CALIFORNIA INSTITUTE OF TECHNOLOGY

Pasadena, Cal i forni a

SEMI-ANNWAL STATUS REPORT

for

NATIONAL AERONAUTICS AND SPACE ADMINISTRATION

Grant NGR 05-002-160

for

1 April 1970 - 30 September 1970

https://ntrs.nasa.gov/search.jsp?R=19710005847 2020-07-03T07:11:10+00:00Z

TABLE OF CONTENTS

PAGE

Summaries

I . Cosmic Rays (Vogt, Stones Fanselow) 1

11. Cosmic Rays (Neher, George) 5

I I I -, Interpl anetary Magnetic Fie1 d and P1 asmas (Davis, Jokip i i , Hollweg, Scholer)

5

Further Description o f Activit ies

I . Cosmic Rays (Vogt, Stone, Fanselow) 7

11. Cosmic Rays (Neher, George) 21

1111. Interplanetary Magnetic Field and Plasmas 21 (Davis , Jokipi i , Hol lweg , Schol e r )

Expenditures 24

B i b l i ography 25

SEMI-ANNUAL STATUS REPORT

NASA Grant NGR 05-002-160

Cal i forni a Insti tu te of Techno1 ogy

1 April 1970 - 30 September 1970

The present report covers the research ac t iv i t i e s i n cosmic rays and interplanetary magnetic f ie lds and plasmas which f o r the past seven years had been supported mainly w i t h funds from NASA Grant NGL 05-002-007. Dur ing the period 1 October 1969 - 31 March 1970, the above a c t i v i t i e s were supported par t ia l ly w i t h remaining funds from NASA Grant NGL 05-002-007 and w i t h new funds from NASA Grant N G R 05- 002-160. Henceforth the ac t iv i t i e s i n cosmic rays and interplanetary f ie lds and plasmas w i 11 be supported completely under NASA Grant NGR 05-002- 160.

The report i s divided i n t o sections which describe the various separate b u t in terrelated a c t i v i t i e s , followed by a summary of s t a f f , expenditures and a b i bl i ography.

For the benefit o f the reader w h o may not be interested i n tech- nical detai l the report opens w i t h a brief summary of the various ac t iv i t i e s .

SUMMARY

I . Cosmic Rays (Vogt, Stone, and Fanselow)

T h i s group's research program i s directed toward the investigation of the astrophysical aspects of cosmic radiation and the radiation en- vironment of the earth by means of par t i cle-detector systems flown on spacecraft and balloons. The main e f fo r t s of the group have been directed toward the following three categories o f experiments.

A , Experiments on NASA Spacecraft

1. A s a t e l l i t e experiment launched on 060-4 on 28 July 1967. T h i s experiment, which is be ing carried out jo in t ly by E , C. Stone a t Caltech, J . A . Simpson a t the University of Chicago, and C . Y . Fan a t the University of Arizonas i s measuring the time-dependent energy spectra of protons (1 .2 t o 40 MeV) (0.4 t o 'L 1 MeV). be presented a t the Fall Meeting of the American Geophysical Union. J . W . Brown, a graduate student, has investigated the l a t i tude and local time dependence of electron precipitation "spikes", f i n d i n g one population to be associated w i t h ener- ge t ic par t ic les i n the magnetosheath and a second population to be due to pitch angle scat ter ing of trapped radiation. L. C . Evans, a doctoral candidate, has ident i f ied the rapid access of so la r electrons i n t o the polar region and i s combining these resu l t s w i t h those fo r protons i n constructing a model fo r the access of energetic solar par t ic les i n to the magnetosphere. Dr. J . L. Fanselow has studied magnetospheric r ig id i ty cutoff e f fec ts and has determined tha t the anomalously low cutoff la t i tudes cannot be at t r ibuted to d i f f u s i o n inward from the cal cul ated access region a

alpha par t ic les ( 4 t o 160 MeV), and electrons Results of three different studies will

2 , A s a t e l l i t e experiment launched on 060-6 on 5 June 1969. T h i s experiment is measuring the d i f fe ren t i a1 energy spectra of protons and alpha par t ic les between 700 keV and 1 GeV/nucleon and of electrons between 1 MeV and 500 MeV. The different ia l measurements can be extended t o 15 GV by u s i n g the geomagnetic f i e ld . the solar modulation of galact ic cosmic rays, the acceleration and interplanetary propagation of so la r cosmic rays, and the penetration o f charged par t ic les into the magnetosphere. from S. S. Murray's doctoral disser ta t ion on the propagation of so la r f l a r e protons will be presented a t the Fall Meeting of the American Geophysical Union. These resul ts indicate tha t fo r low energy protons (< 10 MeV) the e f fec ts of convection and adiabatic deceleration rather than diffusion dominate the decay phase of

T h i s broad energy range will permit detailed studies of

Results

- 3-

the 7 June 1969 f l a r e event. A second doctoral student, J . E . Lup ton , i s extending the

