4.4.4 Phenomenology Associated with Large Space Structures (Vondrak) In addition to the transportation system used between LEO and GEO and any possible effects due to microwaves (which are not considered here), another potential source of magnetospheric modification is provided by the SPS satellite structure itself. The satellite interacts with the magnetosphere in the following ways: 1. The structure will be a sink that absorbs particles striking it. This flux tube blockage is analogous to the sweeping of the Jovian radiation belts by the Galilean satellites. (See also Kesler and Cour-Palais, 1978). 2. The satellite will charge, probably to a negative potential, and the ambient ion population will be accelerated to it. 3. The structure wll be a localized source of IR and reflected visible light. This has been reviewed in a workshop held recently, whose report (Stokes, 1979) has not yet been published. See also Item F.4 of Appendix F. 4. The satellite will emit photoelectrons. These relatively cool electrons may interact with the ambient plasma. 5. The structure will be a source of contaminant gases that may form a ring of neutral gases at GEO, Neutral gases are also emitted at GEO by ACS thrusters. The interaction of such neutral gas molecules with the ambient plasma at GEO is not well understood. 6. Meteoritic impact and energetic particle sputtering of spacecraft sufaces may be a substantial source of particulate material at GEO. 4.4.5 A Ring of Neutral Gases Associated with the Satellite (Garrett) Vondrak (1977, 1979) has suggested that the possibility exists for the formation of a permanent ring of neutral gas around the earth. In Garrett and Forbes (1979), the likelihood of the formation of such a ring forming in geosynchronous orbit has been considered. The problem readily reduces to that of determining the ionization rate of the neutral cloud formed in the immediate vicinity of the emitter (the SPS satellite in this case). Over the long-term SPS mission, the major continuing contaminant would be neutral gas from the control thrusters. For Ar thrusters, given the current configuration, Garrett and Forbes find that the neutral cloud created would have a characteristic ionization time of 15 days. The Ar+ cloud created would have a maximum density of only 0.01 cm under normal conditions at the edge of a cloud 40 km in radius. Hence, the impact of the ions would be insignificant. The long ionization period, however, would allow a neutral ring with density of about 2 cm~J to form. The impact of this cloud is not clear. Likewise, the H2 and ^O emitted by the POTV may also contribute to such a ring. As existing analytic techniques are capable of estimating the distribution of such a cloud, it is recommended that this analysis be carried out.
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