to the plasmasphere. The difference is not only quantitative but is also qualitative: the energy spectra of the argon ions deposited in the plasmasphere are dissimilar. For the ion cloud process accompanied by a weaker plasma instability loss process the solid line in Figure 5 gives a qualitative indication of the energy spectra of the argon ions. In the ion cloud model, most of the energy of the argon ions is dissipated in producing ionospheric currents caused by the cloud's field line dragging. This process yields the low energy peak. The higher energy tail and peak just below the injection energy of ^5 keV would be produced by various instability processes. In contrast, the sheath loss model shown by the dotted line in Figure 5 results in the argon ions being deposited with energies near the injection energy. The different beam stopping mechanism can produce very different environmental impacts. The sheath loss model predicts a large injection of energetic anisotropic argon ions which will drive plasma instabilities which may produce sufficient^scintillation to impair radio communications with geosynchronous satellites0. The partial depletion by precipitation of the energetic ion belts surrounding the earth is also possible due to the pitch angle scattering caused by argon ion turbulence. Cold argon ions (T MeV) would result in the sheath loss model only via the loss of energy by plasma instability mechanisms and electron coulomb scattering. Since during the energy degradation processes, argon ions will be lost by charge exchange and precipitation, the cold Ar plasma from the sheath loss mechanism will be much less than from the ion cloud mechanism. The environmental effects due to cold Ar would be greatly reduced in th^ sheath loss picture as well as those effects due to ionospheric cur- rents \ Finally, we note that in searching for observational support for ion beam stopping, the observations must correspond closely to the ion beam parameters envisioned for the COTV's. Specifically, the V^, AV^ and the initial be^m density and direction must be close to those planned for the COTV thrusters . Arguments that barium release observations or high altitude nuclear blasts give evidence supporting a given beam model are therefore not valid. A far better experimental test would be a Space Shuttle-born ion beam experiment. This could be a scaled down COTV ion thruster with power levels of about a kilowatt and a nozzle diameter of a few centimeters rather than a megawatt and a meter. The other beam parameters could be the same as for a COTV. The required power levels could be within the limits of the planned solar powered auxiliary 20kW orbiter integral solar array or the 6kW orbiter mounted array. Chiu, Y. T., J. G. Luhmann, B. K. Ching and D. J. Bouchen, Jr., An Equilibrium model of Plasmaspheric Composition and Density, J. Geophys. Res., 84, 909, 1979. ^Chen, A. J., J. M. Grebowsky and K. Marubashi, Diurnal Variations of Thermal Plasma in the Plasmasphere, Planet. Space Sci., 24, 765, 1976. 2 Curtis, S. A. and J. M. Grebowsky, Energetic Ion Beam Magnetosphere Injection and the Solar Power Satellite, J. Geophys. Res., in press, 1980. 4Chiu, Y. T., J. G. Luhmann, M. Schultz and J. M. Cornwall, Effects of Construction and Operation of a Satellite Power System Upon the Magnetosphere, Aerospace Report No. ATR-80 (7824)-1, 1 December 1979. Ichimaru, S., Basic Principles of Plasma Physics: A Statistical Approach, W. A. Benjamin, Inc. (Advanced Book Program) Reading, Mass., 1973. 6Curtis, S. A. and J. M. Grebowsky, Changes in the Terrestrial Atmosphere - Ionosphere-Magnetosphere System due to Ion Propulsion for Solar Power Satellite Placement, submitted to Space Solar Power Review, 1979.
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