A s a t e l l i t e experiment t o be f This experiment i s designed t o spectrum of electrons (0.18 t o energy spectra of the nuclear

3.

propagation studies I

own on IMP-H and -J i n 1971 and 1972. measure the di f ferent i a1 energy 2.8 MeV) and the different ia l sotopes of hydrogen he1 i um,

lithium, and beryllium (0.5 t o Q 50 MeV/nucleon). This experi- ment will allow studies of so la r and galact ic cosmic rays and of magnetospheric acceleration of charged par t ic les and the inter- relation of those par t ic les to the par t ic les trapped in and precipitated from the magnetosphere. This group has continued t o assume responsibil i ty for the sol id s t a t e detector, s c i n t i l l - a to r , and photomul ti pl i e r t e s t and eval ua t i on programs and for the software aspects of the ground support equipment (GSE). add i t ion , th i s group has recently assumed the responsi b i 1 i t y for the completion of the GSE hardware. in January, 1970, the subcontractor was forced t o interrupt fabrication for 3 months a t the end o f FY 70. Fabrication has since resumed and electronic modules are being combined into sub-assemblies.

I n

Due t o a funding reduction

4. A s a t e l l i t e experiment t o be flown on HE This experiment has been proposed jo in t ly by this group and M. H. Israel and J . Klarmann (Washington University), W . R . Binns (McDonnel l-Douglas Research Laboratories) ?I and C. J.. Waddington (University of Minnesota) and i s designed t o measure the chemical abundances o f r e l a t i v i s t i c high-Z cosmic ray nuclei (17 - Z - 130). The results of such measurements are of significance t o the studies of nucleosynthesis and s t e l l a r s t ructure , the existence of extreme transuranic nuclei the origin of cosmic rays, and the physical properties o the i n t e r s t e l l a r medium. This group 's e f for t s have been directe toward experiment design and proposal preparation i n i t i a l l y as an independent group and then as a member of the collaboration which was formed a t NASA's request,

< <

1

, , -4-

B. Experiments Performed under the NASA Balloon Program.

These experiments generally are e i the r prototypes of experiments on existing or future NASA spacecraft, o r they complement such observations

1. A bal loon-borne proton-a1 pha-electron (pae) spectrometer w h i c h i s essent ia l ly identical t o the above described OGO-6 s a t e l l i t e detector system. support, only one f l i g h t w i t h the pae gondola could be schedul- ed for the 1970 Skyhook program a t F t . Churchill e (see Table I ) was timed t o occur simultaneously w i t h polar passes of the equivalent detector system aboard OGO-6, and b o t h instruments performed successfully. calibrations o f the pae and 060-6 detector systems on par t ic le accelerators was completed w i t h runs on the Berkeley 184" cyclotron (see par t C ) . A study of the long term so lar modu- lation effects on protons and alpha par t ic les , based upon pae data collected over the 1966-1970 interval I) has been in i t i a t ed . Also under investigation are the proton and a1 pha observations performed simultaneously w i t h the pae and 060-6 detector systems i n 1969-1970. This work will form part of the doctoral dis- ser ta t ion of T . L . Garrard.

Due t o curtailments i n balloon

The f l i g h t

A ser ies of extensive

2. A balloon-borne magnetic spectrometer (e+) f o r the investigation of the energy spectra o f negatrons and positrons i n the 12 t o 800 MeV/c momentum range. w h i c h formerly covered the 10 t o 200 MeV region was extended t o about 800 MeV by the incorporation of a larger bending magnet and a gas Cerenkov counter. The modified spectrometer was flown four times from FL. Churcki 11 Manitoba, d u r i n g the 1970 Skyhook program for studies o f the primary cosmic-ray electron spectrum, Analysis of the 1968 and 1969 e& data has been continued.

The energy range of the instrument,

J

A paper on magnetospheric phenomena ("Diurnal Geomagnetic Cutoff Variations for Positrons and Negatrons near A=68') based upon the e+ balloon observations, was presented a t the S p r i n g Meeting o f t h Ameri can Geophysi cal Union e

-5-

A paper on the propagation of cosmic-ray produced electrons and photons i n the atmosphere and the analysis of electron measurements made i n the atmosphere has been submitted for pub1 i cation ( K . P . Beuermann: Photons i n the Upper Atmosphere").

"Secondary Electrons and

Investigations and tes t ing of pressure recording devices fo r h i g h a l t i t ude balloon f l i gh t s were continued.

