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

Abstract

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 Ω He+. 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 Ω He+ may vanish, and waves near Ω He+ 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 (W pe /|Ω e | > ∼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. Copyright 2011 by the American Geophysical Union.