PLASMASPHERIC AND MAGNETOSPHERIC EFFECTS OF POTV AND COTV EFFLUENTS Y. T. Chiu Space Sciences Laboratory - The Aerospace Corporation P. 0. Box 92957 - Los Angeles, California 90009 This briefing deals with the current (FY80) progress in quantitative assessment of rocket engine exhaust effects of the Satellite Power System (SPS) in the magnetosphere and ionosphere. We shall consider argon ion engine effects for the cargo orbit transfer vehicles (COTV) and the LO^/LH^ chemical engine effects of the personnel orbit transfer vehicles (POTV). Both of these vehicles will make a number of trips between low earth orbit (LEO) and geosynchronous orbit (GEO) during the construction phase of each SPS. The long-term accumulative effects (if any) are presently unknown, and they depend on factors such as the number and scheduling of SPS spacecraft construction. Our quantitative assessment for FY80 is limited to the short term fate of the orbit transfer vehicle exhaust for the construction of a single SPS. Present knowledge of the effects of ion engine exhaust from the COTV has been reviewed in FY79. Dr. Don Rote's introductory remarks have touched upon them. The DOE/NASA baseline concept of July 1978 calls for use of argon ion engines of 3. 5 keV beam energy, which works out to be 130 km/sec in beam speed for the argon ions. This plasma exhaust cloud is thus moving across the magnetic field at ~ 1/10 of the Alfven speed in the plasmasphere, as depicted in Fig. 1. The plasmasphere and ionosphere feels the presence of this plasma cloud because it causes a pair of Alfven waves (shocks) to travel along the magnetic field lines down to the ionosphere, in much the same manner as the bow waves produced by a ship. Since these waves set the magnetospheric plasma in motion and since they also drive a conduction current in the ionosphere, the momentum of the argon beam is transferred to the magnetospheric and ionospheric plasma. This mechanism allows the major part of the beam momentum to be soaked up by the magnetospheric and ionospheric plasma, resulting not necessarily in a uniformly cold argon plasma, but in one with some hot argon plasma components trapped in the magnetic field due to pitch angle scattering. These hot components act much like an argon ring current. Numerical models of this process for realistic plasmaspheres have been constructed in FY80 and their results have essentially borne out these expectations. The essential point to be recognized is that the momentum transfer process takes place via the Alfven wave electric field, which moves through the plasmasphere at the Alfven speed (~ I 0 times the beam speed). Numerical calculations verify that the momentum transfer process has a time constant of < 20 sec. , so the argon beam has a length of ~ 2000 km. This mechanism is not new and has been considered for various processes by Drell, Foley and Ruderman (1965), by Zinn, Hoerlin and Petschek (1966), by Scholer (1970), and more recently by Kivelson and
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