Radial density, velocity and temperature profiles in a multi-species solar wind close to the coronal base: A self-consistent four-species model

Abstract

We present a multi-species model of the solar wind close to the coronal base. Employing a five-moment approximation, the steady state profiles of densities, velocities as well as temperatures of electrons and three ion species, namely protons, alpha particles and a minor ion population such as oxygen, are obtained self-consistently for a region close to the base of the corona. As none of these species is treated as a test particle population, the approach represents a full four-species model. In order to incorporate information that comes out of the kinetic non-equilibrium state of the coronal plasma, the transfer integrals describing the exchange of momentum and energy due to Coulomb collisions are solved for non-Maxwellian velocity distributions. Their moments yield generalized exchange terms required for a description of the plasma formulated at a hydrodynamic level. Since non-equilibrium velocity distributions cannot be obtained from a hydrodynamic treatment, their influence on the expansion of the multi-species solar wind and, in particular, on the thermal and non-thermal heating and cooling rates is investigated using a parameterised approach.