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

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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DAMPING
DISPERSION RELATIONS
DISTRIBUTION FUNCTIONS
FLUIDS
FULLY IONIZED GASES
FUNCTIONS
GASES
HOT PLASMA
ION ACOUSTIC WAVES
ION WAVES
IONIZED GASES
ISOTROPY
LANDAU DAMPING
LORENTZ GAS
MODIFICATIONS
PLASMA
PLASMA WAVES
SPACE