Shear-current effect in a turbulent convection with a large-scale shear.
The shear-current effect in a nonrotating homogeneous turbulent convection with a large-scale constant shear is studied. The large-scale velocity shear causes anisotropy of turbulent convection, which produces the mean electromotive force epsilon (W) proportional to W x J and the mean electric current along the original mean magnetic field, where W is the background mean vorticity due to the shear and J is the mean electric current. This results in a large-scale dynamo even in a nonrotating and nonhelical homogeneous sheared turbulent convection, whereby the alpha effect vanishes. It is found that turbulent convection promotes the shear-current dynamo instability, i.e., the heat flux causes positive contribution to the shear-current effect. However, there is no dynamo action due to the shear-current effect for small hydrodynamic and magnetic Reynolds numbers even in a turbulent convection, if the spatial scaling for the turbulent correlation time is tau(k) proportionalto to k-2, where k is the small-scale wave number.
Rogachevskii
Igor
I
Department of Mechanical Engineering, The Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105, Israel. gary@bgu.ac.il
Kleeorin
Nathan
N