The controlling effect of ion temperature on EMIC wave excitation and scattering

Abstract

[1] The dispersion relation of parallel propagating EMIC waves is investigated in a magnetized homogeneous plasma consisting of hot H+ and He+ ions. We demonstrate that the hot plasma effects associated with He+ and H+ significantly modify the cold plasma dispersion relation, especially near ΩHe+. For plasmas with a sufficiently small fraction of warm He+ and a sufficiently dense, hot and anisotropic H+ population, the cold plasma stop band above ΩHe+ may vanish, and waves near ΩHe+ may be unstable. The maximum wavenumber for unstable L-mode waves due to the hot plasma modification is used to identify the plasma conditions required for EMIC wave scattering of MeV electrons. We conclude that relatively extreme conditions (ωpe/|Ωe| > ∼25, and H+ anisotropy >1) are required for resonance with electrons near 1 MeV, which limits such scattering only to the region just inside the plasmasphere or storm time plumes.