Drift–Alfven instabilities of a finite beta plasma shear flow along a magnetic field

Abstract

It was derived that the drift–Alfven instabilities with the shear flow parallel to the magnetic field have significant difference from the drift–Alfven instabilities of a shearless plasma when the ion temperature is comparable with electron temperature for a finite plasma beta. The velocity shear not only modifies the frequency and the growth rate of the known drift–Alfven instability, which develops due to the inverse electron Landau damping, but also triggers a combined effect of the velocity shear and the inverse ion Landau damping, which manifests the development of the ion kinetic shear-flow-driven drift–Alfven instability. The excited unstable waves have the phase velocities along the magnetic field comparable with the ion thermal velocity, and the growth rate is comparable with the frequency. The development of this instability may be the efficient mechanism of the ion energization in shear flows.

Drift-Alfven instabilities of a finite beta plasma sheared flow along a magnetic field with inhomogeneous ion temperature

“…( 7) becomes identical to dispersion equation obtained and analysed in Ref. 7 . In this paper, the numerical analysis of Eq.…”

“…It was found in Ref. 7 that the solution to Eq. ( 7) for η i = 0 reveals that the velocity shear is the factor which modifies the dispersion prop-erties of the DA instability which develops 8 in a steady plasma with cold ions (T i T e ) and is the source of the free energy for the development of other DAS instability which is absent in a steady plasma.…”

“…( 7) for η i = 0 reveals that the velocity shear is the factor which modifies the dispersion prop-erties of the DA instability which develops 8 in a steady plasma with cold ions (T i T e ) and is the source of the free energy for the development of other DAS instability which is absent in a steady plasma. It was derived 7 that the left part of line 1 in Fig. 1 (panel (b)), which involves first localised maximum of the growth rate, corresponds to the shear-flow modified DAS instability.…”

“…In parallel shear flows with hot ions, T i T e , the ion kinetic effects play the decisive role in the development the instabilities of the parallel shear flows. In particular, such plasma is prone to the excitation of the shear-flow driving instabilities 6,7 . It was obtained 7 , that in plasma with inhomogeneous density the ion kinetic drift-Alfven (DA) instability develops from the coupled action of the parallel-flow shear and ion Landau damping.…”

“…In particular, such plasma is prone to the excitation of the shear-flow driving instabilities 6,7 . It was obtained 7 , that in plasma with inhomogeneous density the ion kinetic drift-Alfven (DA) instability develops from the coupled action of the parallel-flow shear and ion Landau damping. The growth rate of this instability is of the order of the frequency, the phase velocity of perturbations along the magnetic field is comparable with ion thermal velocity.…”