture of protons and electrons.

.

(3 ) It i s seen f rm the last column of Table I that as the

Earth-Sun-Probe (ESP) angle increased, it became increasingly d i f f i cu l t

t o find a plausible correlation between events on the sun and par t ic le

observations at the position of the spacecraft.

(4) Except for the event of February 5, the maximum flux in

the proton events i s much less than the typical flux observed ear l ie r

i n the solar cycle.

(5) Occurrence of the events appears t o be independent of

s o l a r rotation.

Iet us naw examine same of the major resu l t s i n de ta i l .

-. .

6

(b) Electron Events

In Figure 2 the counting rates 105 a l l University of Iowa

On detectors i n Mariner I V are plotted fo r days 145-175, 1965.

day 145, there i s a large increase i n the counting rates of

detectors A and B, with no indication of an acccanpanying enhance-

ment i n the rates of detectors c, D1, and D2.

properties of the five detectors one concludes that the par t ic les

which caused the increase must be electrons of energy > N 40 keV

[Van Allen and XTimigis, 19653 . event occurred on day 156, and another on day 164.

time profiles exhibit abrupt onsets, increases t o maximum values i n

times of the order of a f e w hours, and gradual declines over periods

of one t o two days.

those seen i n solar proton events for proton energies of the order of

tens of MeV. It appears t h a t these electrons are emitted impulsively

from the sun at approximately the same time as are bursts of radio

noise and x-rays observed by others w i t h t e r r e s t r i a l equipment.

By combining the

A similar, although l e s s intense,

The intensity-

These profiles a re morphologiccdly the same a s

mese electrons propagate diffusively i n interplanetary space,

although the i r behavior appears t o be significantly different than

that of energetic protons, i n that the i r diffusion coefficient appears

t o be independent of heliocentric r a d i a l distance [ c f . XTimigis, 19651 .

I

7

It i s estimated that about electrons E > 40 keV were

A i t t e d on May 25 and on June 5, and about e -

on (Tune 13. Such

electrons constitute a new tool for study of the structure of' the

interplanetary magnetic field and fo r discussion of solar flare

physics [Van Allen and mimigis, 19651.

(c ) proton Events

In Figures 2 through 4, four-hour averages of the detector

counting rates have been plotted f o r days 145 t o 274 of year 1965.

We shall concentrate our attention on detectors D and D since

they are the most sensitive ones, due t o the i r l o w background

counting rate; i n addition, the par t ic le identification i s conclu-

1 2'

sive since they are insensitive t o electrons.

(as l i s ted in Table I) were identified by use of the c r i t e r i a given

The proton events

ear l ie r i n section (a ) .

stayed above background about 40$ of the time during the period of

It is seen that the counting r a t e of 9

observation.

on the sun as seen frm earth is tenuous a t best, and could be m i s -

leading, especially at large ESP angles. This i s par t ly due t o the

f ac t that the par t ic le intensit ies are low, and that t h e propagation

mechanism ( i f the particles are of solar origin) appears t o be that

The association of' a particular event w i t h ac t iv i ty

8

of mass motion rather than free diffusion i n a hamogeneous medium.

The intensity-time profiles shown in Figures 2-4 d i f fe r

considerably frm those of protons whose energies are in the tens of

MeV.

The only event which approaches the "typical" proton event occurred

on days 152-156, with a sharp onset and a slow decay; it i s probable

The onset of an event i s usually very slaw as i s the decay.

'that a diffusion model calculation w i l l adequately describe the

The event on days 218-221 intensity-time prof i le in t h i s case.

appears t o be of particular interest; the r i s e i n intensity occurred

i n about three days, whereas the decay from maximum took place i n

l e s s than a day. This behavior i s exactly the opposite of that

expected i n a "typical" event; it suggests that the abrupt decay

may be a spat ia l rather than a time variation and thus implies dis-

continuities i n the medium with a scale of - 10 lan. 6

(d) Interpretation

We have seen that more than 90s of the events in the period

28 November 1964 - 1 October 1965 occurred a f t e r the beginning of

May, when the spacecraft was a t heliocentric distance > 1.4 A.U.

