Proton and helium cyclotron anisotropy instability thresholds in the magnetosheath

Journal Article · Fri Apr 01 04:00:00 EST 1994 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/93JA03243· OSTI ID:121232

Gary, S P; Convery, P D ^[1]; Denton, R E ^[2]; Fuselier, S A ^[3]; Anderson, B J ^[4]

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1. Los Alamos National Lab., NM (United States)
2. Dartmouth College, Hanover, NH (United States)
3. Lockheed Palo Alto Research Lab., CA (United States)
4. Johns Hopkins Univ., Laurel, MD (United States)

Both the protons and the helium ions of the terrestrial magnetosheath typically display T{sub {perpendicular}} > T{sub {parallel}}, where {perpendicular} and {parallel} denote directions perpendicular and parallel to the background magnetic field. Observations of the highly compressed magnetosheath show an inverse correlation between these ion temperature anisotropies and the parallel proton {beta}. Computer simulations have demonstrated that these correlations are due to wave-particle scattering by electromagnetic ion cyclotron anisotropy instabilities. These correlations correspond to linear theory thresholds of the proton cyclotron and the helium cyclotron instabilities. This paper uses linear Vlasov theory and the assumption of a constant maximum growth rate to obtain closed-form expressions for these thresholds as a function of the relative helium density and the parallel proton {beta} in a parameter model of the magnetosheath. 22 refs., 6 figs., 1 tab.

• OSTI ID: 121232
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A4 Vol. 99; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ANISOTROPY
BETA RATIO
BOLTZMANN-VLASOV EQUATION
CYCLOTRON RESONANCE
HELIUM IONS
ION TEMPERATURE
MAGNETOSHEATH
PLASMA INSTABILITY
PROTONS