band. The (11-5) band should be stronger than the (10-4) band, the one observed in LAGOPEDO II. There is enough energy in the H20+ + e- reaction to populate all possible vibrational levels of OH. If, as seems likely, the OH band intensitities are in the kilorayleigh range, then it may be worthwhile to attempt to record spectra. It is possible that some of the infrared OH airglow is formed by reaction between H and 0^, and some from the NaD emissions that are correlated with the OH emissions. Simultaneous observations of the OH and NaD emissions could provide valuable diagnostics of mesospheric conditions (Takahashi et al., 1979, and other references cited therein). It seems quite possible that SPS rocket activities may give rise to noticeable airglow. Whether or not this is of environmental concern depends on its intensity, which is not predictable at the present time. It is important to field a set of airglow experiments for the September, 1979, HEAO-C launch. 2.11.6 Cloud Dispersion (Bernhardt) Only very limited data is available on the spreading of tracers in the mesosphere, and that is limited to relatively short times or small distances, see Fig. 3. In view of the potential importance of diffusing upward from the mesosphere, this deficiency may be significant, and should be re-examined. 2.11.7 Mesopheric NO (Turco) Ambient Nitric Oxide. NO concentrations have been measured in the mesosphere, mainly with rocket-borne instruments, and some of the recent values are shown in Fig. 4. Based on this data, there seems to be general agreement that an NO concentration minimum exists near 85 km at mid and low altitudes (although some data, e.g., Barth (1966) and Tisone (1973), do not show this minimum). Such a minimum can be understood in terms of the well- known photochemical reactions of NO: where the last reaction acts to conserve NO in competition with the second reaction. The natural sources of mesospheric NO include: upward transport from the middle stratosphere (30-40 km), where ^0 reacts with 0(^D) to form NO; downward transport from the thermosphere (above 90 km), where solar EUV and X-ray radiation ionizes and dissociates air molecules (Strobel, 1971); and meridional transport of NO from high latitudes, where it is produced by auroral activity and solar particle precipitation (Bauer, 1978). In addition, there is a worldwide source of mesospheric NO due to high velocity meteor ablation in the atmosphere (Park and Menees, 1978). For comparison, the
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