It was a l s o noted that it is very d i f f i cu l t t o establish one t o

one correspondence between f l a re s on the sun and par t ic le increases

9

a t the position of Mariner I V .

the majority of cases, no sudden commencement was observed at the

earth.

the frequency of occurrence of the events; t h i s has been done in a

preliminary manner and the results indicate that there is no single

27-day period encanpassing all cases, but rather a number of 27-day

periods under which certain events can be grouped; for example,

the events on days ll0, 163-165, 191, 218-221 constitute such a

grouping.

addition, a camparison of the occurrence of these events can be made

w i t h the particular sector of the interplanetary magnetic f i e ld

i n which the spacecraft l i e s [Wilcox and Ness, 19651; such a study

can be effected by ccxnparison of the magnetometer da ta and the

par t ic le data froan the respective experiments on Mariner I V .

From Table I it is seen that i n

One can e d n e the data for a possible 27-day period i n

Further study along these l ines is now in progress. I n

With the foregoing remarks i n mind, one may raise a question

as t o the origin of the observed protons. Were the protons indeed

produced at the sun or d id they acquire the i r observed energies i n

interplanetary space? If the former i s true, then the increase in

ac t iv i ty since l a t e &ril could be taken as the beginning of the new

solar cycle.

thermal) par t ic les i n sufficiently agitated plasmas has been observed

O n the other hand, the generation of energetic (non-

w . .. ,

10

in the laboratory, The lnter@,axmtsry medium may be conaidered ruch

a plasmr 4itated by solas activity, Such a suggestion ha8 a3ready

been mde by Perkor [l9653 9~ Marinor obrervatlonr may conrtitute

11

4 . Long Term Rates of Detectors A, B, C

I n Figure 5 are shown the da i ly mean counting r a t e s of the

three Geiger tubes A, B, and C, omitting the high i n t e n s i t y of the

e a r l y February event and the proton and e lec t ron events l a t e r on.

Data are shown up t o day 196.

declined by about 13% from day 340 of 1964 t o day 196 of 1965 and

t h a t the r a t e of B has declined by about 10% (although i n a

d i f f e ren t manner) over the same period. The rate of C has remained

r e l a t i v e l y unchanged up t o day 145 and has since declined gradually

It appears t h a t the r a t e of A has

by about 5%.

The decline i n the r a t e of A appears t o be a temperature

e f f e c t , as shown by environmental t e s t i n g performed a t JPL and

evaluated a t the University of Iowa.

rate of B i s not understood a t present .

(more shielded from low energy p a r t i c l e s ) i s more representat ive

of t he cosmic ray background.

The change i n the counting

The rate of detector C

I ts counting r a t e w i l l be corrected

f o r time var ia t ions and used t o determine a possible he l iocent r ic

gradient i n ' t h e cosmic r a y i n t e n s i t y between Earth and Mars.

The da ta f o r days 215-274 have been computed and fur ther declines

i n the counting r a t e s of a l l detectors a re present . The da ta

i 8 4 I

I I t 'I

12

w i l l be examined i n de ta i l when the complete records from the MDL

tapes have been received.

I I 1 I I I

. .

13

REFERENCES

Krimigis, S. M., An Interplanetary Diffusion Model f o r the Time

Behavior of In t ens i ty in a Solar Cosmic Ray Event,

J. Geophys. Res., - 70, 2943-2960, 19650

Parker, E. N., In terplanetary Origin of Energetic Par t ic les ,

Phys. Rev. Letters, - 1 4 , 55-57, 1965-

Van Allen, J. A . , L. A. Frank, S. M. Krimigis, and H. K. H i l l s ,

Observations with University of Iowa Equipment on

Mariner IV--February, March, April, May 1965 (Preliminary),

U. of Iowa Research Report 65-15, 24 May 1965.

Van Allen, J- A., L. A. Frank, S. M. Krimigis, and H. K. H i l l s ,

Absence of Martian Radiation Bel ts and Implications Thereof,

Science, - 149, 1228-1233, 1965.

Van Allen, J. A . , and S. M. Krimigis, Impulsive Emission of - 40 keV Electrons from the Sun, J. Geophys. Res., -9 70

December 1965.

Van Allen, J. A . , S. M. Krimigis, and L. A. Frank, Observations

w i t h University of Iowa Equipment on Mariner I V November

1964--February 1965 (Preliminary Report), U. of Iowa

Research Report 65-5, 22 February 1965.

Wilcox, J. M., and N. F. Ness, A Quasi-Stationary Co-Rotating

Structure i n the Interplanetary Medium, Goddard Space

F l ight Center Report X-612-65-302.

I

I I

I I I I I I I I

I I

i

I-=== s N

0 N N

E

P

s

3 f

> !

