MPS Seminar: Turbulent helicity and the effective momentum transport (N. Yokoi)

Helicity density (hereafter helicity), representing local structural properties of turbulence, is known to play important roles in the global magnetic-field induction (dynamos). In this talk, special emphasis is put on the role of helicity in the momentum transport. In addition to the usual eddy viscosity (represented by the turbulent energy), in the presence of breaking symmetry, a finite turbulent helicity effect enters the Reynolds stress. Recent developments on this line of studies are reported, which include the analysis of the stress equation, subgrid-scale (SGS) modelling. A possible application of this effect to the angular-momentum transport in the solar convection zone, as well as the extension to the magnetohydrodynamic (MHD) case, will be discussed.