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Oblique propagation of electromagnetic waves in a kappa-Maxwellian plasma

Authors
  • Cattaert, Tom
  • Hellberg, Manfred A.
  • Mace, Richard L.
Publication Date
Jan 01, 2007
Source
Ghent University Institutional Archive
Keywords
Language
English
License
Unknown
External links

Abstract

Space plasmas are often observed to contain more particles in the high-energy tail than the usual Maxwellian distributions, and are well modeled by kappa distributions. The hybrid kappa-Maxwellian distribution and associated generalized plasma dispersion function Z(kappa M) were recently introduced to model magnetized space plasmas. The susceptibility tensor for a kappa-Maxwellian plasma component is derived, making use of Z(kappa M). This enables one to make general studies of obliquely propagating electromagnetic waves in a magnetoplasma. The susceptibility and dielectric tensors reduce to the Maxwellian expressions in the limit kappa ->infinity. As an illustration, the formalism is applied to the lower branch of the R mode and its off-parallel variant. For low kappa values, low-wavenumber, low-frequency parallel whistler waves are shown to be stable, unlike the Maxwellian case, which is unstable if the perpendicular temperature exceeds the parallel temperature. A numerical study is made of the effects of the value of kappa, the propagation angle, and the temperature anisotropy ratio on dispersion and damping. The kappa-Maxwellian distribution with very low kappa is found to be unstable in an overdense plasma near the electron-cyclotron frequency even when the parallel and perpendicular temperatures are equal, because of the anisotropy of the contours in velocity space.

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