Growth rates of new parametric instabilities occurring in a plasma with streaming He{sup ++}

Journal Article · Thu Dec 01 04:00:00 EST 1994 · Journal of Geophysical Research

DOI:https://doi.org/10.1029/94JA02370· OSTI ID:91324

Jayanti, V; Hollweg, J V ^[1]

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1. Univ. of New Hampshire, Durham, NH (United States)

The authors consider parametric instabilities of a circularly polarized pump Alfven wave, which propagates parallel to the ambient magnetic field; the daughter waves are also parallel-propagating. They follow Hollweg et al. and consider several new instabilities that owe their existence to the presence of streaming alpha particles. One of the new instabilities is similar to the familiar decay instability, but the daughter waves are a forward going alpha sound wave and a backward going Alfven wave. The growth rate of this instability is usually small if the alpha abundance is small. The other three new instabilities occur at high frequencies and small wavelengths. The authors find that the new instability which involves the proton cyclotron wave and alpha sound (i.e., the (+f, {alpha}s) mode) can be the fastest growing instability if {beta} {approx} 1. However, if {beta} is small, then the instability which can compete with the decay instability is the (+f, {minus}{alpha}) instability, which involves both the proton and alpha cyclotron resonances, but the pump wave must have low frequency and large amplitude. These instabilities may be a means of heating and accelerating alpha particles in the solar wind, but this claim is unproven until a fully kinetic study is carried out. 50 refs., 12 figs.

• OSTI ID: 91324
• Journal Information: Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A12 Vol. 99; ISSN JGREA2; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
ALFVEN WAVES
HELIUM IONS
INSTABILITY GROWTH RATES
PARAMETRIC INSTABILITIES
POLARIZATION