Propinquity of current and vortex structures: effects on collisionless plasma heating

TL;DR

This paper investigates how vorticity and current structures influence collisionless plasma heating, revealing that vorticity plays a more significant role than current sheets in energization and thermal anisotropy.

Contribution

It demonstrates through kinetic simulations that vorticity enhances local plasma heating and affects proton thermal properties, extending understanding of plasma turbulence effects.

Findings

Vorticity correlates strongly with plasma heating.

Vorticity influences proton thermal anisotropy.

Heating effects are sign-dependent on vorticity.

Abstract

Intermittency of heating in weakly collisional plasma turbulence is an active subject of research, with significant potential impact on understanding of the solar wind, solar corona and astrophysical plasmas. Recent studies suggest a role of vorticity in plasma heating. In magnetohydrodynamics small scale vorticity is generated near current sheets and this effect persists in kinetic plasma, as demonstrated here with hybrid and fully kinetic Particle-In-Cell (PIC) simulations. Furthermore, vorticity enhances local kinetic effects, with a generalized resonance condition selecting sign-dependent enhancements or reductions of proton heating and thermal anisotropy. In such plasmas heating is correlated with vorticity and current density, but more strongly with vorticity. These results help explain several prior results that find kinetic effects and energization near to, but not centered on, current sheets. Evidently intermittency in kinetic plasma involves multiple physical quantities, and the associated coherent structures and nonthermal effects are closely related.