Absolute maxmum growth rates and enhancement of unstable electromagnetic ion–cyclotron waves in mixed warm–cold plasmas

We calculated relative and absolute maximum linear growth rates of the electromagnetic ion–cyclotron instability produced by the addition of cold plasma to an infinite uniform anisotropic plasma. In this, both accurate numerical solution of the linearized dispersion relation, and approximate analytic calculations, were carried out, and the results were compared critically.Qualitatively, results similar to those obtained in the past for the right-hand polarized electron–cyclotron electromagnetic (whistler) waves (Cuperman & Landau 1974) are found also for the left-hand polarized waves considered in this paper. Specifically, the electromagnetic ion–cyclotron instability in a warm, anisotropic proton plasma, characterized by Pp ≡ βP,A2p(Ap + 1) ≲ 1, may be significantly enhanced by addition of cold plasma.