Solar-like differential rotation in a convective dynamo with a coronal envelope
by
J(Nordita & Astronomy Department), ouml;rn Warnecke(Nordita & Astronomy Department)
→
Europe/Stockholm
122:026
122:026
Description
.We report on the results of three convective dynamo simulations with an
outer coronal layer.
The magnetic field is self-consistently generated by the convective
motions beneath the surface.
Above the convection zone we include a polytropic layer
that extends to 1.6 solar radii.
The temperature increases in this region
to ~8 times the value at the surface, corresponding to
~1.2 times the value at the bottom of the spherical shell.
We associate this region with the solar corona.
We find a solar-like differential rotation with radial contours of
constant rotation rate, together with a solar-like meridional
circulation and a near-surface shear layer.
This spoke-like rotation profile is caused by a non-zero latitudinal
entropy gradient which violates the Taylor-Proudman balance via the
baroclinic term.
The lower density stratification compared with the Sun leads to an
equatorward return flow above the surface.
The mean magnetic field is in most of the cases
oscillatory with equatorward migration in one case.
In other cases the equatorward migration is overlaid by stationary or
even poleward migrating mean fields.
