The role of field correlations on turbulent dissipation

TL;DR

This paper investigates how field correlations influence turbulent dissipation in fluids and plasmas, using exact laws, data analysis, and scaling laws to understand intermittency and dissipation mechanisms.

Contribution

It introduces a method to measure dissipation and intermittency in turbulent plasmas through cross-correlation tensors based on invariance principles.

Findings

Identification of non-Gaussian wings in large-scale fields

Evidence of double constant-flux cascades in turbulence

Scaling laws linking field correlations to dissipation

Abstract

Nonlinear phenomena and turbulence are central to our understanding and modeling the dynamics of fluids and plasmas, and yet they still resist analytical resolutions in many instances. However, progress has been made recently, displaying a richness of phenomena which was somewhat unexpected a few years back, such as the double constant-flux cascades of a same invariant to both the large and to the small scales, or the presence of non-Gaussian wings in the large-scale fields, for fluids and plasmas. Here, I will concentrate on the direct measurement of the magnitude of dissipation and an evaluation of intermittency in a turbulent plasma using exact laws stemming from invariance principles and involving cross-correlation tensors with both the velocity and the magnetic fields. I will illustrate these points through scaling laws, together with data analysis from existing experiments, observations and numerical simulations. Finally, I will also briefly explore the possible implications for validity and use of several modeling strategies. To appear, Plasma Physics and Controlled Fusion, 2023.