Stability of a finite-β inhomogeneous plasma in a sheared magnetic field

In a plasma immersed in a sheared magnetic field of shear length Ls and having a density gradient of scale length Ln, finite ß (plasma pressure/magnetic pressure) results in an additional stabilizing influence over and above that due to magnetic shear. Employing a full electromagnetic treatment, these finite-ß corrections are evaluated for , where ai is the ion gyration radius and k is the wave vector perpendicular to both the direction of the density gradient and the unsheared component of the magnetic field. For the parameter ranges least stabilized by shear, the dominant finite-ß- stabilization effect occurs within the region about the rational surface where the phase velocity is larger than the Alfvén speed. As ß increases toward or (kaim/M)2/3 [In (MLn/m|Ls|)]4/3 this finite-ß correction must be retained, where m/M = electron mass/ion mass.