The role of field correlations on turbulent dissipation

Abstract

Nonlinear phenomena and turbulence are central to our under- standing 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 unex- pected 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 scal- ing laws, together with data analysis from existing experiments, observations and numerical simulations. Finally, I will also briefly explore the possible im- plications for validity and use of several modeling strategies.