Modelled O2 airglow distributions in the Martian atmosphere
Résumé
We use a three-dimensional atmospheric model to study the airglow emissions from molecular oxygen in the Martian atmosphere. We estimate the O2 Herzberg I and II, the Chamberlain, and the Infrared Atmospheric band emissions from different sets of kinetic parameters available in the literature. As expected, the enhanced production of atomic oxygen during daytime leads to stronger emissions at 12 hour local time than at 00 hour local time. Nevertheless, at night, the strongest emissions are found in the subtropics and around the terminator where the photochemistry of atomic oxygen is more active. Among the simulated emissions, we find that the Infrared Atmospheric emission is the most intense, as expected, and has maximum intensity reaching a few megarayleighs over the poles during the equinoctial seasons, and an average intensity over the equatorial latitudes of 50 kilorayleighs. We investigate the impact of different levels of water and dust content on airglow and we observe that the airglow structure is modulated by variations in the background atmospheric conditions. Moreover, comparisons of the emission with observations from instruments on board Mars orbiters and with ground-based measurements from Earth allow us to validate the consistency of our airglow model. Finally, we observe that the emission profiles from all band systems show structures; a double-layer profile is very frequent, and is representative of the vertical distribution of the current measurements of O2 nightglow. This paper emphasizes the advantage of using three-dimensional global circulation models for the diagnostic of O2 photochemistry in CO2-dominated atmospheres.
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