Gyrokinetic Simulations of Solar Wind Turbulence from Ion to Electron Scales

TL;DR

This paper presents the first 3D gyrokinetic simulation of solar wind turbulence from ion to electron scales, showing consistency with spacecraft observations and revealing ion heating and the entropy cascade.

Contribution

It introduces a realistic, nonlinear gyrokinetic simulation resolving scales from ion to electron gyroradius with physical damping mechanisms.

Findings

Energy spectrum scaling of approximately k^{-2.8} matches observations.

Linear kinetic Alfvén wave mode describes turbulence polarization.

First evidence of ion entropy cascade in electromagnetic turbulence simulation.

Abstract

The first three-dimensional, nonlinear gyrokinetic simulation of plasma turbulence resolving scales from the ion to electron gyroradius with a realistic mass ratio is presented, where all damping is provided by resolved physical mechanisms. The resulting energy spectra are quantitatively consistent with a magnetic power spectrum scaling of $k^{-2.8}$ as observed in \emph{in situ} spacecraft measurements of the "dissipation range" of solar wind turbulence. Despite the strongly nonlinear nature of the turbulence, the linear kinetic \Alfven wave mode quantitatively describes the polarization of the turbulent fluctuations. The collisional ion heating is measured at sub-ion-Larmor radius scales, which provides the first evidence of the ion entropy cascade in an electromagnetic turbulence simulation.