Sensitivity of a Babcock-Leighton Flux-Transport Dynamo to Magnetic Diffusivity Profiles

Abstract. We study the influence of various magnetic diffusivity profiles on the evo-lution of the poloidal and toroidal magnetic fields in a flux transport dynamo model for the Sun. The diffusivity is a poorly understood ingredient in kinematic, flux-transport dynamo models. We mathematically construct various theoretical profiles of the depth-dependent diffusivity, based on constraints from mixing length theory and turbulence, and on comparisons of poloidal field evolution on the Sun with that from the flux-transport dynamo model. We then study the effect of each profile in the cyclic evolution of the dynamo fields in the Sun, by solving the mean-field dynamo equations. Deriving the theoretical time-latitude diagrams from model output, we discuss how they compare with solar synoptic maps. We also investigate how the toroidal and poloidal field structures inside the convection zone are influenced by different diffusivity profiles. We conduct three experiments: (I) comparing very different profiles; (II) comparing different locations of diffusivity gradient near the tachocline for the optimal profile; and (III) comparing different slopes of diffusivity gradient for the optimal profile. Based on these simulations, we comment on which aspects of depth-dependent dif-fusivity profiles may be most relevant for magnetic flux evolution in the Sun, and how certain observations could help improve knowledge of this dynamo ingredient