given distance R is also shown. The energy content released into a given shell dominates the ambient energy content, however, since the streaming Ar+ kinetic energy is 3.5 keV and the ambient thermal energy is ~ 1 eV. Argon ion engine exhaust in the magnetosphere is thus unique in that it represents both matter and energy injections. The evolution of these two forms of injections follows very different paths, as we shall show. B. POTV Chemical Engine Exhaust Neutral chemical exhaust is initially emitted in the magnetosphere as H2O molecules in the exhaust of LO2/LH2 rocket engines of the POTV. In the magnetosphere, the H2O and H2 molecules are expected to be photodissociated into H and O atoms. Since chemical rocket combustion temperatures are ~ 2000° K, slightly less but comparable to the ambient magnetospheric temperature, chemical rocket exhaust does not represent injection of extra free energy, just injection of matter. The emission scenario of neutral chemical exhaust can be separated into two distinct phases: (1) dense neutral exhaust cloud expanding away from the rocket nozzle and (2) gravitational trapping in magnetospheric orbits or exit from the magnetosphere. The first phase is common to all chemical rocket burns and the emission model is characterized by a model of free jet expansion. The fate of neutral molecules and atoms in the second phase depends on the orbital dynamics of each engine burn: some burns procude neutral clouds which escape the magnetosphere through either its upper or lower boundaries, while other burns produce gravitationally trapped neutrals. We shall consider both phases of the emission scenario. 8
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