Instabilities of Obliquely Propagating Electromagnetic Modes in the Magnetosphere

Abstract

The oblique propagation of the ordinary and the extraordinary electromagnetic modes in the magnetosphere and the instabilities in these modes arising from temperature anisotropy are studied. The dispersion equation is solved numerically using a TDC 316 computer for (i) McIIwain parameter <i>L </i> = 2 and 3; (ii) temperature anisotropy ratio <i>δ</i> (= <i>T<img src='http://www.niscair.res.in/jinfo/line.gif' border=0>/T_II </i>) values varying from 10 to 0.1 and (iil) for wavelength of waves of the order of a kilometer. The computer calculations are carried out for frequencies in the range ω₁, to 3 ω₁, and ω₂ to 3 ω_2, where ω₁, and ω₂, are the left-hand and right-hand cut-off frequencies, and both the real as well as the imaginary parts of the wave vector are calculated. It is found that both the ordinary and the extraordinary electromagnetic waves are unstable and the instability shows a strong dependence on the propagation angle θ, McIlwain parameter <i>L, </i>propagation frequency and also on the temperature anisotropy ratio <i>δ</i>.