C . Experiments on Part ic le Accelerators e

The accelerator version of the pae and OGO-6 range telescope (see Status Report NGL 05-002-007 of 1 Apr i l t o 30 September 1969) has been calibrated w i t h the a-par t ic le beam of the 184" cyclotron of the Lawrence Radi a t i on Laboratory. These resul ts w i t h the proton beam of the synchrocyclotron of NASA's Space Radiation Effects Laboratory, are used w i t h a Monte Carlo type computer cal- culation to correct the pae and OGO-6 data f o r the e f fec ts of nuclear interactions i n the detector system.

and those obtai ned

11. Cosmic Rays (Neher, George)

of the so l a r plateau have been essent ia l ly completed u s i n g the ioniza- t ion chamber data from 060-2. The physical interpretation of the differences between these and previous resul ts i s presently under stud,y. In addition, ion chamber observations of electron precipitation spikes

by Brown and Stone on the same s a t e l l i t e .

Studies of the behavior of quasi-trapped par t ic les a t the edges

were correlated w i t h the charged-parti c le telescope observations

111. Interplanetary Magnetic Field and Plasmas (Davis, Jokipii Hollweg, Scko 1 e r ) Much of the work d u r i n g the l a s t six months was related t o the

nature and source of the observed fluctuations in magnetic and plasma parameters and to the e f fec ts of inhomogeneities on the wopagation of cosmic rays and radio waves i n interplanetary space.

-6-

1. The analysis by J . W. Belcher, a graduate student, and L, Davis of the outwardly propagat ing Alfv6n waves has been organized on the basis of the so la r wind velocity s t ructure . The waves are quite strong and quite pure i n the h i g h velocity parts of the streams including the f i rs t ha1 f of the return to low velocity. propagated outward from the lower corona and that they are derived from the waves t h a t heat the corona. T h e waves are strongest, b u t not so purely Alfv&ic, near the parts of the so la r wind streams where the velocity increases rapidly and the h i g h velocity stream is interact ing w i t h preceding lower velocity plasma. The h i g h amplitudes and mixed modes may be due partly to local generation of Alfvgn and magnetoacoustic waves i n this interaction region and partly t o amplification and conversion of the Alfvgn waves of coronal origin i n a region of compression and bending of the f i e l d l ines .

I t seems probable t h a t these waves have

2 . Theoretical work on the propagation of cosmic rays i n the so la r wind was continued by Jokipii . on the modern s t a t i s t i c a l theory of cosmic-ray transport i n the solar wind has been completed f o r Reviews of Geophysics and Space Physics. usually applied a t the s u n i n the theory is obviously not correct;

The e a r l i e r work by Jokip i i , pa r t i a l ly i n collaboration w i t h Hollweg, on the sc in t i l l a t i on of radio sources produced by inhomogeneities i n the so l a r wind was continued and a s tar t made on extending i t t o pulsar s c in t i l l a t i ons produced by density fluctuations i n the i n t e r s t e l l a r medium.

A lengthy review paper

I t was found that the boundary condition

fur ther study of this problem i s i n progress.

3.

4. Dr, M. Scholer, who had worked i n the group fo r a year on a NASA post-doctoral fellowship, returned to Munich early i n September, and Dr. J . V. Hollweg joined the group i n August. Dr. Scholer, i n collaboration with J . W . Belcher, completed a study of the influence of Alfv6n waves on f a s t magnetohydro- dynamic shock waves. Dr. J . V. Hollweg is investigating theoret- ical aspects of Alfvgn waves i n the so la r medjumg including the i r generation by the supergranul a r motions i n the photosphere the i r possible contribution t o so la r wind heating, and the properties of 1 arge amp1 i tude A1 f v 6 n waves

- 7-

FURTHER DESCRIPTION OF ACTIVITIES

I. Cosmic Rays (Vogt, Stoneg Fanselow)

The e+ Magnetic Spectrometer

The ac t iv i t i e s on this project were concentrated upon the prepara- t i o n and execution of balloon observations and the analysis of data from balloon f l i gh t s i n 1968 and 1969.

been described l’n Status Report NGL 05-002-007 for 1 Apri l 1968 t o 30 September 1968 and i n the doctoral dissertation o f C . J . Rice (“Primary Cosmic-Ray Positrons and Negatrons i n 1968 a t Energies between 11 and 204 MeV”). For the 1970 observations, the different ia l energy range of the e+ spectrometer was extended t o about 800 MeV by the incorporation of a larger bending magnet (2.3 kG) and a gas Cerenkov counter (See Status Report NGL 05-002-007 for 1 April t o 30 September 1969 and NGR 05-002- 160 for 1 October 1969 t o 31 March 1970).

The e+ magnetic spectrometer used i n the 1968 and 1969 studies has

4

A ser ies of four ba l loon f l i gh t s w i t h the e+ spectrometer was made from Fort Churchill, Manitoba, under the 1970 Skyhook program. A f l i g h t log i s presented i n Table I . equipped w i t h contractor supplied valves t o allow f loa t levels a t several atmospheric depths. valves f a i l ed t o close upon command, causing uncontrolled descent w i t h an emergency termination of the f l i gh t . No spare balloons were available i n the 1970 programs and the re f l igh t had t o be performed w i t h a much less

3 desirable unvalved 10.6 million f t bal loon. The instrument modifications of the e+ spectrometer performed well, and the data analysis has begun.

