Generalized electron Bernstein modes in a plasma with a kappa velocity distribution

Perpendicularly propagating electron Bernstein modes in a uniformly magnetized plasma having an isotropic kappa velocity distribution are investigated within the framework of a fully electromagnetic plasma model but one which ignores particle relativistic effects. The dispersion relations for the Bernstein mode waves are found to be significantly dependent on the spectral index, κ, of the electron kappa distribution. In particular, waves with frequencies exceeding the upper hybrid frequency are seen to occupy a diminishing range of frequencies above the nearest cyclotron harmonic as κ is reduced. The Bernstein mode wave whose frequency lies closest to the upper hybrid frequency is found to couple to the cold plasma, electromagnetic Z mode, as it does in a Maxwellian plasma. For waves whose frequencies lie below the upper hybrid frequency, diminishing κ gives rise to an increasingly weak dependence of frequency on wave number and a slower frequency fall off with this parameter, but the frequency occupies the entire intraharmonic band here. All Bernstein modes are observed to become significantly electromagnetic at very long wavelengths, or small wave numbers, having in general elliptical polarization whose elliptical eccentricity depends on κ and wave number. At smaller wavelengths the modes are found to be electrostatic to a very good approximation, irrespective of κ value. The significance of the results to the interpretation of banded emissions in planetary magnetospheres is briefly discussed.