“SEMIANNUAL PROGRESS REPORT
/OH J /V2 — '
INVESTIGATION OF LOW ENERGY SPACE PLASMA
Richard H. Comfort
James L. Horwitz
National Aeronautics and Space Administration
George C. Marshall Space Flight Center
Marshall Space Flight Center, Alabama 35812
The University of Alabama in Huntsville
College of Science
Huntsville, Alabama 35899
(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
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
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.
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
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
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
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
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.
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).
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.
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 ) .
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
ion properties (Ref. 36), high altitude electron beam experiments
(Ref. 37), and broadband electrostatic noise near the shuttle orbiter
* 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
Richard H. Comfort
James L. Horwitz
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
10. Wilson, G. R., Simulation of the plasma interaction with thin
dust clouds, Ph. D. Dissertation, Brigham Young University,
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.
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 .
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.
26. Candldl, M . , s. Orslni, and J. L. Horwitz, The tail lobe ion
spectrometer: theory and observations, J . Geophvs . Res . . in
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
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,
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.
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.