Simultaneous construction of fast equator, poleward meridional flow, and near-surface shear layer in solar magnetohydrodynamic calculation

Abstract

We carry out an unprecedented high-resolution simulation for the solar convection zone. Our calculation reproduces the fast equator and near-surface shear layer (NSSL) of differential rotation and the near-surface poleward meridional flow simultaneously. The NSSL is located in a complex layer where the spatial and time scales of thermal convection are significantly small compared with the deep convection zone. While there have been several attempts to reproduce the NSSL in numerical simulation, the results are still far from reality. In this study, we succeed in reproducing an NSSL in our new calculation. Our analyses lead to a deeper understanding of the construction mechanism of the NSSL, which is summarized as: 1) rotationally unconstrained convection in the near-surface layer transports the angular momentum radially inward; 2) sheared poleward meridional flow around the top boundary is constructed; 3) the shear causes a positive kinetic $\langle v'_r v'_\theta\rangle$ and negative magnetic $\langle B_r B_\theta\rangle$ correlations; and 4) the turbulent viscosity and magnetic tension are latitudinally balanced with the Coriolis force in the NSSL. We emphasize the importance of the magnetic field in the solar convection zone.