III. ARGON ION ENGINE EXHAUST IN MAGNETOSPHERE Argon plasma exhaust from the COTV ion engine assembly is the major source of magnetospheric effects; therefore, this section sets the foundation for major tasks in this assessment effort. A complete and quantitative description of the evolution of the injected argon plasma from the initial beam stage to the final thermalized and recombined stage is a task probably beyond present scientific capability. Yet, a satisfactory picture of the evolution can be obtained by breaking it down into a collection of important phenomena taking place at various magnetospheric regions and in various stages of argon plasma evolution. In this Section, we shall concentrate on the interactions between the Ar+ exhaust and the magnetosphere as foundation for consideration of impacts in subsequent sections. As is noted in the Appendix and in Section II.A, the geometry of Ar+ beam injection and the likelihood of Ar+ precipitation into the atmosphere can be used roughly to divide the magnetospheric effects into two regimes. First, near LEO where the loss-cone is large a substantial portion of 3.5 keV Ar+ is likely to precipitate as a dense beam, stimulating artificial local airglow and atmospheric heating some orders of magnitude above the natural aurora. Second, in the plasmasphere (>= 2500 km altitude) and up to GEO, the loss-cone becomes small and the Ar+ beam is likely to undergo magnetospheric interactions as a plasma. In what follows we shall discuss the approximate behavior of the argon ion engine exhaust in these two regimes as groundwork for assessing the various specific magnetospheric effects. 13
RkJQdWJsaXNoZXIy MTU5NjU0Mg==