von K\'arm\'an energy decay and heating of protons and electrons in a kinetic turbulent plasma

TL;DR

This paper investigates the decay of kinetic plasma turbulence using particle-in-cell simulations, revealing how energy dissipation and particle heating depend on turbulence amplitude, with implications for solar wind and corona conditions.

Contribution

It demonstrates that energy decay in kinetic plasma turbulence follows a von Kármán similarity hypothesis and shows how electron and proton heating vary with turbulence amplitude.

Findings

Energy decay aligns with von Kármán similarity decay.

Electrons are preferentially heated at low turbulence amplitudes.

Protons dominate heating at higher turbulence amplitudes.

Abstract

Decay in time of undriven weakly collisional kinetic plasma turbulence in systems large compared to the ion kinetic scales is investigated using fully electromagnetic particle-in-cell simulations initiated with transverse flow and magnetic disturbances, constant density, and a strong guide field. The observed energy decay is consistent with the von K\'arm\'an hypothesis of similarity decay, in a formulation adapted to magnetohydrodyamics (MHD). Kinetic dissipation occurs at small scales, but the overall rate is apparently controlled by large scale dynamics. At small turbulence amplitude the electrons are preferentially heated. At larger amplitudes proton heating is the dominant effect. In the solar wind and corona the protons are typically hotter, suggesting that these natural systems are in large amplitude turbulence regime.