Locality properties of the free energy fluxes in gyrokinetic turbulence

TL;DR

This study investigates the nonlinear interactions and energy transfer locality in gyrokinetic turbulence driven by ion-temperature gradients using numerical simulations, revealing non-local IR interactions despite local energy cascades.

Contribution

It provides a detailed analysis of the locality properties of free energy fluxes in gyrokinetic turbulence, highlighting non-local IR interactions and the absence of a universal locality regime.

Findings

Non-local infrared interactions dominate in gyrokinetic turbulence.

A local energy cascade is observed despite non-local IR behavior.

No asymptotic universal locality exponents are found due to dissipation.

Abstract

The nature of the nonlinear interactions in gyrokinetic (GK) turbulence, driven by an ion-temperature gradient instability, is investigated using numerical simulations of single ion species plasma in three-dimensional flux tube geometry. To account for the level of separation existing between scales involved in an energetic interaction, the degree of locality of the free energy scale flux is analyzed employing Kraichnan's infrared (IR) and ultraviolet locality functions. Due to the nontrivial dissipative nature of GK turbulence, an asymptotic level for the locality exponents, indicative of a universal dynamical regime for GK's, is not recovered and an accentuated non-local behavior of the IR interactions is found instead, in spite of the local energy cascade observed.