ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-25-2147-2007 Thermal structure and dynamics of the Martian upper atmosphere at solar minimum from global circulation model simulations Moffat-Griffin T. 1 2 Aylward A. D. 1 Nicholson W. 1 Atmospheric Physics Lab, University College London, UK now at: British Antarctic Survey, Cambridge, UK 06 11 2007 25 10 2147 2158 Copyright: © 2007 T. Moffat-Griffin et al. 2007 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/25/2147/2007/angeo-25-2147-2007.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/25/2147/2007/angeo-25-2147-2007.pdf

Simulations of the Martian upper atmosphere have been produced from a self-consistent three-dimensional numerical model of the Martian thermosphere and ionosphere, called MarTIM. It covers an altitude range of 60 km to the upper thermosphere, usually at least 250 km altitude. A radiation scheme is included that allows the main sources of energy input, EUV/UV and IR absorption by CO<sub>2</sub> and CO, to be calculated. CO<sub>2</sub>, N<sub>2</sub> and O are treated as the major gases in MarTIM, and are mutually diffused (though neutral chemistry is ignored). The densities of other species (the minor gases), CO, Ar, O<sub>2</sub> and NO, are based on diffusive equilibrium above the turbopause. The ionosphere is calculated from a simple photoionisation and charge exchange routine though in this paper we will only consider the thermal and dynamic structure of the neutral atmosphere at solar minimum conditions. The semi-diurnal (2,2) migrating tide, introduced at MarTIM's lower boundary, affects the dynamics up to 130 km. The Mars Climate Database (Lewis et al., 2001) can be used as a lower boundary in MarTIM. The effect of this is to increase wind speeds in the thermosphere and to produce small-scale structures throughout the thermosphere. Temperature profiles are in good agreement with Pathfinder results. Wind velocities are slightly lower compared to analysis of MGS accelerometer data (Withers, 2003). The novel step-by-step approach of adding in new features to MarTIM has resulted in further understanding of the drivers of the Martian thermosphere.

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