Hall Magnetohydrodynamics of Reversed Field Current Layers

The dynamics of inhomogeneous, reversed field current layers in the Hall limit (i.e., characteristic length scales ≲ the ion inertial length) are briefly reviewed. We demonstate that a density inhomogeneity along the current direction can dramatically redistribute the magnetic field and plasma via magnetic shock-like or rarefaction waves. The relative direction between the density gradient and current flow plays a critical role in the evolution of the current sheet. Specifically a current sheet can become very thin rapidly when the density gradient is directed opposite to the current. We also show that magnetic reconnection proceeds asymmetrically in a three dimensional system. A localized magnetic field perturbation induces a wave structure that propagates in the direction of the electron drift (i.e., opposite to the current). The propagating wave structure is a Hall phenomenon associated with magnetic field curvature. The interaction between the propagating wave structure and an evolving current layer can lead to rapid magnetic field line reconnection. We apply our results to laboratory and space plasma processes.