Wave propagation in a temperate multi-species plasma around the ion cyclotron frequency range

Abstract

Plane wave propagation in temperate plasmas consisting of n ion species is calculated analytically for collisionless plasmas of arbitrary composition. Numerical results are given for the complex refractive index of plasmas including collisions between particles of any kind and at arbitrary angles of propagation. There are two waves propagating at all angles other than 90°, one wave showing resonances at each of the n cyclotron frequencies of the ions involved. High ion-ion collision frequencies combine the motions of the ions to give new mass and composition weighted hybrid ion cyclotron resonances. At right angles to the external magnetic field one wave will propagate in the ion cyclotron range showing n – 1 ion-ion hybrid resonances and n – 1 hybrid cut-offs. The ion-ion hybrid resonances can be traced down to propagation at angles smaller than 90°, disappearing for parallel propagation. The hybrid resonance frequencies are close to the cyclotron frequencies of the ions with small relative concentrations. Damping of the waves in the neighbourhood of the ion-ion hybrid resonances is strongly affected by ion-ion collisions.