situations, for the POTV, are discussed in Section 3.1.3. Another situation is the deorbit burn of the HLLV, where most of the molecules are ejected with velocities sufficient for escape. If the molecules escape, we believe they can be forgotten, since they do not represent a significant H or 0 loss compared to that which occurs normally in nature. On the other hand, if they are trapped in orbits, they can react with H+ or 0+ ions, provided that they do not photodissociate first. At LEO altitudes the 0+ + 1^0 charge exchange reaction is considerably faster than the 1^0 photodestruction. Therefore, trapped exhaust molecules in LEO or in orbits passing through the 300-600-km altitude range will lead to destruction of ions, with consequent depletion of the F-layer and protonosphere. Such depletions will be very widespread spatially, but probably small in terms of percentages of ions removed because the absolute numbers of exhaust molecules injected in trapped orbits are comparatively small. 4.3 INJECTION OF keV PLASMA (Palmadesso) 4.3.1 Potential Consequences A. Alter radiation belt populations. Chiu et al. (1979) have argued that in the worst case (complete capture of the argon beam in the near magnetosphere, and long lifetime for the trapped argon) the hydrogen ion cyclotron instability that normally leads to scattering and precipitation of energetic electrons will be suppressed, thus allowing the electrons to increase in number until their population approaches an asymptotic upper limit. In this worst case scenario, the energetic electron density is increased by a factor of the order of 2. (See discussion by Davidson in Appendix F, item F.5.) B. Production of energetic argon ions via convection (HZE problem). By a process which is only partially understood at present, some oxygen and other ions injected into the magnetosphere are accelerated to very high energies. Adiabatic earthward convection energizes particles, but in order to be accelerated to extremely high energies the particles must move away from the earth without much energy loss and repeat this process several times. Other mechanisms that are thought to accelerate ions are interactions with ion cyclotron waves, electric fields along the magnetic field lines, and magnetospheric circulation forward to the magnetopause, to the magnetotail, and again forward to the inner magnetosphere. Presumably the number of particles accelerated to a given energy decreases rapidly as the energy increases. Thus the number of high Z argon ions that might be energized in this way is not now known. C. Gross change in plasmasphere composition and temperature. If the argon ion and energy injections in the magnetosphere are long-lasting, the temperature, density, and chemical composition of large portions of the inner magnetosphere may be altered substantially by the stopping of the Ar+ exhaust beam in these regions. The practical consequences of this, if any, are not known at present. Generally, however, an increase in plasma density stabilizes the radiation belts.
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