Enhancement of wave growth for warm plasma with a high-energy tail distributions

Journal Article · Tue Jan 01 04:00:00 EST 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/90JA01629· OSTI ID:5313169

Thorne, R M ^[1]; Summers, D ^[2]

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1. Univ. of California, Los Angeles (USA)
2. Memorial Univ. of Newfoundland, St. John's (Canada)

The authors consider the classical linear theory of electromagnetic wave growth in a warm plasma for waves propagating parallel to a uniform ambient magnetic field. Wave growth rates {gamma} are calculated for ion-driven right-hand mode waves for Kappa (bi-Lorentzian) and Maxwellian particle distribution functions. Systematic calculations of {gamma} are carried out for various values of the spectral index {kappa}, the temperature anisotropy A{sup +} = 1 {minus} (T{sub {perpendicular}}{sup +}/T{sub {parallel}}{sup +}), and the ration {beta}{sup +} of plasma pressure to magnetic pressure, appropriate to the solar wind. When the anisotropy is low (A{sup +} {much lt} 1), the wave growth is limited to frequencies below the proton gyrofrequency., and the growth rate increases dramatically as the spectral index {kappa} is reduced (i.e., as the high-energy tail becomes more pronounced). The growth rate for any Kappa distribution greatly exceeds (often by several orders of magnitude) that for a Maxwellian with the same bulk properties. For large thermal anisotropy (T{sub {parallel}}{sup +} {much gt} T{sub {perpendicular}}{sup +}) the growth rate from either distribution is greatly enhanced. In comparison to a Maxwellian distribution the growth rates from a Kappa distribution are generally larger, and significant wave growth occurs over a broader range of frequencies. Evidently, the theory is important in the study of microinstabilities in space plasmas in which a high-energy tail distribution is generally present.

• OSTI ID: 5313169
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A1; ISSN JGREA; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

640104 -- Astrophysics & Cosmology-- Solar Phenomena
640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
DISTRIBUTION FUNCTIONS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
FUNCTIONS
INSTABILITY
INSTABILITY GROWTH RATES
MAGNETIC FIELDS
PLASMA
PLASMA DENSITY
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
PLASMA PRESSURE
PLASMA WAVES
SOLAR ACTIVITY
SOLAR WIND
WAVE PROPAGATION