Identification and characterization of current sheets in collisionless plasma turbulence

TL;DR

This study uses hybrid-kinetic simulations to analyze current sheets in collisionless plasma turbulence, extending existing algorithms to handle noisier kinetic data and characterizing their key properties.

Contribution

It extends a current sheet analysis algorithm to kinetically turbulent plasmas and verifies its applicability, providing detailed property measurements of current sheets.

Findings

Current sheets thin below ion inertial length scale without electron inertia.

Algorithm successfully analyzes noisier kinetic turbulence data.

Current sheet properties depend on parameter choices like current density thresholds.

Abstract

The properties of current sheets forming in a ion-kinetically turbulent collisionless plasma are investigated by utilizing the results of two-dimensional hybrid-kinetic numerical simulations. For this sake the algorithm proposed by Zhdankin et al. (2013) for the analysis of current sheets forming in MHD-turbulent plasmas, was extended to analyse the role and propertes of current sheets formating in a much noisier kinetically turbulent plasma. The applicability of this approach to the analysis of kinetically-turbulent plasmas is verified. Invesigated are, e.g., the effects of the choice of parameters on the current sheet recognition, viz. the threshold current density, the minimum current density and of the local regions around current density peaks. The main current sheet properties are derived, their peak current density, the peak current carrier velocity (mainly electrons), the thickness and length of the current sheets, i.e. also their aspect ratio (length/thickness). By varying the grid resolution of the simulations it is shown that, as long as the electron inertia is not taken into account, the current sheets thin down well below ion inertial length scale until numerical (grid-resolution based) dissipation stops any the further thinning.