Electromagnetic ion-cyclotron instability in space plasmas

Journal Article · Fri Oct 01 04:00:00 EDT 1993 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/93JA00790· OSTI ID:75632

Xue, S; Thorne, R M ^[1]; Summers, D ^[2]

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1. Univ. of California, Los Angeles, CA (United States)
2. Memorial Univ. of Newfoundland, St. John`s, Newfoundland (Canada)

Natural space plasmas generally exhibit a pronounced high-energy tail distribution that can best be modeled by a generalized Lorentzian (kappa) distribution. The authors employ the recently introduced modified plasma dispersion function to obtain the dispersion relation for field-aligned electromagnetic waves in such a plasma, and use this to study the instability properties of R mode and L mode waves in the solar wind and in planetary magnetospheres. They demonstrate for a wide range of plasma parameters that the growth of R mode waves in the solar wind can be significantly enhanced by the presence of a pronounced high-energy tail; previous studies based on a Maxwellian distribution could therefore be seriously in error. The corresponding enhancement in the growth rate of L mode waves in planetary magnetospheres is less dramatic, but the kappa distribution tends to produce significant wave amplification over a broader range of frequency than a Maxwellian distribution with comparable bulk properties. At frequencies comparable to the ion gyrofrequency wave growth is primarily caused by cyclotron resonance with ions. Hot anisotropic electrons can nevertheless influence the instability as a result of changes in the wave phase velocity. This modulating effect is most important for a Maxwellian plasma and becomes less significant as the spectral index of the kappa distribution is reduced. 15 refs., 11 figs.

• Sponsoring Organization: USDOE
• OSTI ID: 75632
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A10 Vol. 98; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CYCLOTRON INSTABILITY
ELECTROMAGNETIC RADIATION
PLASMA
PLASMA WAVES
SOLAR WIND
TAIL IONS