3 research outputs found
Small-scale magnetic buoyancy and magnetic pumping effects in a turbulent convection
We determine the nonlinear drift velocities of the mean magnetic field and
nonlinear turbulent magnetic diffusion in a turbulent convection. We show that
the nonlinear drift velocities are caused by the three kinds of the
inhomogeneities, i.e., inhomogeneous turbulence; the nonuniform fluid density
and the nonuniform turbulent heat flux. The inhomogeneous turbulence results in
the well-known turbulent diamagnetic and paramagnetic velocities. The nonlinear
drift velocities of the mean magnetic field cause the small-scale magnetic
buoyancy and magnetic pumping effects in the turbulent convection. These
phenomena are different from the large-scale magnetic buoyancy and magnetic
pumping effects which are due to the effect of the mean magnetic field on the
large-scale density stratified fluid flow. The small-scale magnetic buoyancy
and magnetic pumping can be stronger than these large-scale effects when the
mean magnetic field is smaller than the equipartition field. We discuss the
small-scale magnetic buoyancy and magnetic pumping effects in the context of
the solar and stellar turbulent convection. We demonstrate also that the
nonlinear turbulent magnetic diffusion in the turbulent convection is
anisotropic even for a weak mean magnetic field. In particular, it is enhanced
in the radial direction. The magnetic fluctuations due to the small-scale
dynamo increase the turbulent magnetic diffusion of the toroidal component of
the mean magnetic field, while they do not affect the turbulent magnetic
diffusion of the poloidal field.Comment: 13 pages, 4 figure, REVTEX4, Geophysical and Astrophysical Fluid
Dynamics, in pres