Effect of Magnetic Curvature on Density Gradient Drift Instabilities

Abstract

The effect of magnetic curvature on density gradient drift instabilities is examined for a collisionless plasma in which β stratifies m⁄M<β<<1, where β=plasma pressure/magnetic pressure, m and M are the electron and ion masses respectively. For simplicity, the effect of magnetic curvature is simulated by an equivalent gravitational field. The present considerations are restricted to the cases where the wavelength of perturbations is much longer than the mean ion Larmor radius and the radius of magnetic curvature is much larger than the characteristic length of the density gradient. It is found that the slow Alfvén mode which is unstable in a straight and parallel magnetic field stabilized by magnetic curvature with a sign favorable to stabilization of the interchange instability while it remains unstable by unfavorable curvature, and that the fast Alfvén mode remains stable independently of the sign of magnetic curvature.