Critical Conditions for Drift, Drift-Alfvén and Drift-Tearing Instabilities of Finite-β Plasma in Sheared Magnetic Field

Abstract

Kinetic theory of low frequency instabilities of a current-carrying finite-β plasma in a sheared magnetic field is investigated. Drift mode, drift-Alfven mode and drift-tearing mode are identified both in collisionless and collisional regimes and each critical stability condition is obtained, We find a new electromagnetic localized mode driven by the plasma current in a finite-β plasma. Both the current and finite-β effects are required to excite this mode. It is also shown that, in the absence of the plasma current, any electromagnetic localized mode which is propagating in the direction of the electron diamagnetic drift is stable in the collisionless limit of a finite ion temperature plasma. For the collisional mode, stability holds if ω>ω * (electron diamagnetic frequency) or ω<0.