The photochemistry of the MLT oxygen airglow emissions and the expected influences of tidal perturbations

Abstract

The photochemistry of the oxygen related nighttime airglow emissions of the upper mesosphere and lower thermosphere (MLT) region is reviewed. Emphasis is placed on the details of the reaction kinetics involved and the overall kinetic equations relating specific airglow emission rates to the densities of both the minor atmospheric species and the background atmospheric density. From an analysis of the overall molecularities of the emissions, we show how certain airglow features, such as the UV O 2( A 3 Σ u +) Herzberg I bands, respond primarily to changes in the local atomic oxygen density, whilst other emissions, such as the near-IR OH Meinel bands, respond to changes in both the oxygen atom densities and the background atmosphere. The implications for using airglow observations to monitor tidal perturbations of the MLT minor species densities are discussed.