Collisionless Reconnection in Magnetohydrodynamic and Kinetic Turbulence

TL;DR

This paper extends the theory of reconnection-mediated turbulence to nearly collisionless plasmas, showing that electron inertia drives reconnection and affects the energy spectrum in small-scale turbulence.

Contribution

It introduces a model for reconnection-mediated turbulence in collisionless plasmas, emphasizing electron inertia effects and their impact on turbulence spectra.

Findings

Reconnection-mediated turbulence spectra range from k^{-8/3} to k^{-3}.

Transition scale depends on plasma beta and turbulence model assumptions.

Electron inertia can drive reconnection in collisionless plasma turbulence.

Abstract

It has recently been proposed (Loureiro & Boldyrev 2017; Mallet et al. 2017) that the inertial interval in magnetohydrodynamic (MHD) turbulence is terminated at small scales not by a Kolmogorov-like dissipation region, but rather by a new sub-inertial interval mediated by tearing instability. However, many astrophysical plasmas are nearly collisionless so that the MHD approximation is not applicable to turbulence at small scales. In this Letter, we propose the extension of the theory of reconnection-mediated turbulence to plasmas which are so weakly collisional that the reconnection occurring in the turbulent eddies is caused by electron inertia rather than by resistivity. We find that the transition scale to reconnection-mediated turbulence depends on the plasma beta and on the assumptions of the plasma turbulence model. However, in all cases analyzed, the energy spectra in the reconnection-mediated interval range from $E(k)dk\propto k^{-8/3}dk$ to $E(k)dk\propto k^{-3}dk$.