Numerical simulations of ion and electron temperatures in the ionosphere of Mars: Multiple ions and diurnal variations

Abstract

This study shows how ion and electron temperatures in the ionosphere of Mars, which affect plasma densities, vary with altitude and time of day. These new results can be used to support the interpretation of existing and anticipated measurements of ionospheric conditions. Here, a one-dimensional fluid model of the martian ionosphere has been coupled to a kinetic supra-thermal electron transport model in order to self-consistently calculate ion and electron densities and temperatures. The models include diurnal variations, revealing hundreds of degrees Kelvin changes in dayside electron and ion temperatures at fixed altitude. The models treat each ion species separately, revealing hundreds of degrees Kelvin differences between H+ and O2+ temperatures. The coupled models also include an adiabatic expansion term into the heating equation, which contribute significantly to temperatures of lighter ions. Consistent with previous studies using single-ion plasma, solar EUV heating alone is insufficient to heat the thermal electrons and ion species to observed temperatures, indicating the presence of additional heating sources. Best agreement with measurements is found when additional topside heating fluxes of 15×109 and 2×107eVcm−2s−1 produce topside heating rates that are 35 and 100 times higher than the nominal solar heating rate for electrons and ions, respectively.