Free energy cascade in gyrokinetic turbulence

TL;DR

This paper investigates the transfer of free energy in gyrokinetic turbulence driven by ion temperature gradients, revealing a local, forward cascade similar to fluid turbulence, which informs plasma turbulence understanding and simulation methods.

Contribution

It demonstrates that free energy transfer in gyrokinetic turbulence exhibits properties akin to fluid turbulence, including a local, forward cascade, advancing the understanding of plasma turbulence dynamics.

Findings

Free energy cascades forward from large to small scales.

The cascade is highly local and self-similar.

Results support development of large eddy simulation techniques for gyrokinetics.

Abstract

In gyrokinetic theory, the quadratic nonlinearity is known to play an important role in the dynamics by redistributing (in a conservative fashion) the free energy between the various active scales. In the present study, the free energy transfer is analyzed for the case of ion temperature gradient driven turbulence. It is shown that it shares many properties with the energy transfer in fluid turbulence. In particular, one finds a forward (from large to small scales), extremely local, and self-similar cascade of free energy in the plane perpendicular to the background magnetic field. These findings shed light on some fundamental properties of plasma turbulence, and encourage the development of large eddy simulation techniques for gyrokinetics.