Helium in the outer solar atmosphere

Abstract

We construct models of the outer solar atmosphere comprising the region from the mid chromosphere and into the solar wind in order to study the force and energy balance in models with a significant helium abundance. The corona is created by dissipation of an energy flux from the Sun. The energy flux is lost as radiation from the top of the chromosphere and as gravitational and kinetic solar wind energy flux. We find that in models with significant ion heating of the extended corona most of the energy flux is lost in the solar wind. The ion temperatures are higher than the electron temperature in these models, and the α-particle temperature is much higher than the proton temperature. Roughly speaking we find that the relative α-particle and proton fluxes are set by the degree of chromospheric mixing while the speeds are set by the details of the coronal heating process.