Effects of solar wind composition, anisotropy, and streaming on ordinary mode electromagnetic instability

Abstract

The stability of the low-frequency waves (ω < Ωi) propagating transverse to the magnetic field of the plasma, which is composed of electrons, protons, and α particles with anisotropic electron and ion temperatures, is explored. The threshold for the ordinary mode instability and the growth rates have a very strong dependence on the electron temperature anisotropy but have a comparatively weaker dependence on the ion temperature anisotropy, on the relative abundance of helium to hydrogen, and on the relative streaming of two ion species. The threshold for the instability of these low-frequency waves is (me/mp)½ times smaller than the one corresponding to high-frequency waves; however, for the relative abundance of helium to hydrogen up to 20% for the relevant known magnetic fields, particle densities, temperatures, and drifts, the solar wind remains below the threshold for this instability.