Velocity shear driven electron skin size vortices

Abstract

Nonlinear electromagnetic perturbations in a nonuniform plasma are studied in the presence of nonuniform flows that are aligned either perpendicular or parallel to the ambient magnetic field lines. Coherent structures with typical spatial scales of the order of the electron skin depth are found in the form of a stationary tripolar vortex, and for spatial scales of the order of the electron Larmor radius at the ion temperature in the form of a vortex chain. In both cases, the structures are driven and carried by the plasma flow. In the case of a parallel flow, the dipolar vortex propagates perpendicular to the field lines. For plasma in the Earth’s magnetotail, the solutions presented here should be expected at spatial scales of the order of about 10–20 km.