Multilayered solar interface dynamos: from aCartesian kinematic dynamo to a sphericaldynamic dynamo

摘要

The existence of the solar tachocline, a thin differentially rotating layer at the base of theconvection zone which is inferred from helioseismology, leads to the concept of an interfacedynamo. The tachocline is magnetically coupled to the radiative interior and the overlyingconvection zone. A multilayered interface dynamo is required to describe the dynamo processinvolved. We first discuss a two-dimensional multilayered interface dynamo model in cartesiangeometry consisting of four horizontal layers with different magnetic diffusivities magneticallycoupled by the three sets of interface matching conditions for the generated magnetic field.Exact solutions of the coupled dynamo system are obtained in this model. We then discussa fully three-dimensional and multi-layered spherical dynamic interface dynamo using a finiteelement method based on the three-dimensional tetrahedralization of the whole spherical system.The spherical dynamic interface dynamo also consists of four magnetically coupled zones. In theconvection zone, the fully three-dimensional dynamic feedback of Lorentz forces is taken intoaccount. It is shown that the dynamo is characterized by a strong toroidal magnetic field, selectsdipolar symmetry and propagates equatorward.