, ,

8 I

Et \

4 1 I I I I I I I I I I I I I

AT r - 1.5 A.U. DURING MAY 25- JUNE 23.1965 E S P = 45'

SOLID LINES INDICATE WE-EVENT BACKGROUND RATES

8 30-

=- 0 z w \

z - 3 0 c'

8 1.0-

p a5-

50-

20 n

DETECTOR A - PROTONS- E p L 6 7 0 t 3 0 K ~ V ELECTRONS - E, 2.45 KeV

I

.*I

. *

= I -**, m---1.+.

- -

DETECTOR B - PROTONS- E p 8 5 5 0 i 2 0 KeV . - - ELECTRONS- E e L 4 0 KeV - -

- -

-

DAY OF YEAR 1965

w - m - \

p z - 3 0 0

1.0

0.5

- - - L.0.S. . 5-.

a5-- - -

- I - - - DETECTOR D, - PROTONS 0.505 E p r I I MeV - - - -

I , ! ' * . ELECTRONS-EFFICIENCY< 1x10 ' -

- -

- - - -

I - **it*

'f

c 0

a2-

z * * t

I 1. 1 I I I I 1 I I I I I I I 4

1 SOLAR PROTON EVENTS OBSERVED WITH MARINER IV

E.S P-48" AT r -1.5 A.U. DURING JUNE 23 - JULY 15.1965

.SOLID LINES REPRESENT BACKGROUNO CQUNTlNG RATES ON DAYS !35- 145

1.0 I- * I I I I EeZ150 KeV

DETECTOR C -Ep?3.1 MeV

0.7

0.5

1.0

0.6

1.0

0.7

0.5

I I

1

FIGURE 3

I' I 1 i I I 1 1 I I I I I 1 I I

8-22 Jarmr~

5-13 P e b W

20 April

6-8 w 25-28

26 my

27 my

1-5 m e

5-7 Sue

1z-14 June

13-14 SUne

15-20 June

21 June

28 m e 4 July

2-3 July

4-6 Julv 10 July

13-15 July

m meemtion. 15 July-3 A w s t

3-4 A"8x.t

6-9 A w s t

17 August

2631 m s t

m meemtime 1-3 S e p t d r

22-24 Septslber

25-27 SCpt-hr

ny Iws

au

36-44

ll0

226228

145-148

146

147

152-156

156158

163-165

161-165

166-170

1P

179-182

183-1&

185-187

191

194-196

196215

215-216

218-221

23

238243

243-245

265-267

268270

Eel laodric R a d i a l mstaoee

[A.II.)

1-055

1.140

1.383

1436

1.480

1.480

1.480

1.495

1.502

1,514

1.514

1.521

1.529

1.539

1.542

1.j4j

1.550

1.554

1.567

1.569

1.572

1.573

1.565

1.563

Eouth-Sun-Pr&be A @ g h (Wgretsl

+ 1.8

- 1.3

-24.5

-30.9

-40.2

-40.2

-40.2

-43.6

-45.4

-48.7

-48.7

-50.9

-53 2

-57.0

-58.4

-59.4

-62.0

-64.3

-73.9

-76.43

-80.97

-ea.ll

-1w.o

-101.56

4.3 2 0.3

140

0.4 2 0.1

0.74 2 0.2

eo

0.9 2 0.3

1.1 2 0.3

3 2 0.2

58

1.1: 0.2

5

1.7 2 0.5

0.6 2 0.2

4.2 + 0.2 -

1.1 2 0.2

2.1 + 0.2

0.38 2 0.1

6.4 2 0.3

1.4 2 0.2

6.6 2 0.3

0.4 2 0.1

6 2 0.3

0.8 2 0.2 0.54 2 0.1

Rrtinent solar Activitr As Seen Rrm Earth

C l l l B l l 2 flure 6 san., 0810 w c h s e 2+ r m 5 Feb . , 1750 W

class 2 riare 16 April, 0915 W

m e reported

contin- 25 Hay, 2241 VI

ciaas 1 r m 25 Hay, 2240 W

m e

rype IV 5 June, 1825 WP

Class 2+ iUve 9 . m e , 0600 VI

i&ne reparted

class 2 IlnR 15 ,J"", 0736 VI

clam I+ flere 18 June, ogol m

28 June, 1mo W Clas. 21 flure

m e

. None

ClhS8 1+ Ilarr 9 0547 W

m e

m e

None

c1aas 2 r1ee-e 15 August, 0615 W N M e .