A paper on magnetospheri c phenomena ( “Diurnal Geomagneti c Cutoff Variations for Positrons and Negatrons Near A=68°”), was presented a t the 1970 Spr ing Meeting of the American Geophysical Union. The non-dipole character o f the geomagnetic f i e l d , e,g. , the presence of closed f i e ld l ines a t lower la t i tudes and essent ia l ly open f i e l d l ines (geomagnetic t a i l ) a t h i g h e r la t i tudes, i s reflected in the geomagnetic cutoff values for cosmi 6 rays. Because of their low charge-to-mass ra t io electrons are particularly suited as probes of the geomagnetic cutoffs down t o very low r ig id i t i e s . rl’gidi t i e s near Fort Churchill I) ranging from about 100 MV a t day t o below 12 MV a t n i g h t .

F l i g h t 70C3M used a 10.6 million f t3 balloon

The f l f g h t d i d not reach i t s objectives since the

Electron data have revealed a diurnal variation o f the cutoff

Trajectory calculations for low r ig id i ty par t ic les i n a

- 8-

non-dipole model magnetosphere have been made by Smart, Shea and Gall a

The resul t i ng cal cul ated cutoff ri g i d i ti es versus 1 oca1 t i me are shown i n Figure 1, their contours are labeled w i t h geographic la t i tude X and invariant la t i tude A for the 100' West meridian. The data poin ts resul t ing from this group's e& observations give the t ransi t ion times from the day to n i g h t - t i m e geomagnetic conditions a t specif ic r i g i d - i t i e s - The observed negatron and positron t ransi t ion times are plotted separately, w i t h local time mirrored through noon i n accordance w i t h the charge symmetry of the model calculations. All e+ t ransi t ions occurred w i t h i n 1/Z0 of A=68' Fa and w i t h i n 4' of the 100' W meridian appropriate t o the calculations. One f inds t h a t the general level of the measured cutoffs versus local time agrees reasonably well w i t h some of the calculated curvesS g i v i n g qual i ta t ive support to this model of diurnal variations e

calculated for invariant la t i tudes of 70' t o 74O, i .e. 2' t o 6' higher than the invariant la t i tude of the observations. posi tron-negatron asymmetry does not appear. indicate tha t the model magnetosphere used by Smart, Shea and Gall does not ye t adequately describe actual conditions

re la t ively small f lux of primary cosmic-ray electrons i n the 10 MeV to several hundred MeV energy range is d i f f i c u l t t o separate from the often equal ly abundant atmospheri c secondary electrons. has devoted considerable e f f o r t to improvements of this analysis. The intensi ty of electrons is determined over a wide range o f atmospheric depths and then analyzed w i t h the he lp of detailed calculations on the secondary negatron and positron growth curves i n the atmosphere. A description of the cal cul a t ions has been submi teed fo r pub1 i cat i on ( K . P. Beuermann: "Secondary El ectrons and Photons i n the Upper Atmosphere e ' I )

and 3, for example, show the in tens i t ies o f negatrons and positrons respect- ively as a funct ion of atmospheric depth. atmospheric secondary fluxes measured near Fort Churchill i n 1968, the phantom points indicate, for comparison total f l uxes (atmospheric secondaries plus cosmic-ray primaries) a t f l o a t a l t i tude . show the atmospheri c secondary i ntensi t i e s cal cul ated by Beuermann on the basis of production spectra used by Perola and Scarsi. T

However, the data seem t o agree best w i t h cutoff conditions

Also, the predicted These discrepancies may

In the analysis of measurements taken on balloon f l i gh t s the

This group therefore

F i gures 2

The sol id data points represent

The sol id l ines

dashed l ines

-9-

give the best f i t , us ing the calculated functional depth dependence and adjusting the absolute in tens i t ies used by Perola and Scarsi . The calculations show tha t the functional depth dependence of the electron intensi ty deviates considerably from the commonly assumed l inear growth. Figure 4 gives the exponent n i of a power law f i t f ( x ) a x n i to the growth curves of the atmospheric secondary f l u x as function of energy. sol id curves give n fo r a f i t t o the 2 t o 15 9/cm depth interval , the dashed curves give n f o r the 15 t o 40 g/cm interval . The functional depth dependence varies only i nsi gni f i cantly w i t h sol a r cycle changes hence the resul t s shoul d be generally appl i cab1 e .

