Constraints on the Applicability of an Interface Dynamo to the Sun

Abstract

Taking into account the helioseismically inferred interior structure, we show that a pure interface-type dynamo does not work for the Sun if the skin effect for poloidal fields does not allow them to penetrate the tachocline. Using a simple mean-field kinematic α-Ω dynamo model, we demonstrate that, in the absence of tachocline radial shear participating in the dynamo process, a latitudinal differential rotation can provide the necessary Ω-effect to drive an oscillation in an interface dynamo, but it alone cannot produce the latitudinal migration. We show that to make an interface dynamo work with the constraints of interior structure and skin depth, a meridional circulation is essential. We conclude that a flux-transport dynamo driven by both the Babcock-Leighton and interface/bottom α-effects is a robust large-scale dynamo for the Sun.