A new tool for analyzing microinstabilites in space plasma modeled by a generalized Lorentzian (Kappa) distribution
- Memorial Univ. of Newfoundland, St. John`s (Canada)
- Univ. of California, Los Angeles, CA (United States)
In space plasmas, e.g., planetary magnetospheres and the solar wind, it has been observed that particle velocity distributions typically possess a non-Maxwellian high-energy tail that can be well modeled by a generalized Lorentzian (kappa) distribution. The generalized Lorentzian distribution is characterized by a spectral index k, varies as (energy){sup {minus}(k+1)} at high velocities, and approaches a Maxwellian distribution as k{yields}{infinity}. As a natural analogue to the widely used plasma dispersion function Z({xi}), which is based on the Maxwellian distribution, the authors have recently introduced a new special function Z{sub k}{sup *}({xi}) based on the generalized Lorentzian distribution; they call Z{sub k}{sup *}({xi}) the modified plasma dispersion function. Because Z{sub k}{sup *}({xi}) can be expressed in simple closed form, Z{sub k}{sup *}({xi}) is, moreover, a natural tool for analyzing microinstabilites in a variety of space plasmas. In this paper the authors use Z{sub k}{sup *}({xi}) to analyze three classical problems of plasma physics: Landau damping of Langmuir waves; ion acoustic instability in a current-carrying plasma; and cyclotron resonant instability of electromagnetic R mode waves propagating parallel to an ambient magnetic field. In each case they find that results for a generalized Lorentzian plasma can differ significantly from those in a Maxwellian plasma. Previous calculations based on a Maxwellian distribution, that purport to apply to waves in space, may therefore be subject to reexamination. 30 refs., 4 figs.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 166712
- Journal Information:
- Journal of Geophysical Research, Vol. 97, Issue A11; Other Information: PBD: 1 Nov 1992
- Country of Publication:
- United States
- Language:
- English
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