Solutions to bi-Maxwellian transport equations for the polar wind

Abstract

In the past, the polar wind has been simulated using transport equations based on either a Maxwellian or a bi-Maxwellian velocity distribution function. Previous solutions obtained for both the Maxwellian-based 13-moment set of equations and the bi-Maxwellian-based 16-moment set of equations have indicated that these two approaches are in close agreement with each other. However, due to the numerical problems involved in solving the transport equations, the solutions obtained were few in number and represented only a small subset of the possible range of polar wind behavior. In this study, we obtained polar wind solutions for a broad range of O + density, H + drift velocity, electron temperature and H + temperature boundary conditions. We used the bi-Maxwellian-based 16-moment set of transport equations, since this set is expected to be superior to Maxwellian-based equations in describing large temperature anisotropies and heat flows. Our solutions corroborate the earlier results when similar boundary conditions are used. Also, for previously unexplored combinations of boundary conditions, our solutions are often qualitatively different from any obtained before.