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“SEMIANNUAL PROGRESS REPORT 


Grant NAG8-058 


/OH J /V2 — ' 

H f 


INVESTIGATION OF LOW ENERGY SPACE PLASMA 


April 


September, 1987 


by 

Richard H. Comfort 
and 

James L. Horwitz 


Prepared for 

National Aeronautics and Space Administration 
George C. Marshall Space Flight Center 
Marshall Space Flight Center, Alabama 35812 


Submitted by 


The University of Alabama in Huntsville 
College of Science 
Huntsville, Alabama 35899 


October, 1987 


(NASA-CR- 1 81 3 80) INVESTIGATION OF LOi N67-30I89 

ENERGY SPACE PLASMA Semiannual Proqress 
Report, Apr. - Sep. 1987 (Alabama Univ. ) 

14 p Avail: NT IS HC A02/MF A01 CSCL 201 Unclas 

G3/75 0102712 


ANALYSIS TECHNIQUES AND SOFTWARE DEVELOPMENT 


An Important modification has been made in the method for 
computing ion densities from DEI/RIMS observations, based on the 
observed relationship between total plasma density and spacecraft ' 
potential. An iterative technique has been developed to require that 
this relationship be preserved in all individual observations, not 
just in the average sense observed. Results of employing this 
technique have been examined closely and are found to generally 
improve the final densities in terms of agreement with densities 
obtained from PWI upper hybrid frequency observations. It also has 
the effect of reducing scatter in the density vs. L profiles. By 
insuring that a common spacecraft potential is used in determining 
all ion densities, an improved accuracy and consistency in 
composition determinations also results. Since this technique has 
been developed as a separate stage in the processing, all previous 
results can be treated without reanalysis. A paper describing this 
technique is in preparation (Ref. 1). 

Techniques developed for automated analysis of data in the 
period after the RIMS radial head RPA malfunction have been 
incorporated into an interactive analysis program. This program is 
now functioning and is being used assess the accuracy of the 
automated procedure. It will also be used for case studies involving 
relatively small amounts of data in which accuracy is of paramount 
importance. Some optimization to reduce run time remains to be done. 



Accuracy o£ the end-head temperature analysis also remains to be 
examined . 

Improvements are continuing to be made in the temperature part 
of the automated analysis. The present algorithm for selecting 
points from the end head RPA curve was designed for the -Z head and 
works fairly well for that head. The +Z head has significantly 
different characteristics in the region of negative spacecraft 
potentials such that the algorithm does not operate well for that 
head under those conditions. The empirical model team is working to 
develop a single algorithm that will successfully select appropriate 
points from either head under all circumstances. 

Parameterization of a three-dimensional electric potential 
model, which includes parallel potential drops, has been largely 
completed, and the initial studies of ion motion in these fields 
begun. We have started quantitative modeling of the ion motions 
through the polar cap and then longitudinally into the nightside 
auroral arcs in order to investigate the possible origin of nightside 
auroral ion beams. 

A program has been developed to extract spin curve data from 
RIMS MAF1 files and integrate them with temperature, density and 
potential data from the analysis program for detailed statistical 
studies of the ion distribution in the DE-1 wake. Development of a 
second program to bin these results by appropriate dimensionless 
parameters for statistical analysis has been initiated. 


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A semi-kinetic model of the polar wind, originally written by 
Tom Moore, is being modified to correct discontinuities in the code 
results at the lower boundary. With a working code, we plan to study 
the effect of higher ion temperatures on the polar wind, particularly 
on the oxygen ion escape flux. 


DATA ANALYSIS AND MODELING 


A considerable volume of data has been processed during this 
period. Some of it has already been used in current studies, and 
some is for use in future statistical analyses. Temperature, density 
and potential files available for use have been extended to more than 
125 plasmasphere transits. For all of these files, the densities 
have been further processed by the technique noted above, which will 
be the standard henceforth. In addition, more than 75 of these data 
sets have been processed with the corresponding MAF1 files to provide 
inputs for a DE-1 wake analysis study, which is under way with Uri 
Samir . 

A preliminary study of ion composition was carried out to gain 
some idea of how it varied spatially and with geomagnetic activity. 

It was found that H+ constitutes from 70% to 85% of the plasma beyond 
L ~ 2, the smaller fraction tending to occur on the evening side. 

