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Velocity Shear Instabilities in the Anisotropic Solar Wind

Published online by Cambridge University Press:  04 August 2017

Stefano Migliuolo
Stefano Migliuolo*
Affiliation:
High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80307 USA

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The linear and quasilinear theory of perturbations in finite-β (β is the ratio of plasma pressure to magnetic energy density), collisionless plasmas, that have sheared (velocity) flows, is developed. A simple, one-dimensional magnetic field geometry is assumed to adequately represent solar wind conditions near the sun (i.e., at R ≃ 0.3 AU). Two modes are examined in detail: an ion-acoustic mode (finite-β stabilized) and a compressional Alfven mode (finite-β threshold, high-β stabilization). The role played by equilibrium temperature anisotropies, in the linear stability of these modes, is also presented. From the quasilinear theory, two results are obtained. First, the feedback of these waves on the state of the wind is such as to heat (cool) the ions in the direction perpendicular (parallel) to the equilibrium magnetic field. The opposite effect is found for the electrons. This is in qualitative agreement with the observed anisotropies of ions and electrons, in fast solar wind streams. Second, these quasilinear temperature changes are shown to result in a quasilinear growth rate that is lower than the linear growth rate, suggesting saturation of these instabilities.

Type
Session V
Information
Symposium - International Astronomical Union , Volume 107: Unstable Current Systems and Plasma Instabilities , 1985 , pp. 371 - 374
Copyright
Copyright © Reidel 1985 

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