i s d i rec t ly related to the accuracy of the a l t i t ude determination. T h i s group investigated the useful ness of the "Metrophysi cs" thermal conduction type pressure transducers, which are frequently used i n Skyhook f l i gh t s , by flying such an instrument simultaneously w i t h "Wallace-Tiernan" aneroid type reference gauges. One must conclude tha t the thermal conduction type devices are unsuitable f o r precise a1 ti tude determination on vented balloons. a Metrophysics Pressure Transducer, It SRL Internal Report #20). 5 i 11 ustrates the response of a Metroghysi cs transducer t o d i f fe ren t he1 i um- a i r mixtures, i . e . output voltage versus pressure. Figure 6 gives a typical example o f the a l t i tude prof i le of a balloon f l i g h t as seen by a Metro- physics transducer and the Wall ace-Tiernan reference. The numbers attached t o the Metrophysics data indicate roughly the percentage of helium con- tamination which would explain the deviation from the Wallace-Tiernan reference. Rough estimates, u s i n g a one-dimensional diffusion equation, indicate the poss ib i l i t i es of the quoted helium contaminations near the vented ball oon e

capaci ti ve type pressure transducer. This device shows promise for ball oon f l i gh t s as i t is insensitive t o the composition of the atmosphere and has very h i g h overall accuracy (< 1%). The agreement w i t h a Wallace-Tiernan reference aneroid was typically be t te r than 0.2 g/cm . Howevers repeated calibrations have shown t h a t zero shifts as large as 0.2 g/cm can a r i se d u r i n g a period o f a month i f the device i s l e f t a t atmospheric pressure. Generally, much smaller s h i f t s are noted f f the calibrations are repeated often e

The 2

2

The accuracy of the atmospheri c secondary corrections obviously

( C . Todd: "The Effect of a Helium Contaminated Atmosphere on F i g u r e

During the 1970 Skyhook program, this group used a "Rosemount"

2 2

- 10-

Experiments on Part ic le Accelerators

T h i s group 's OGO-6 and pae detector systems use a range versus energy-loss technique for the measurement of the different ia l energy spectra of protons and helium below about 300 MeV/nucleon. undergoes a nuclear interaction i n the material of the range telescope, i t s unique dE/dx versus range relat ionship may be suf f ic ien t ly a l tered t o cause errors i n the determination o f i t s charge and energy. correct the data f o r the ef fec ts of nuclear interactions a special computer program (FLINT) has been developed. FLINT uses Monte Carlo techniques to calculate the probability of a proton o r alpha par t ic le of a given energy hav ing a certain range i n the telescope stack. action processes a re needed as i n p u t parameters f o r FLINT. Their values, i n the i n i ti a1 cal cul a t i ons , are based on nuclear emu1 s i on resul ts from cosmi c- ray data, on accelerator measurements, and on Monte Carlo calculations. The program is affected by two major errors . First, the available emulsion data general ly have poor s t a t i s t i cs and the possi b i 1 i ty of systematic errors . Secondly, no resul ts are available on correlations between secondary par t ic les from an interact ion; the measurement of s t a t i s t i c a l l y s ignif icant cor- relations i n interactions producing on the order of 10 secondaries would require forbiddingly 1 arge amounts of accel e ra tor time. the i n i t i a l FLINT resul ts are being compared w i t h resul ts from a d i rec t accelerator calibration of a special " fas t" version of the OGO-6 pae instru- m e n t . (See Status Report NGL 05-002-007, 1 April - 30 September 1969). The accelerator data are being used t o adjust the i n p u t parameters of FLINT for optimal agreement. Calibrations were performed a t the 600 MeV synchro- cyclotron of NASA's Space Radiation Effects Laboratory (Langley) with protons a t energies ranging from 115 MeV to 570 MeV. Alpha-particle calibrations a t 187 MeV/nucleon and 213 MeV/nucleon were performed a t the 184" cyclotron of the Lawrence Radiation Laboratory (Berkeley). An example of i n i ti a1 (pre- sal ibrat ion) FLINT resul ts and the corresponding acceleration derived data points is shown i n Figures 7 and 8. Given are the percentages of protons (or a-particles) as function of energy which s top i n a certain tel interval (34 t o 66 g/cm W equivalent) without tri gqeri ng the anti coi nci dence shield. The s t a t i s t i c a l uncertainit ies of the FLINT calculations are rough- ly comparable t o those of the measured calibration points. f i t adjustment has been made, the FLINT resu l t s will be combined with enerqy-

I f a par t ic le

In order t o

Cross-sections f o r nuclear inter-

For these reasons

2

After a best-

-11-

loss sal cul ations (based upon theory and d i rec t accelerator cal i brati ons ) t o create a response function for the 060-6 and pae range telescopes. telescope response function will be used t o accurately derive cosmic-ray spectra from the range-telescope data.

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-21-

11. Cosmic Rays (Neher, George)

From April 31970, through September, 1970, work has continued on the study of quasi-trapped par t ic les using the 060-2 and 060-4 ion chamber data in the la t i tude range 68 < A < 80'. Data analysis has now been completed. The iso-intensity contours of the quasi- t rapped par t ic les have been found t o depend on local time, invariant la t i tude , and the geomagnetic act ivi ty index K suf f ic ien t resolution i n the da ta fo r the determination of any possible e f fec t of a l t i tude , longitude, or t i l t -angle of the ear th ' s magnetic dipole axis. from the I n j u n 2 , Alouette 1 and Alouette 2 studies. There i s basic agreement with the previous work, b u t small differences do ex i s t . The physical interpretation of these differences i s presently under study.