The He+ percentage of the total decreases with L, reaching a minimum 
and leveling off between L ” 2 to 3 at around 12% on the morning side 
and 18% on the evening side. The heavy ion 'torus' is evident in the 


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statistics for 0+ and 0 ++, Effects of geomagnetic activity were only 
weakly evident in this data set except in 0+, which shows an 

enhancement at lower L shells for the highest levels of activity. 
These preliminary results were presented to the IAGA Symposium on 
Variability of Ion Composition in the Earth’s Magnetosphere at the 
IUGG Meeting in Vancouver/ Canada (Ref. 2). 

Some additional work has been done in the study comparing 
theoretical models of ion distributions in spacecraft wakes/ in a 
tangential response to referee comments on the manuscript. The 
SHEATH program was used to examine the effect of aperture acceptance 
angle on the ratio of wake flux to ram flux. It is found that this 
ratio decreases with aperture acceptance angle due to the fact that 
flux variations with spin angle are greater in the wake than in the 
forward hemisphere (ram direction). This paper has now been accepted 
for publication (Ref. 3). 

Based on a subset of data from the earlier observational study 
of ion fluxes in the DE-1 wake (Ref. 4), we have carried out a 
preliminary theory/ observation comparison with the 1 -dimensional 
plasma expansion model of Singh. Over the range of ion Mach numbers 
typical of H+ in the plasmasphere, the agreement was reasonable, 
within factors of 3 to 5. However, a number of approximations had to 
be used in order to match the conditions of the calculation with 
those of the observations, with sufficient uncertainties involving 
both larger and smaller results that an adequate assessment of the 
plasma expansion mechanism could not be made. A more appropriate 
boundary geometry in a 2- or 3-dimensional model should provide a 


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much improved comparison. A draft of the preliminary results has 
been prepared for subsequent submittal (Ref. 5). Work on the 
improved model is continuing. 

Work is continuing on the study of polar 0+ beams. These beams, 
which have energies of ~ 10-20 eV, are being examined with 
observations from a number of DE-1 and DE-2 instruments, including 
RIMS, PWI, HAPI, EICS, SAI , and LAPI . 

RIMS data has been provided for use in a paper studying 
plasmapause signatures in F-region electron temperatures (Ref. 6). 

A review of our efforts to date on kinetic modeling of 
ionospheric ion transport into the magnetosphere will be presented to 
an IEEE simulation meeting in October, 1987 (Ref. 7). 


LABORATORY PLASMA FLOW STUDIES 


The capability to perform plasma-body interactions in a 
supersonic, collisionless, binary ion plasma stream has been 
successfully added to the space plasma physics research laboratory at 
SSL. The motivation for the new source was to develop a plasma beam 
where ions with unequal masses would flow at a common velocity, 
thereby simulating, for example, the motion of natural and/or 
artificial satellites through planetary ionospheres. The plasma beam 
characteristics are not optimal as yet, but sufficient to allow 


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performance of an experiment where the flow about the edge of a large 
plate was examined. The nominal conditions of the plasma for the 
experiment were as follows: 

ion constituents — neon (Ne+) and krypton (Kr+) 
mass ratio — M(Kr+ )/M(Ne+) = 4.1 

drift energy — Ed(Ne+) = 20-25 eV and Ed(Kr+) = 85-95 eV 

ambient density — n = 0.1-1.1E5 cm(-3) at ~ 70 cm from source 

ion component ratio — n(Ne+ ) /n(Kr+ ) = variable 

electron temperature — Te = 3000-4000 K 

plasma space potential — 2-3 volts 

ion temperature — Ti < Te. 

Three cases of ion density ratios were treated in the 
experiment: n(Ne+ ) /n(Kr+ ) = 2.0, 0.5, 0.2. In the wake of the plate 
for each case, relative motion between the light mass (Ne+) and the 
heavy mass (Kr+) is observed to increase somewhat as the density of 
Ne+ decreases. The normal component of the Ne+ velocity, relative to 
the flow direction incident at the plate, attains values greater than 
the ion acoustic speed in the ambient plasma due to the electric 
field generated from space charge effects in the plasma-plate edge 
boundary region. The normal velocity component for Kr+ barely 
reaches supersonic speeds at the farthest measurement locations. 

