Inertial Kinetic-Alfv\'en Turbulence

TL;DR

This paper confirms through kinetic simulations that inertial kinetic-Alfvén turbulence exists in low electron beta plasma environments, showing a transition at electron inertial scales and aligning with theoretical predictions and observational data.

Contribution

The study provides the first numerical confirmation of inertial kinetic-Alfvén turbulence and characterizes its spectral properties and transition scales.

Findings

Existence of inertial kinetic-Alfvén turbulence confirmed by simulations

Spectral slopes at sub-electron inertial scales match theoretical predictions

Results consistent with observations in Earth's magnetosheath

Abstract

Recent observational and analytical studies suggested that a new regime of kinetic turbulence may exist in plasma environments with low electron beta (Chen and Boldyrev, 2017). Such a regime, termed inertial kinetic-Alfv\'en turbulence, is relevant for the solar corona, Earth's magnetosheath, and other astrophysical systems where the electron and ion plasma beta parameters satisfy the condition $\beta_e\ll \beta_i\lesssim 1$. In this paper we present kinetic numerical simulations that confirm existence of the iKAW regime. Specifically, the simulations demonstrate a transition at scales below electron inertial length $d_e$ when $\beta_e\ll \beta_i\lesssim 1$. Spectral slopes and other statistical properties of turbulence at sub-$d_e$ scales are consistent with the phenomenological theory of inertial kinetic-Alfv\'en turbulence proposed by Chen and Boldyrev (2017) and with the recent observations in the Earth's magnetosheath.