Investigation of model micro-scale reconnecting plasma modes

Abstract

We numerically and analytically investigate the linear complex mode frequencies of model micro-reconnecting plasma modes which have transverse wavelengths of the order of the electron skin depth c/lwpe. This model mode, which can have finite wavelength parallel to the magnetic field, is found in the limit of a straight and uniform magnetic field in the presence of temperature gradients. The theory of the related micro-reconnecting modes has been previously developed in view of explaining the observation of macroscopic instabilities which are not predicted by the drift tearing mode theory [2]. These micro-reconnecting modes are radially localized by magnetic shear and lead to the formation of microscopic magnetic islands. We derive the model dispersion equation, which closely follows the derivation of the micro-reconnecting mode dispersion equation [1], under relevant conditions using the drift kinetic approximation. We also consider the dispersion relation in the fluid limit [1]. We examine the solutions of the resulting dispersion relations and confirm the driving effect of the electron temperature gradient, and the stabilizing effect of a density gradient.