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

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 Omega(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 WHe(+) may vanish, and waves near WHe(+) may be unstable. The maximum wave-number 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 (omega(pe)/vertical bar Omega(e)vertical bar > similar to 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. Citation: Chen, L., R. M. Thorne, and J. Bortnik (2011), The controlling effect of ion temperature on EMIC wave excitation and scattering, Geophys. Res. Lett., 38, L16109, doi:10.1029/2011GL048653.