Linear modes in the partially ionized heliosphere plasma

Abstract

AbstractThe heliosphere is predominantly a partially ionized plasma that consists of electrons, ions and significant neutral atoms. Nonlinear interactions among these species take place through direct collision or charge-exchange processes. These interactions modify linear and nonlinear properties of the plasma. In this work, we develop a one-dimensional linear theory to investigate linear instabilities in such a system. In our model, the electrons and ions are described by a single fluid compressible magnetohydrodynamic (MHD) model and are coupled self-consistently to the neutral fluid via compressible hydrodynamic equations. The coupling is mediated by the charge-exchange process. Based on our self-consistent analysis, we find that the charge-exchange coupling is more effective at larger length scales, and the Alfvén waves are not affected by the charge-exchange coupling. By contrast, the fast and slow waves are driven linearly unstable.