Helioseismic Constraints on the Solar Interior Dynamics and Dynamo

Abstract:

Uninterrupted helioseismic observations from the SoHO/MDI, SDO/HMI and GONG instruments for more than two decades provide unique observational data for studying the solar-cycle variations of the differential rotation, large-scale and meridional flows. The data also allows us to investigate changes in the thermodynamic structure associated with dynamo-generated magnetic fields. The wealth of global and local helioseismic data provides theoretical constraints on the solar dynamics and dynamo models. The synergy of helioseismic inferences with advanced MHD modeling sheds light on the origin of the solar activity cycles. It helps to understand better the physical processes that control the strength and duration of the cyclic magnetic activity and leads to new physics-based approaches for prediction of the solar cycles. We briefly overview the current status, discuss the solar dynamical structure and evolution revealed by helioseismic inversions and the forward-modeling method, and focus on the most critical points of the problem. In particular, we discuss recent advances in measurements and modeling of the solar-cycle variations of the meridional circulation and migrating zonal flows (torsional oscillations) on the solar surface and in the subsurface layers, the deep convection zone, and the solar tachocline. The relationships between the internal dynamics and the evolution of global magnetic fields lead to new ideas of how magnetic fields are generated and affect the solar flows and structure.