Gyrokinetic Theory of Low-frequency Electromagnetic Waves in Finite-$\beta$ Anisotropic Plasmas

Abstract

We present a gyrokinetic theory for the electromagnetic waves and instabilities with frequencies much lower than the ion cyclotron frequency in finite-$\beta$ anisotropic uniform plasmas. Here, $\beta$ is the ratio between plasma and magnetic pressures. Kinetic effects due to both the finite Larmor radii and wave-particle resonances are fully kept in the analysis. Corresponding linear dispersion relation and wave polarizations, valid for general $\beta$ value and perpendicular wavelength, are then specifically derived for a bi-Maxwellian plasma. Analytic expressions for the criteria of kinetic firehose and mirror instabilities are also given. The mode frequency, stability, and wave polarization of a broad spectrum of normal modes are then investigated numerically in a systematic study over a set of parameters. Our study clearly demonstrates that, due to the finite ion Larmor radius effect, the ion-sound wave, mirror mode, and shear Alfven wave are intrinsically coupled.

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• Magnetic fluctuation power near proton temperature anisotropy instability thresholds in the solar wind
• Astrophysical Gyrokinetics: Basic Equations and Linear Theory
• Multi-Species Measurements of the Firehose and Mirror Instability Thresholds in the Solar Wind
• Inertial-Range Kinetic Turbulence in Pressure-Anisotropic Astrophysical Plasmas
• On locating the zeros and poles of a meromorphic function

Cited by in corpus (2)

• On locating the zeros and poles of a meromorphic function
• A kinetic CMA diagram