The filling of the wake region is analogous to the processes 
involved in the 'plasma expansion into a vacuum' . For the single ion 
plasma case this has been recently demonstrated by Wright et al. 

(Ref. 7,8). Results of the binary plasma experiment are consistent 
with some of the theoretical predictions of binary ion expansion. 


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however, the present beam conditions allow only a limited comparison. 
Data are still being analyzed, and the experiment and results are 
being documented (Ref. 9). 


PERSONNEL 


Dr. Gordon R. Wilson has joined our group as a Research 
Associate. He recently received his Ph. D. (Ref. 10) from Brigham 
Young University. He will augment our capabilities in both numerical 
modeling and data analysis. 


MEETINGS 


Dr. Comfort participated in the NSF Workshop on Solar 
Terrestrial Physics, August 6-8, 1987 in Seattle, WA. He also 
attended the I AGA/IUGG Meeting in Vancouver, Canada, August 9-22, 
1987, where he presented a paper on ion composition (Ref. 2) and an 
invited paper (Ref. 11) on plasmasphere-ionosphere coupling for Dr. 
Horwitz, who was unable to attend. Drs. Comfort and Horwitz attended 
the Workshop on Experiments with Magnets in Low Earth Orbit Using 
Space Plasma Laboratory Diagnostics, September 15-16, 1987, 
Huntsville, AL. Dr. Horwitz was a co-author on a paper on dynamics 
of reconnected flux tubes, presented to the Spring AGU Meeting (Ref. 
12 ) . 


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PUBLICATIONS 


in addition to the papers noted above, the following papers are 
at the indicated stage of the publication cycle: 

* Papers published during this period are those on: the 
geomagnetic spectrometer in the magnetotail lobes (Ref. 13), 0++ in 
the plasmasphere (Ref. 14), invited IUGG report on core plasma in the 
magnetosphere (Ref. 15), plasmasphere and plasmapause characteristics 
(Ref. 16), models of plasmaspher ic plasma distributions (Ref. 17), 
plasmasphere thermal structure (Ref. 18), electron temperature 
enhancements in satellite wakes (Ref. 19), ring current effects on 
SAR arc formation (Ref. 20), conical ion distributions near 1 RE 
(Ref. 21), solar wind control of the geomagnetic mass spectrometer 
(Ref. 22), ATS -6 record charging events (Ref. 23), and SCATHA 
potential modulations (Ref. 24). 

* Papers accepted for publication and in press are those on: heavy 
ion enhancements in the outer plasmasphere (Ref. 25), tail lobe ion 
spectrometer (Ref. 26), MHD wave speeds in the inner magnetosphere 
(Ref. 27), perpendicular ion heating effects on refilling (Ref. 28) 
magnetic mirror force (Ref. 29), kinetic approach in global plasma 
transport modeling (Ref. 30), particle and field signatures 
associated with SAR arc field lines (Ref. 31), electron beam 
experiments at high altitudes (Ref. 32), modeling with an outer 
plasmasphere heat source (Ref. 33), statistical models of equatorial 
trapped plasma (Ref. 34), dynamical evolution of low energy ions in 
Earth's magnetosphere (Ref. 35), statistical survey of plasmaspher ic 


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ion properties (Ref. 36), high altitude electron beam experiments 
(Ref. 37), and broadband electrostatic noise near the shuttle orbiter 
(Ref. 38). 

* Papers submitted for publication and in review are those on: 
centrifugal ion acceleration in the polar ionosphere (Ref. 39), and 
plasmapause signatures in P-region electron temperature signatures 
(Ref. 6). 



Richard H. Comfort 



James L. Horwitz 


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REFERENCES 


1. Comfort, R. H., P. D. Craven, D. L. Gallagher, R. L. West, c. R. 
Chappell, Spacecraft potential dependence on plasma density and 
its application to DE-l/RIMS density analysis, to be submitted 
to J. Geophvs. Res. . 1987. 

2. Comfort, R. H., I. T. Newberry, C. R. Chappell, Variations of 
thermal ion composition in the plasmasphere with geomagnetic 
activity, submitted for presentation to the 19th IUGG General 
Assembly, August 9-22, 1987, Vancouver, Canada. 

3. Samir, U., R. H. Comfort, N. H. Stone, and K. H. Wright, Jr., A 
comparison between plasma wake models for plasmaspher ic and 
ionospheric conditions. Planet. Space Res. , in press, 1987. 

