Current Sheet in a non-Maxwellian collisionless plasma: Self-consistent theory, simulation, and comparison with spacecraft observations

Abstract

A self-consistent theory is constructed of anisotropic current equilibria maintained in a non-Maxwellian plasma consisting of cold electrons and two hot ion components of different temperatures. The ion plasma components are described in the quasi-adiabatic approximation, and the plasma electrons, in the MHD approximation. Approximate steady solutions to the set of Vlasov-Maxwell equations are obtained and investigated parametrically. It is shown that the solutions can describe various current sheet profiles: from thin current structures with a maximum current density in the neutral sheet to comparatively “thick” current sheets with two to three maxima of the current density. It is also shown that the electron plasma component predominates at the current sheet center and can maintain a narrow central peak in the current density. The ion plasma component predominates at the edge of the current sheet, thereby determining the characteristic sheet thickness. The results of numerical simulations of a two-temperature plasma by the macroparticle method are compared with the experimental data from the Cluster spacecraft. Good agreement between the theoretical, numerical, and experimental results leads to the conclusion that the theory developed here provides a fairly adequate description of collisionless current sheets in space plasmas.