Storage of magnetic flux at the bottom of the solar convection zone

We consider the mechanical equilibrium of a layer of axisymmetric toroidal magnetic field located in a subadiabatically stratified region near the bottom of the solar convection zone, with particular emphasis on the effects of spherical geometry. We determine equilibrium configurations and simulate numerically how these are reached from a non-equilibrium initial situation. While a subadiabatic stratification is essential for suppressing the buoyancy force, the latitudinal component of the magnetic curvature force is balanced by a latitudinal pressure gradient (in the case of a large subadiabaticity, as in the radiative interior) or by the Coriolis force due to a toroidal flow along the field lines (in the case of small subadiabaticity, as in a layer of convective overshoot). The latter case is found relevant for storing the magnetic flux generated by the solar dynamo. The corresponding equilibrium properties are similar to those of isolated magnetic flux tubes. Significant variations of the differential rotation at the bottom of the convection zone in the course of the solar cycle are expected for such a kind of equilibrium.