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Electromagnetic instabilities of low-beta alpha/proton beams in space plasmas

Journal Contribution - Journal Article

Relative drifts between di erent species or particle populations are characteristic to solar plasma out ows, e.g., in the fast streams of the solar winds, coronal mass ejections and interplanetary shocks. This paper characterizes the dispersion and stability of the low-beta alpha/proton drifts in the absence of any in- trinsic thermal anisotropies, which are usually invoked in order to stimulate various instabilities. The disper- sion relations derived here describe the full spectrum of instabilities and their variations with the angle of propagation and plasma parameters. The results un- veil a potential competition between instabilities of the electromagnetic proton cyclotron and alpha cyclotron modes. For conditions speci c to a low-beta solar wind, e.g., at low heliocentric distances in the outer corona, the instability operates on the alpha cyclotron branch. The growth rates of the alpha cyclotron mode are sys- tematically stimulated by the (parallel) plasma beta and/or the alpha-proton temperature ratio. One can therefore expect that this instability develops even in the absence of temperature anisotropies, with poten- tial to contribute to a self-consistent regulation of the observed drift of alpha particles.
Journal: Astrophysics and Space Science
ISSN: 0004-640X
Issue: 6
Volume: 365
Publication year:2020
BOF-keylabel:yes
IOF-keylabel:yes
BOF-publication weight:1
CSS-citation score:1
Authors:International
Authors from:Higher Education
Accessibility:Open