Solar wind from a corona with a large helium abundance

Observations of quasi‐steady high‐speed solar wind streams show that the proton mass flux density at 1 AU is remarkably constant, varying by less than 10% over long time periods. These observations are problematic, for simple theoretical models predict that the proton mass flux density is a sensitive function of the coronal base temperature, which is not expected to be unvarying to the degree required by the observations. In this paper we investigate the possibility that the presence of alpha particles in the coronal base region can reduce the sensitivity of the proton mass flux to the base temperature. The equations of mass and momentum conservation are solved for electrons, protons, and alpha particles using a variety of assumed temperature profiles for each species. A wide range of base conditions are considered. We find that for an alpha particle to proton density ratio at the base as small as 10%, alpha particles can reduce the sensitivity of the proton mass flux density to variations in the base temperature. We also study the effects of enhanced collisional coupling and of Alfvén waves on the flux of protons and alpha particles. As an aid to future observational determination of the alpha particle density in the corona, we present calculations of the intensities of the resonantly scattered lines He II λ304 and H I λ1216 for selected models.