In addition, 060-4 ion-chamber da ta have been prepared for correleation w i t h the observations of high-lati tude electron "spikes" by J . W . Brown and E . C. Stone. The object o f t h i s work i s t o correlate the da ta from the 060-4 par t ic le telescopc with ion-chamber d a t a from the same time periods. I t i s hoped t h a t more accurate values of the spectral index and angular distribution o f these fluxes will resu l t .

There i s not P '

The resul ts o f th i s study have been compared with those

I 11. Interplanetary Magnet1 c Fields and P1 asmas (Davis Joki p i i and Scholer)

Hol lweg ,

I. The analysis of the Mariner 5 magnetometer and plasma d a t a has progressed t o the point where an extensive paper has been completed by J . W . Belcher and L. Davis and a substantial block of reduced data is nearly ready for submission t o the Data Center. character o f the waves have been strengthened, and the estimate o f t he i r fractional contribution t o the fluctuations has been

In this paper, the e a r l i e r arquments for the Alfv&ic

-22-

2.

somewhat increased. The ana lys is i s organized on t h e bas is o f a model o f the s o l a r wind v e l o c i t y s t ruc tu re . the A l fvgn waves i n the i n t e r p l a n e t a r y medium seem l i k e l y t o be t h e undamped remnants o f waves generated a t o r near the sun. The h igh l e v e l o f wave a c t i v i t y i n h i g h v e l o c i t y , h i g h temper- a tu re streams can be i n t e r p r e t e d as evidence f o r t h e extens ive hea t ing o f these streams by wave damping near the sun.. The h ighes t l e v e l o f A l f v g n i c ac t i v i t y ,wh ich i s found i n the com- press ion reg ions a t the l ead ing edges o f h igh v e l o c i t y streams, may be due e i t h e r t o t h e a m p l i f i c a t i o n o f ambient A l f v6n waves i n h igh v e l o c i t y streams as they are swept i n t o t h e compression regions o r t o the f resh generat ion o f waves i n these regions by the s tream-s tream i n t e r a c t i ons . The observed very 1 ow 1 eve1 o f the magnetoacousti c modes i s evidence f o r t h e i r s t rong dampi ng. The !B~!R an isot ropy i s viewed as due t o t h e p a r t i a l conversion o f t he A l f v6n waves i n t o the damped magnetoacoustic modes as they are convected away from t h e sun; t h i s process c o n t i n u a l l y t rans- f e r s energy from the microscale f i e l d f l u c t u a t i o n s t o the thermal- i z e d s o l a r wind plasma.

Most o f

J o k i p i i has completed an extens ive review o f t he modern, s t a t i s t i - ca l theory o f t he t ranspor t o f cosmic rays i n the s o l a r wind f o r Reviews o f Geophysics and Space Physics. discussed on ly as they i l l u s t r a t e the phenomena under d iscuss ion. A b r i e f i n t r o d u c t o r y sec t i on surveys the h i s t o r i c a l development o f t h e theory. The dominant e f f e c t on the motion o f cosmic rays i n t h e s o l a r wind i s t he i n t e r p l a n e t a r y magnetic f i e l d , which i s i r r e g u l a r and which 3s t he re fo re bes t t rea ted s t a t i s t i c a l l y , us ing random functions. The magnetic i r r e g u l a r i t i e s s c a t t e r t h e cosmic rays i n p i t c h angle, so t h a t t o a good approximation the cosmic rays d i f f u s e through the i r r e g u l a r magnetic f i e l d . Using a s t a t i s t i c a l ana lys is o f t he equations of motion, one may r e l a t e the d i f f u s i o n tensor t o t h e power spectrum o f t he magnetic f i e l d , whi ch i s i n p r i n c i p l e measurable. The resu l ti ng general t ranspor t theory r e l a t e s t h e motion o f cosmic rays, s t a t i s t i c a l l y , t o the s o l a r wind v e l o c i t y and magnetic f i e l d .

Observations are

- 23-

Application of the theory both t o the modulation of galact ic cosmic rays by the so la r wind and to the propagation of so la r cosmic rays i s discussed i n detai l I t i s concluded the present theory explains the principal phenomena q u i te we1 1 e

Future theoretical work will probably be devoted t o o b t a i n i n g better solutions of the equations t o obtaining be t te r val of the parameters, and t o t reat ing higher order o r more subtle e f fec ts .

