Understanding the variability of helium abundance in the solar corona using three-fluid modeling and UV observations

The variability of helium abundance in the solar corona and the solar wind is an important signature of solar activity, solar cycle, solar wind sources, as well as coronal heating processes. Motivated by recently reported remote sensing UV imaging observations by Helium Resonance Scattering in the Corona and Heliosphere (HERSCHEL) payload sounding rocket of helium abundance in inner corona on 14-Sep-2009 near solar minimum, we present the results of the first three-dimensional three-fluid (electrons, protons, alpha particles) model of tilted coronal streamer belt and slow solar wind that illustrate the various processes leading to helium abundance differentiation and variability. We find good qualitative agreement between the three-fluid model and the coronal helium abundances variability reported from UV observations of streamers, providing insight on the effects of the physical processes, such as heating, gravitational settling and inter-species Coulomb friction in the out-flowing solar wind that produce the observed features. The study impacts our understanding of the origins of the slow solar wind.
Comment: Accepted for publication in ApJL