Numerical models of the Martian coupled thermosphere and ionosphere

Abstract

Two and three dimensional models of the Martian upper atmosphere and ionosphere have been developed to study the dynamics, temperature and composition of its neutral and plasma regimes. Three major neutral species - CO 2, N 2 and O are considered, together with a number of minor species CO, NO, Ar, O 2, and O 3. The density distributions of the ion species CO 2 +, N 2 +, O +, CO +, NO +, Ar + and O 2 + are also calculated explicitly. The models solve the time-dependant momentum, energy, continuity and three constituent composition equation self-consistently. The ionosphere is also calculated self-consistently including solar production, chemical sources and sinks and transport. Minor species chemistry and transport are included as well as a comprehensive radiation scheme, including radiative transport between the atmospheric layers. It has been found that the absorption of solar infra-red radiation must be included in order to maintain the temperature of the Martian mesopause. It has also been found that consideration of the day to night compositional variation is necessary for an accurate analysis of the heat conduction and viscosity terms. The models predictions have been compared with experimental observations, mainly from the VIKING space mission, with generally good agreement for major and minor neutral species, and for the ionospheric constituents.