3D MHD Modeling of the Impact of Subsurface Stratification on the Solar Dynamo

Various models of solar subsurface stratification are tested in the global EULAG-MHD solver to simulate diverse regimes of near-surface convective transport. Sub- A nd superadiabacity are altered at the surface of the model (r > 0.95R _o) to either suppress or enhance convective flow speeds in an effort to investigate the impact of the near-surface layer on global dynamics. A major consequence of increasing surface convection rates appears to be a significant alteration of the distribution of angular momentum, especially below the tachocline where the rotational frequency predominantly increases at higher latitudes. These hydrodynamic changes correspond to large shifts in the development of the current helicity in this stable layer (r < 0.72R _o), significantly altering its impact on the generation of poloidal and toroidal fields at the tachocline and below, acting as a major contributor toward transitions in the dynamo cycle. The enhanced near-surface flow speed manifests in a global shift of the toroidal field (B _φ) in the butterfly diagram, from a north-south symmetric pattern to a staggered antisymmetric emergence.