Hot Fraction of Oxygen Atoms in the Polar Upper Atmosphere of the Earth

The hot oxygen geocorona is an integral and dynamic component in the polar regions of the Earth’s upper atmosphere. Its formation is determined by such sources of suprathermal oxygen atoms as the precipitation of high-energy auroral electrons and reactions of exothermic atmospheric chemistry, and its evolution is controlled by kinetic processes of thermalization and transport of suprathermal O atoms under conditions far from local thermodynamic equilibrium. In this study, the process of dissociation of molecular oxygen by auroral electrons has been studied in detail for the first time and its important contribution to the formation of the fraction of hot oxygen atoms in the polar upper atmosphere of the Earth has been established, since it is several times greater in magnitude than the contribution of the reactions of dissociative recombination of molecular ions usually taken into account in previous models of the oxygen geocorona, and is comparable in magnitude to the contribution of exothermic reactions of atmospheric chemistry. The author compared the altitude profile of the hot oxygen numerical density obtained in the calculations with the predictions of the empirical atmospheric model NRLMSIS-00. It was found that at altitudes near the exobase of ~500–600 km, the concentrations of “anomalous” oxygen predicted by the empirical model are close in magnitude to the calculated model concentrations of the hot fraction of atomic oxygen. This circumstance confirms the necessity of taking into account the hot fraction of oxygen in calculations of atmospheric drag of satellites in the polar regions of the Earth’s upper atmosphere.