Fully Kinetic Simulation of 3D Kinetic Alfven Turbulence

TL;DR

This study uses 3D particle-in-cell simulations to explore kinetic Alfvén turbulence at solar wind scales, confirming theoretical predictions and showing a critically balanced cascade consistent with observations.

Contribution

It provides the first-principles simulation evidence that kinetic Alfvén turbulence exhibits a critically balanced cascade, aligning with solar wind measurements.

Findings

Spectral properties match kinetic Alfvén wave theory.

Subion range anisotropy is scale-dependent with $k_{\parallel}<k_{\perp}$.

The kinetic cascade approaches critical balance with linear and nonlinear timescales comparable.

Abstract

We present results from a three-dimensional particle-in-cell simulation of plasma turbulence, resembling the plasma conditions found at kinetic scales of the solar wind. The spectral properties of the turbulence in the subion range are consistent with theoretical expectations for kinetic Alfv\' en waves. Furthermore, we calculate the local anisotropy, defined by the relation $k_{\parallel}(k_{\perp})$, where $k_{\parallel}$ is a characteristic wave number along the local mean magnetic field at perpendicular scale $l_{\perp}\sim 1/k_{\perp}$. The subion range anisotropy is scale dependent with $k_{\parallel}<k_{\perp}$ and the ratio of linear to nonlinear time scales is of order unity, suggesting that the kinetic cascade is close to a state of critical balance. Our results compare favorably against a number of \emph{in situ} solar wind observations and demonstrate---from first principles---the feasibility of plasma turbulence models based on a critically balanced cascade of kinetic Alfv\' en waves.