For a given source strength, with a fraction AC of the circumference C of the orbit lying within the region of enhanced density, we have Ap « (AC) , AT a AC, and hence 6(Az)a (AC) Thus, the more extended the density enhancement the less is the drag enhancement, given that the satellite passes through the region of enhancement. Of course, the smaller AC is, the easier can the enhanced region be avoided. Determination of the significance of drag effects is thus equivalent to determining the change in mean density. Possible mechanisms for enhancement in p are: 1. Deposition of 0 and O2 from the HLLV. 2. Heating of the thermosphere by direct HLLV exhaust heating, or from the exothermicity of the dissociative recombination reactions of the ionized HLLV exhaust, such as H20+ + e . 3. Heating of the polar regions caused by argon deposition in the plasmasphere. The deposition moves the plasmapause outward and thus moves the precipitation to higher latitudes. If the precipitation remains constant, the resulting concentration of precipitation towards the pole could increase the heating of polar regions. The increase in polar heating would increase Ap and hence the drag, which may adversely affect the orbital lifetime of polar orbiting satellites. In summary, what needs to be done is: 1. to determine the steady state magnitude of Ap, given the SPS transportation requirements; and 2. to determine the horizontal spatial extent of the region of enhanced density, in which Ap 0. 3.4 AIRGLOW (Turco) The release of ^0 and in the mesosphere and thermosphere will lead to changes in the hydrogen and oxygen balances of these regions. As a result, alterations in airglow emissions are anticipated. The most obvious candidate for change is the OH infrared band system (~ 0.6-3.0 pm). Other emissions that might be affected include the O^D) and 0(^5) red (630 nm) and green (557.7 nm) lines, and^t^e singlet molecular oxygen atmospheric band of 02(iA ) at 1.27 pm and of 0^( I )at 0.76 pm. The atomic oxygen singlets are expected to be influenced by i§n chemistry (e.g., OH + e H + 0*), while the molecular oxygen singlets may be affected by changes in odd-oxygen chemistry (e.g., 0 + OH, 0 + 0 +_M, and 0^ + hv reactions). Finally, enhanced UV and IR radiation from NO, NO and N(ZD) may occur in reentry plumes in which air is heated to several thousand degrees Kelvin and N and NO are produced in large amounts (see Park and Menees, 1978).
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