Kinetic Simulations of Magnetized Turbulence in Astrophysical Plasmas

TL;DR

This paper reports the first fully electromagnetic kinetic simulations of magnetized turbulence at the ion gyroscale, revealing spectral breaks and slopes consistent with theoretical predictions and solar wind observations.

Contribution

It provides the first ab initio kinetic simulation results of magnetized turbulence at the ion gyroscale, bridging theory and solar wind measurements.

Findings

Spectral break at the ion gyroscale observed.

Spectral slopes match critical balance turbulence predictions.

Turbulent fluctuation frequencies stay below the ion cyclotron frequency.

Abstract

This letter presents the first ab initio, fully electromagnetic, kinetic simulations of magnetized turbulence in a homogeneous, weakly collisional plasma at the scale of the ion Larmor radius (ion gyroscale). Magnetic and electric-field energy spectra show a break at the ion gyroscale; the spectral slopes are consistent with scaling predictions for critically balanced turbulence of Alfven waves above the ion gyroscale (spectral index -5/3) and of kinetic Alfven waves below the ion gyroscale (spectral indices of -7/3 for magnetic and -1/3 for electric fluctuations). This behavior is also qualitatively consistent with in situ measurements of turbulence in the solar wind. Our findings support the hypothesis that the frequencies of turbulent fluctuations in the solar wind remain well below the ion cyclotron frequency both above and below the ion gyroscale.