Hall MHD reconnection in cometary magnetotail

Abstract

The fine structure of cometary tails (swirls, loops and blobs) is studied in the framework of resistive magnetic reconnection without a guide field in a dusty plasma. For a high‐beta plasma (β ∼ 1) consisting of electrons, ions, and immobile dust grains, a two‐fluid description is used to study electromagnetic perturbations with the frequency below Ωi, propagating at an arbitrary angle, and including the effects of Hall current. A zero‐order current associated with the anti‐parallel magnetic configuration may exist even in the limit of zero plasma temperature in a dusty plasma due to a symmetry breaking between electrons and ions by dust grains that yields an E × B current. In the perturbed state, a new linear electromagnetic mode is found in dusty plasma which is evanescent below the Rao cut‐off frequency and has the characteristic wavelength comparable to the ion skin depth, which enables the reconnection at short spatial scales. The role of the dust is found to be twofold, yielding a new mode outside...