Thermospheric 63-µm, emission of atomic oxygen in local thermodynamic equilibrium

Abstract

The 63-µm emission of atomic oxygen arising from the fine-structure transition (³P₁–³P₂) in the ground electronic state has been attributed to an important cooling mechanism of the thermosphere¹; however, the zenith-emission intensities measured by Grossmann and Offermann² were much weaker than those expected from the theoretical calculation³ based on local thermodynamic equilibrium (LTE). This discrepancy was interpreted by them to be due to a lower population temperature of O(³P_J) (J = 0, 1 and 2) rather than LTE. If this is true, the 63-µm emission is a much less important coolant of the thermosphere than has been believed. However, we have found that the formulation adopted by the previous calculation³ is inadequate. Based on an improved formulation we have made a LTE model calculation for O(³P_J) and found that calculated 63-µm zenith intensities would be consistent with those measured.