NASA Scientific and Technical Aerospace Reports

Ionospheric plasma interaction effects on the International Space Station are discussed in the following paper. The large
structure and high voltage arrays of the ISS represent a complex system interacting with LEO plasma. Discharge current
measurements made by the Plasma Contactor Units and potential measurements made by the Floating Potential Probe
delineate charging and magnetic induction effects on the ISS. Based on theoretical and physical understanding of the
interaction phenomena, a model of ISS plasma interaction has been developed. The model includes magnetic induction effects,
interaction of the high voltage solar arrays with ionospheric plasma, and accounts for other conductive areas on the ISS. Based
on these phenomena, the Plasma Interaction Model has been developed. Limited verification of the model has been performed
by comparison of Floating Potential Probe measurement data to simulations. The ISS plasma interaction model will be further
tested and verified as measurements from the Floating Potential Measurement Unit become available, and construction of the
ISS continues.
Author
International Space Station; Plasma Potentials; Measure and Integration; Ionospheres; Mathematical Models
20040111049 NASA Marshall Space Flight Center, Huntsville, AL, USA
Ground-Based Simulation of Low-Earth Orbit Plasma Conditions: Plasma Generation and Characterization
Williams, John D.; Farnell, Casey C.; Shoemaker, Paul B.; Vaughn, Jason A.; Schneider, Todd A.; 8th Spacecraft Charging
Technology Conference; March 2004; 14 pp.; In English; See also 20040111031; No Copyright; Avail: CASI; A03, Hardcopy
A 16-cm diameter plasma source operated on argon is described that is capable of producing a plasma environment that
closely simulates the low Earth orbit (LEO) conditions experienced by satellites in the altitude range between 300 to 500 km.
The plasma source uses a transverse-field magnetic filter, and has been successful in producing low electron temperature
plasmas that contain streaming ion populations. Both of these characteristics are important because the plasma in LEO is
relatively cold (e.g., Te approx. 0.1 eV) and the ram energy of the ions due to the motion of the satellite relative to the LEO
plasma is high (e.g., 7,800 m/s which corresponds to approx. 5 eV for O+ ions). Plasma source operational conditions of flow
rate and discharge power are presented that allow the electron temperature to be adjusted over a range from 0.14 to 0.4 eV.
The expanding plasma flow field downstream of the source contains both low-energy, charge-exchange ions and streaming
ions with energies that are adjustable over a range from 4 eV to 6 eV. At low flow rates and low facility pressures, the
streaming ion component of the ion population comprises over 90% of the total plasma density. In the work described herein,
a large area retarding potential analyzer was used to measure both electron and ion energy distribution functions in the low
density, expanding plasma produced downstream of the plasma source. The benefits of using this type of plasma diagnostic
tool in easily perturbed, low-density plasma are identified, and techniques are also discussed that can be used to perform
real-time measurements of electron temperature. Finally, recommendations are made that may enable lower electron
temperatures to be produced while simultaneously decreasing the plasma source flow rate below 1 to 2 sccm.
Author
Low Earth Orbits; Plasma Generators; Plasmas (Physics); Simulation; Cold Plasmas; Argon Plasma; Magnetohydrodynamic
Flow; Flow Distribution
20040111064 Kyoto Univ., Japan
Particle-In-Cell Simulations on Antenna Characteristics in Magnetized Plasma
Usui, Hideyuki; Nakamura, N.; Kojima, H.; Matsumoto, H.; Omura, Y.; 8th Spacecraft Charging Technology Conference;
March 2004; 6 pp.; In English; See also 20040111031
Contract(s)/Grant(s): SR-12440131; No Copyright; Avail: CASI; A02, Hardcopy
We for the first time applied electromagnetic PIC (Particle-In-Cell) computer simulations to analyze the antenna
characteristics in magnetized plasma. In a three-dimensional simulation space, we placed a dipole antenna which is a
conducting current line in a magnetized plasma. By providing a Gaussian pulse as an input power to the center of the antenna
and observing the current induced at the power feeding point, we obtain the input impedance of the antenna as a function of
frequency. We particularly examined the electron kinetic effects on the antenna impedance such as electron temperature and
electron evacuated region (ion sheath) formed around the antenna. It is confirmed that the most obvious resonance point is the
local Upper Hybrid Resonance frequency. As the electron temperature increases, the resonance frequency also increases in
accordance with the modification of dispersion relation for the UHR branch. We also examined the antenna impedance
variation by changing the size of the electron evacuated region or ion sheath created around the antenna. We could confirm
that the antenna resonance near the local UHR frequency is sharp for the small sheath while the profiles of the impedance
approach to those of vacuum case as the sheath becomes large. The resonance frequency also decreases because the plasma
density also decreases in the vicinity of the antenna.
Author
Computerized Simulation; Dipole Antennas; Plasma Density
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