Energy transfer and dual cascade in kinetic magnetized plasma turbulence

TL;DR

This paper develops a theory for the dual cascade in magnetized plasma turbulence, revealing unique behaviors due to gyrokinetic constraints, supported by numerical simulations that enhance understanding of energy transfer across scales.

Contribution

It introduces a novel theoretical framework for the dual cascade in kinetic magnetized plasmas, supported by the first direct numerical observations of these phenomena.

Findings

Identification of a dual cascade distinct from neutral fluid turbulence

Observation of new energy transfer behaviors via gyrokinetic simulations

Framework for understanding local and non-local scale coupling in plasma turbulence

Abstract

The question of how nonlinear interactions redistribute the energy of fluctuations across available degrees of freedom is of fundamental importance in the study of turbulence and transport in magnetized weakly collisional plasmas, ranging from space settings to fusion devices. In this letter, we present a theory for the dual cascade found in such plasmas, which predicts a range of new behavior that distinguishes this cascade from that of neutral fluid turbulence. These phenomena are explained in terms of the constrained nature of spectral transfer in nonlinear gyrokinetics. Accompanying this theory are the first observations of these phenomena, obtained via direct numerical simulations using the gyrokinetic code {\tt AstroGK}. The basic mechanisms that are found provide a framework for understanding the turbulent energy transfer that couples scales both locally and non-locally.