The dynamo layer in solar-type stars

The role of the dynamo layer for dynamo action in solar-type stars is discussed. As a result of instabilities, magnetic flux is expelled from the dynamo layer into the convection zone above it. The resulting partial evacuation of the dynamo layer and amplification of the deep-seated toroidal magnetic field is investigated in an illustrative 3D numerical simulation. The simulation is performed with a finite-difference code that solves the anelastic MHD equations for a Cartesian geometry. It is found that the field strength in the dynamo layer is amplified by a factor of up to about 7.