## Abstract

The paper presents analytic and numerical calculations of the absolute maximum growth rates and enhancement of the electromagnetic ion-cyclotron instability in mixed warm-cold plasmas. For a plasma system consisting of warm and anisotropic protons (β_{p} = 8πn_{p, w} KT_{II, P}|B^{2} _{0}≠0, A_{p}≡T _{⊥, P}|T_{II, p}—1≠ 0) and cold protons, the following hold: (i) The growth rate of any mode x ≡ω_{r}/Ω_{p} is maximized for a relative cold plasma concentration n_{p, c} /n_{p, w}= [(1-x)^{3}/1.5β_{p}χ^{2}]-1. (ii) The absolute maximum growth rate occurs for an optimum n_{p, c} /n_{p, w} value about [16/3β_{p}(A_{:p}+ 2)]—1. (iii) A significant enhancement occurs only if P_{p} =β_{p}A_{ 2p}(A_{p}+ 1) < 1. The enhancement decreases exponentially with increasing P_{p}values, (iv) But, in all cases with n_{p, c} /n_{p, w}0, the instability range in k space is increased by a factor of about (1 +n_{p, c} /n_{p, w} ^{½}. The paper also presents simple analytical (approximate) expressions for maximum growth rates and enhancement, as well as for the optimum relative cold plasma concentrations.

Original language | English |
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Pages (from-to) | 259-272 |

Number of pages | 14 |

Journal | Journal of Plasma Physics |

Volume | 13 |

Issue number | 2 |

DOIs | |

State | Published - Apr 1975 |