PRODUCTION OF VIBRATIONALLY AND ROTATIONALLY EXCITED NO IN THE NIGHTTIME TERRESTRIAL THERMOSPHERE

A quantitative interpretation is given of the observed quiescent night time radiance of nitric oxide in the fundamental vibration-rotation ba nd near 5.3 mu m. The radiance measured in the space shuttle experimen t Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) is known to have two components, one characterized by a thermal popula tion of rotational levels and the other by a highly excited rotational population. The analysis presented here confirms that the thermal pop ulation is due to impact excitation of NO by atomic oxygen and attribu tes the highly excited distribution to the reaction of N(S-4) atoms wi th O-2. The measured nighttime emission profile is compared with predi ctions for several model atmospheres. Both sources of excited NO depen d upon the latitude, longitude, local time, and geomagnetic indices. T he fraction of vibrationally excited NO produced by the reaction of N( S-4) with O-2 increases rapidly with altitude from 130 to 200 km and i ts contribution to cooling, though much less than that from inelastic excitation of NO(nu=0) is, at higher altitudes, comparable to cooling produced by the atomic oxygen fine-structure line at 63 mu m.