4. Samir, U., R. H. Comfort, C. R. Chappell, N. H. Stone, 
Observations of low-energy ions in the wake of a magnetospher ic 
satellite, J . Geophvs . Res . . 91 . 5725, 1986. 

5. Samir, U., R. H. Comfort, N. Singh, K. S. Hwang, and N. H. 

Stone, Expansion of a space plasma into the wake of a 
plasmaspher ic satellite: theory/experiment comparison, to be 
submitted to Phvs . Rev . Lett . . 1987. 

6. Brace, L. H., C. R. Chappell, R. H. Comfort, M. 0. Chandler, and 
J. L. Horwitz, F-region electron temperature signatures of the 
plasmapause based on Dynamics Explorer 1 and 2 measurements, 
submitted to J. Geophvs . Res. . 1987. 

7. Wright, Jr., K. H., N. H. Stone, and U. Samir, A study of plasma 
expansion phenomena in laboratory generated plasma wakes: 
preliminary results, J. Plasma Physics . 33 . 71, 1985. 

8. Wright, Jr., K. H., D. E. Parks, I. Katz, N. H. Stone, and U. 
Samir, More on the expansion of a collisionless plasma into the 
wake of a body. J. Plasma Physics . 35 , 119, 1986. 

9. Wright, Jr., K. H., A study of single and binary ion plasma 
expansion into laboratory generated plasma wakes, Ph. D. 
Dissertation, University of Alabama in Huntsville, in 
preparation, 1987. 

10. Wilson, G. R., Simulation of the plasma interaction with thin 
dust clouds, Ph. D. Dissertation, Brigham Young University, 

1987. 

11. Horwitz, J. L., R. H. Comfort, L. H. Brace, M. 0. Chandler, C. 

R. Chappell, W. B. Hanson, J. U. Kozyra, Dynamics Explorer 
measurements of plasmasphere-ionosphere coupling near trough 
flux tubes, presented to the 19th IUGG General Assembly, August 
9-22, 1987, Vancouver, Canada. 


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12. Saflekos, N., J. L. Burch, M. Sugiura, D. A. Gurnett, and J. L. 
Horwitz, Observations of reconnected flux tubes within the 
midaltitude cusp, EOS Transactions of the American Geophysical 
Union. 68, 383, 1987. 

13. Horwitz, J. L., Geomagnetic spectrometer in the magnetotail 
lobes. Chapman monograph on Magnetotail Physics , ed. A. T. Y. 
Liu, Johns Hopkins Press, p. 291, 1987. 

14. Chandler, M. 0., J. J. Ponthieu, T. E. Cravens, A. F. Nagy, and 
P. G. Richards, Model calculations of minor ion populations in 
the plasmasphere, J . Geophys . Res . . 92 . 5885, 1987. 

15. Horwitz, J. L., Core plasma in the magnetosphere. Rev. Geophys.. 
25, 579, 1987. 

16. Horwitz, J. L., R. H. Comfort, and C. R. Chappell, Plasmasphere 
and plasmapause region characteristics as measured by DE-1, Adv. 
Space Res . . 6., 21, 1987. 

17. Torr, D. G., P. G. Richards, J. L. Horwitz, and M. R. Torr, 
Models of the plasmaspher lc thermal plasma distribution. Adv. 
Space Res . . 6, 151, 1987. 

18. Comfort, R. H., Plasmasphere thermal structure as measured by 
I SEE-1 and DE-1, Adv. Space Res.. 6., 31, 1987. 

19. Singh, N., U. Samir, K. H. Wright, Jr. and N. H. Stone, A 
possible explanation of the electron temperature enhancement in 
the wake of a satellite, J. Geophys. Res.. 92, 6100, 1987. 

20. Kozyra, J. U., E. G. Shelley, R. H. Comfort, L. H. Brace, T. E. 

Cravens and A. F. Nagy, The role of ring current 0+ in the 

formation of Stable Auroral Red arcs, J. Geophys. Res.. 92 . 

7487, 1987. 