3. M. Scholer and J . W. Belcher extended the usual Rankine-Hugonoit equations f o r f a s t shocks to include the momentum and energy f l u x i n Al fv6n waves. The resulting equations were solved numerically f o r a wide range of parameters. The presence of waves lowers the post-shock density and temperature. For values of the pre-shock f a s t Mach number smaller than a c r i t i ca l valueg the post-shock fast Mach number i s greater t h a n 1, result ing in a so-called non-evolutionary shock. M. Scholer a lso studied the broadening and dis tor t ion of a r t i f i c i a l ion clouds i n an ionized background w i t h a homogeneous magnetic fie1 d.

Jokipii served on the Space Astronow Panel of the Astronomy Survey Committee of the National Academy of Sciences. attended the Solar Terrestr ia l Physics Symposi um i n Leningrad i n May, 1970, and served as Secretary of Commission 43 of the International Astronomical Union a t i t s General Assembly i n Brighton, England. Davis served on the National Academy o f Sciences, June, 1970, Summer Study on the exploration of Venus and on the Magnetometer Instrument Team fo r the 1973 Mercury- Venus Design Study. en t i t l ed "The Configuration of the Interplanetary Magnetic Fl"eld" a t the Solar Terrestrial Physics Symposium i n Leningrad i n May, 1970. He served as President of Commission 43 a t the General Assembly of the International Astronomical Union i n Bri ghton Engl and i n August, 1970.

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BIBLIOGRAPHY

1968

Althouse, W. E . , E. C. Stone, R. E. Vogt and T. H. Harrington, "A Solar and Galactic Cosmic Ray Sa te l l i t e Experiment1Is IEEE Transactions on Nuclear Science, NS-15, No. 1, 229 (1968).

Beuermann, K. P., C. J . Rice, E. C. Stones and R e E. Vogt, "Cosmic-Ray Electrons and Positrons Between 6 and 200 MeV", Bull. Am. Phys. S O C . ~ Sere 11, - 13, 11, 1411 (1968).

Daviss L . , E . 3. Smith, and J , Belcher, "The In-Flight Determination of Spacecraft Magnetic Fiel d Zeros" Trans. Am. Geophys a Union - 49, 257 (1968).

Griffel , D. H . , "The Kinetic Theory of the Solar Wind and i t s Inter- action w i t h the Moon", Thesis, California Ins t i tu te o f Technology (1968).

I s r ae l s M. H . , "Primary Cosmic Ray Electrons and Albedo Electrons a t Energies between 12 and 1000 MeV", Thosis, California Ins t i t u t e of Technology (1968) e

I s r ae l s M. H . and R. E. Vogt, "Diurnal Intensity Variations of Cosmic Ray Electrons Observed a t Balloon A1 t i tudes near Fort Churchi 11 Manitoba", Trans. Am. Geophys. Union - 49, 240 (1968).

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Sisco, G , L., L . Daviss, J r . , P. J . Coleman, J r , , E. J . Smi th and D , E. Jones Magnetic Fiel d: Mariner IV" J . Geophys e Res - 73, 61 ( 1968).

"Power Spectra and Discontinui t i e s o f the Interp? anetary

-26-

Smi th , E . J . , L . Davis, J r . , D. E. Jones9 P. J . Coleman, J r . , "Magnetfc Measurements i n the Earth's Magnetosphere and Magnetosheath: Mariner VI' Trans e Amer. Geophys e Union - 49, 278 (1968).

Snyder, C. W . , E. J . Smith, L. Davis, J r . , A. J . Lazarusg P. 3, Coleman, J r . , and D. E . Jones, "The Interaction o f Venus w i t h the Solar Wind", Trans. Amer. Geophys . Union - 49. 224 (1968) e

Stone, E. C . , R. E. Vogt and K. P. Wenzel, Wessungen der Albedo- Protonen der Kosmi schen Strahl ung" ., Verhandl ungen der Deutschen Physikalischen Gesellschaft, - 6 (1968) e

Wenzel, K. P . "Primaere, Sekundaere, und Albedo-Protonen aus der Kosmischen Strahl ungll Thesis Ruprecht-Karl -Uni versi t a e t He1 del berg (1968).

-27-

1969

Belcher, J . W . , L. Daviss J r . , and E. J . Smith, "Large Amplitude Alfven Waves i n the Interplanetary Medium: Mariner 5", J . Geophys. Res. - 74, 2302 (1969).

BeuermannS K . P . , C. J . Rice, E , C. Stone, and R . E . Vogt, "Cosmic- Ray Negatron and Positron Spectra between 12 and 220 MeV," Phys. Rev. Letters 22, 492 (1969).

Beuermann K. P . , "Elektronen und Photonen der Sekundaeren Kosmischen Strahlung i n der Oberen Atmosphaere", Vortr. Ex 47, Argei tsgemeinschaft "Extraterrestrische Physi k " Berlin, March 1969

Dolginov, Sh. Sh, E . G. Eroshenko, and L. Davis, "On The Nature of the Magneti c F i e l d near Venus 'I Kosmi ches kiye I s s l edovaniya 747 ( 1969) a

Evans, L. E. and E . C. Stone, "Access of Solar Protons i n t o the Polar Cap: 5127 (1969).

