Landau damping in space plasmas

Journal Article · Thu Aug 01 00:00:00 EDT 1991 · Physics of Fluids B; (United States)

DOI:https://doi.org/10.1063/1.859624· OSTI ID:5666166

Thorne, R M ^[1]; Summers, D ^[2]

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1. Department of Atmospheric Sciences, University of California at Los Angeles, Los Angeles, California 90024-1565 (USA)
2. Department of Mathematics and Statistics, Memorial University of Newfoundland, St. John's, Newfoundland A1C 5S7 Canada (CA)

Space plasmas typically possess a particle distribution function with an enhanced high-energy tail that is well modeled by a generalized Lorentzian (or kappa) distribution with spectral index {kappa}. The modified plasma dispersion function {bold Z}{sup *}{sub {kappa}}({xi}) is employed to analyze the Landau damping of (electrostatic) Langmuir waves and ion-acoustic waves in a hot, isotropic, unmagnetized, generalized Lorentzian plasma, and the solutions are compared with the classical results for a Maxwellian plasma. Numerical solutions for the real and imaginary parts of the wave frequency {omega}{sub 0}{minus}{ital i}{gamma} are obtained as a function of the normalized wave number {ital k}{lambda}{sub D}, where {lambda}{sub D} is the electron Debye length. For both particle distributions the electrostatic modes are strongly damped, {gamma}/{omega}{sub 0}{much gt}1, at short wavelengths, {ital k}{lambda}{sub D}{much gt}1. This collisionless damping becomes less severe at long wavelengths, {ital k}{lambda}{sub D}{much lt}1, but the attenuation of Langmuir waves is much stronger for a generalized Lorentzian plasma than for a Maxwellian plasma. This will further localize Langmuir waves to frequencies just above the electron plasma frequency in plasmas with a substantial high-energy tail. Landau damping of ion-acoustic waves is only slightly affected by the presence of a high-energy tail, but is strongly dependent on the ion temperature. Owing to the simple analytical form of the modified plasma dispersion function when {kappa}=2 (corresponding to a pronounced high-energy tail), exact analytical results for the real and imaginary parts of the wave frequency can be found in this case; similar solutions are not available for a Maxwellian plasma.

• OSTI ID: 5666166
• Journal Information: Physics of Fluids B; (United States), Vol. 3:8; ISSN 0899-8221
• Country of Publication: United States
• Language: English

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