J. O. Wise

Global variation in the 2.7 µm NO overtone limb-emission from the lower thermosphere

The overtone vibration-rotation band (Δv=−2) limb-emission from NO around 2.7 µm observed by the Cryogenic Infrared Radiance Instrumentation for Shuttle (CIRRIS-1A) at 120 km tangent altitude is shown to arise from the nascent molecule produced by the reactions of N(4S) and N(²D) atoms with O2. Measurement of the 2.7 µm emission from NO therefore permits modeling of the local rate of production of NO, a quantity important in odd nitrogen chemistry in the thermosphere. The 2.7 µm limb-radiance in the nonauroral region is observed, above the instrument noise level, only during the day and shows about a factor of 2 variation indicating a similar variation in the rate of production of NO. In the aurorally dosed region however the observations lead to about an order of magnitude variation in this rate.