21. Olsen, R. C., and C. R. Chappell, Conical ion distributions near 
one earth radius, Adv. Space Res. . 6, 117, 1986. 

22. Waite, Jr., J. H., M. Lockwood, T. E. Moore, M. O. Chandler, J. 

L. Horwitz, and C. R. Chappell, Solar wind control of the 

geomagnetic mass spectrometer. Solar Wind-Magnetosphere 
Coupling , Terra Scientific Publishing Co., p. 707, 1986. 

23. Olsen, R. C., The record charging events from ATS-6, J . 
Spacecraft Rockets . 24 . 362, 1987. 

24. Craven, P. D., R. C. Olsen, J. Fennell, D. Croley, and T. 

Aggson, Potential modulations on the SCATHA spacecraft, J . 
Spacecraft Rockets . 24 . 150, 1987. 

25. Roberts, W. T., Jr., J. L. Horwitz, R. H. Comfort, J. H. Waite, 
Jr., J. L. Green, and C. R. Chappell, Heavy ion enhancements in 
the outer plasmasphere, J. Geophvs. Res. , in press, 1987. 


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26. Candldl, M . , s. Orslni, and J. L. Horwitz, The tail lobe ion 
spectrometer: theory and observations, J . Geophvs . Res . . in 
press, 1987. 

27. Moore, T. E., D. L. Gallagher, J. L. Horwitz, and R. H. Comfort, 
MHD wave breaking in the outer plasmasphere, Geophvs. Res. 

Lett . , in press, 1987. 

28. Singh, N., and K. S. Hwang, Perpendicular ion heating effects on 
the refilling of the outer plasmasphere, J. Geophvs. Res. , in 
press, 1987. 

29. Comfort, R. H., The magnetic mirror force in plasma fluid 
models. Monograph on Huntsville Workshop on Magnetosphere 
Ionosphere Plasma Models, in press, 1987. 

30. Horwitz, J. L. The kinetic approach in global plasma transport 
modeling: advantages and difficulties. Monograph on Huntsville 
Workshop on Magnetosphere Ionosphere Plasma Models, in press, 
1987. 

31. Kozyra, J. U., T. E. Cravens, A. F. Nagy, D. A. Gurnett, R. L. 
Huff, R. H. Comfort, J. H. Waite, Jr., L. H. Brace, R. A. 
Hoffman, J. D. Winningham, J. L. Burch, and W. K. Peterson, 
Observations by the Dynamics Explorer satellites of new 
signatures in particle and field measurements associated with 
SAR arc field lines at magnetospher ic heights, Adv ♦ Space Res . . 
in press, 1987. 

32. Olsen, R. C., Electron beam experiments at high altitudes, J . 
Electrostatics . in press, 1987. 

33. Chandler, M. 0., J. U. Kozyra, J. L. Horwitz, R. H. Comfort, W. 

K. Peterson and L. H. Brace, Modeling of the thermal plasma in 
the outer plasmasphere: a magnetospher 1c heat source. Monograph 
on Huntsville Workshop on Magnetosphere Ionosphere Plasma 
Models, in press, 1987. 

34. Olsen, R. C., and C. R. Chappell, Statistical models of 
equatorial trapped plasma. Monograph on Huntsville Workshop on 
Magnetosphere Ionosphere Plasma Models, in press, 1987. 

35. Giles, B. L., C. R. Chappell, J. H. Waite, Jr., T. E. Moore, J. 

L. Horwitz, Dynamic evolution of low energy ions in the 
terrestrial magnetosphere. Monograph on Huntsville Workshop on 
Magnetosphere Ionosphere Plasma Models, in press, 1987. 

36. Comfort, R. H., I. T. Newberry and C. R. Chappell, Preliminary 
statistical survey of plasmaspher ic ion properties from 
observations by DE-l/RIMS, Monograph on Huntsville Workshop on 
Magnetosphere Ionosphere Plasma Models, in press, 1987. 


37. Olsen, R. C., and H. A. Cohen, Electron beam experiments at high 
altitudes, Adv. Space Res. , in press, 1987. 


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38. Hwang, K. S., N. H. Stone, K. H. Wright, Jr., and U. Samir, the 
emissions of broadband electrostatic noise in the near vicinity 
of the shuttle orbiter. Planet. Space Scl.. in press, 1987. 

39. Swinney, K., J. L. Horwitz, and D. Delcourt, Centrifugal 
acceleration of ionospheric ions in the polar magnetosphere, 
submitted to J . Geophvs . Res . . 1987. 


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