Speaker
Piyali Chatterjee
Description
A strong toroidal field can exist in form of a magnetic
layer in the overshoot region below the solar convection
zone. This motivates a more detailed study of the magnetic
buoyancy instability with rotation. We calculate the alpha
effect due to helical motions caused by a disintegrating
magnetic layer in a rotating density-stratified system with
angular velocity Omega making an angle theta with the
vertical. We also study the dependence of the alpha effect
on theta and the strength of the initial magnetic field. We
carry out three-dimensional hydromagnetic simulations in
Cartesian geometry. A turbulent EMF due to the correlations
of the small scale velocity and magnetic field is generated.
We use the test-field method to calculate the transport
coefficients of the inhomogeneous turbulence produced by the
layer. We show that the growth rate of the instability and
the twist of the magnetic field vary monotonically with the
ratio of thermal conductivity to magnetic diffusivity. The
resulting alpha effect is inhomogeneous and increases with
the strength of the initial magnetic field. It is thus an
example of an "anti-quenched" alpha effect. The alpha effect
is nonlocal, requiring around 8--16 Fourier modes to
reconstruct the actual EMF based on the actual mean field.
