3He enrichments by magnetosonic waves in current-driven instabilities

Details 3He enrichments by magnetosonic waves in current-driven instabilities 3He enrichments by magnetosonic waves in current-driven instabilities

Apr 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995soph..158..115z&link_type=abstract

Solar Physics, Volume 158, Issue 1, pp.115-137

Physics

14

Scientific paper

A theoretical model for3He enrichments in solar energetic particles is developed. First, current-driven, electrostatic instabilities that have frequenciesω ≈ nΩ 3_{He} (Ω 3_{He} is the cyclotron frequency of3He) are investigated for a plasma consisting of H,4He,3He, and electrons with the density of3He much lower than those of H and4He. It is found that in many cases the oblique ion-acoustic waves can have positive growth rates at frequenciesω ≈ Ω 3_{He} and, at the same time, negative growth rates atω ≈ Ω 4_{He} and atω ≈ ΩH. This can occur near the marginal state of the instability. The wave damping at these frequencies is caused by the cyclotron resonances of4He and H. The cyclotron damping atω ≈ Ω 3_{He} is negligible, however, because the abundance of3He is very small. The H cyclotron waves can be unstable atω ≈ 2Ω 3_{He} for a wide region of plasma parameters; the electron-to-ion temperature ratio must beT e /T H ≳ 1.5. To destabilize the4He cyclotron waves withω ≈ Ω 3_{He} , high4He density and high electron temperature are both required. Then,3He enrichments are studied on the basis of the theory of nonlinear magnetosonic waves, which can promptly accelerate ions. The current-driven electrostatic waves withω ≈ nΩ 3_{He} can enhance fluctuation velocities of3He. Thus, in the presence of these waves, magnetosonic waves can selectively accelerate3He particles to high energies. Finally, cyclotron resonances of heavy ions with the wavesω ≈ nΩ 3_{He} orω< Ω 4_{He} are briefly discussed.

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