GAFD Seminar: Conan Liptrott (University of Warwick)

Magnetohydrodynamic (MHD) turbulence exhibits a turbulent cascade similar to neutral fluid turbulence. The role of 'coherent structures' in this cascade is widely debated, in part due to the additional physics associated with a conducting fluid. The traditional approach is to find statistical correlations between measures of energy transfer and measures of field structure. In a recent work [1], we have provided the first analytic connection between energy transfer and coherent structures in MHD turbulence (to the authors' knowledge). We perform a scale-by-scale analysis of energy flux in the turbulent cascade using the spatially filtered MHD equations and characterise the structure of velocity and magnetic fields using the gradient tensor invariants. By combining these approaches, we bound the maximum possible energy transfer explicitly in terms of field structure. We also present a semi-empirical framework for predicting the energy flux locally. I will discuss connections to Navier-Stokes fluid turbulence, which is contained in this analysis as a sub-problem. 

[1] Liptrott et al., "Tensor invariant approach to energy flux in magnetohydrodynamic turbulence", Phys. Rev. E (2026) DOI: 10.1103/xxy9-xhts