A SUBGRID-SCALE RESISTIVITY FOR MAGNETOHYDRODYNAMICS

In this paper an investigation is made of dissipation of small scale m agnetic fields embedded in a turbulent gas flow using magnetohydrodyna mic (MHD) simulations, under conditions suggested by the outer layers of the Sun, where heat is transported by turbulent convection (as esti mated by fluid and magnetic Reynolds numbers), and dissipation is occu rring on small scales. The large eddy simulation approach is utilized along with a model for the unresolved scales. Although a significant a mount of work on modeling the small scales has been done for hydrodyna mic turbulence, the application to MHD has received little attention. This paper specifically deals with the small scale dissipation of magn etic fields and thus a so-called subgrid-scale resistivity is postulat ed and then tested using a series of two-dimensional numerical simulat ions. An attempt is made to clarify the advantages and uncertainties o f using this new formulation of turbulent resistivity in MHD and sugge st areas for improvement and further application.