A Persistent North-South Asymmetry", J . Geophys. Res. - 74,

Griffel , D. H., and L. Davis, J r . , "The Anisotropy o f the Solar Wind", Plan. Spac Sci. - 17, 1009 (9969).

George, Michael James "Mew Measurements on the Absol Ute Cosmic Ray Ionization from Sea Level t o 1540 Kilometers Altitude, Thesis, California Ins t i t u t e of Technology, (1969).

I s r ae l s M e H . , "Cosmic-Ray Electrons Between 12 MeV and 1 GeV i n 1967," J . Geophys. Res. 74, 4701 (1969).

I s rae l , M, H . , and R. E. Vogt, "Characteristics o f the Diurnally Varying Electron Flux near the Polar Cap!, J . Geophys. Res. - 7 4714 (1969).

Jokipi i , J . R. and L . Davis, J r . , "Long Ma elength Turbulence and the Heating of the Sol a r Wind" Ap. J . - 156, 1101 (1969) e

-28-

Joness D. E . , E . J . Smi th , L. Davis, J r . , and P. J . Colemans "Search Marfner 4", for a Lunar Wake a t Large Distances from the Moon:

J . Geophys. Res. - 74, 3037 (1969)

Rice, C. J . , "Primary Cosmic-Ray Positrons and Negatrons i n 1968 a t Energies between 11 and 204 MeV", Thesis, California Ins t i tu te o f Techno1 ogy (1969)

Stone, E . C. and L. Evans9 "A Persistent North-South Asymmetry d u r i n g a Polar Cap Proton Event:, Trans. Am. Geophys. U n i o n s - 40, 306 (1969).

Stone, E . C. and L. Evans, "Diffusion of Solar Cosmic Rays in to the Magnetotail", XI. Int . Conference on Cosmic Rays, Budapest, Hungary (1969).

.

1970

Belcher, J . W . and L. Davis, "Anisotropy i n the Microscale Fluctuations of the Interplanetary Magnetic Field", Trans Am, Geophys. U n i o n s - 51, 413 (1970)

Beuermanns K. P. "Secondary Electrons and Photons i n the Upper Atmosphere'', (submitted for publication).

Beuermann, K. P . , C. J . Rice, E. C. Stone, and R. E. Vogt, "Cosmic-Ray Negatron and Positron Spectra Observed near Fort Churchill i n 1968", Acta Physica Academiae Scientiarum Wungaricae - 29, Suppl . 1, 173 (1970).

Brown, J . W . and E. C. Stones "High Energy Electron Spi kes", Trans Am. Geophys. U n i o n , - 51, 807 (1970).

Davis, L. J r . , "The Configuration of the Interplanetary Field", Proc. Leningrad Symposium on Solar-Terrestrial Physics ( i n press)

Davis, L. and M. Goldstein, "Magnetic-Dipole Alighment i n P u l s a r ~ " ~ Ap. J . Letters - 159, L81-85 (1970).

Evans, L . C . and E. C. Stoneg "Access of Solar Flare Protons and the Config- urati on of the Magnetospheri c Tai 1 'I Trans. Am. Geophys e Union - 51 800 (9970) e

Fanselows J . L., "Cosmic-Ray Cutoffs from 1-40 MeV", Trans. Am. Geophys. Union, - 51, 800 (1970).

George, M. J . , "New Data on the Absolute Cosmic-Ray Ionization i n the Lower Atmosphere", J . Geophys. Res - 75 3693 (1970)

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e "Observations of the Cosmic-Ray Knee w i t h a Polar O r b i t i n g Ioni za t i on Chamber" J Geophys Res a - 75 3159 ( 1970)

Greenstadt E. W . , L. Davis and E. J e Smith "Possible Dependence o f Venus and Mars Bow Shock Characteri sti cs on Interpl anetary Field Orientation" Trans * Am. Geophys Union - 51, 408 (1970)

Jokipii J . R. , "The Transport of Cosmic Rays i n Space'' Bull. Am. Phys. SOC. - 15, 589 (1970).

Jokipii J . R . "On the Thin-Screen Model o f Interplanetary Sc in t i l l a t ions" , Ap. J . - 161 , 1147 (1970)

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lYurrayI S. S . , E . C . Stone, and R . E. Vogt, "Non-Diffusive Effects i n the Propagation o f 1-10 MeV Solar Protons'IS Trans. Am. Geophys. Union, - 51, 798 (1970).

Rice, C. J . K. P. Beuermanns E . C . Stone, and R . E . Vogt, "Diurnal Geomagnetic Cutoff Variations For Positrons and Negatrons near A = 68°1, Trans. Am. Geophys. Union, - 51, 230 (1970).

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