Thermalization of O(1D) atoms in the thermosphere
Shematovich, V. I. Gerard  J.- C., Bisikalo  D. V., Hubert  B.
J. Geophys. Res., 1999, 104, No. A3, 4287-4295.


Measurements of the Doppler width of the 6300 {\AA} airglow emission line have been extensively used to determine the thermospheric temperature. This technique is based on the assumption that the bulk of the emitting O($^1$D) atoms are thermalized in the region of the airglow source (200-300 km). A Monte Carlo stochastic model is used to calculate the energy distribution function of O($^1$D) atoms in the dayand nighttime thermosphere. Hot O($^1$D) atoms are produced by exothermic processes and their thermalization is controlled by the competition between radiation, collisional quenching and relaxation. It is found that the O($^1$D) temperature departs from the background gas temperature not only in the upper thermosphere but also in the region of the bulk 6300 {\AA} emission. At 300 km, for low solar activity conditions, the model predicts an excess O($^1$D) temperature of $\sim$ 180 K during daytime and $\sim$ 950 K at night. The temperature departure persists at lower altitudes as a result of the major contribution of the O$_2^+$ dissociative recombination source of hot $^1$D atoms. Experimental evidence based on the Fabry-Perot interferometer measurements on board the Dynamics Explorer satellite confirms the existence of an O($^1$D) temperature excess over the MSIS value. It is concluded that temperatures deduced from the 6300 {\AA} airglow line width exceed the ambient gas temperature by an amount which may be significant.