3D Radiative Hydrodynamic Modeling of the Near-Surface Shear Layer in the Solar Convection Zone

Abstract

Understanding effects driven by rotation in the solar convection zone is essential for many problems related to solar activity, such as the formation of differential rotation, meridional circulation, and others. We present realistic 3D radiative hydrodynamics simulations of solar subsurface dynamics in the presence of rotation in a local domain 80 Mm-wide and 25 Mm deep, located at 30 degrees latitude. The simulation results reveal the development of a shallow 10-Mm deep near-surface shear layer ("leptocline"), characterized by a strong radial rotational gradient and self-organized meridional flows. This shear layer is located in the hydrogen ionization zone associated with enhanced anisotropic convective flows overshooting into a relatively stable zone between the H and HeII ionization zones. The radial variations of the differential rotation and meridional circulation profiles obtained from the simulations agree with helioseismic observations, indicating that a major role in forming the leptocline and subsurface meridional flows is played by the local Reynolds stresses.

Implicit Large-eddy Simulations of Global Solar Convection: Effects of Numerical Resolution in Nonrotating and Rotating Cases

“…Concurrently, the fast convective motions in this layer are not constrained by the solar rotation, and they produce a negative shear that, in turn, accelerates meridional motions, producing the observed surface latitudinal velocity (Miesch & Hindman 2011). Recent simulations by Kitiashvili et al (2022) showed that turbulent convection in the upper part of the NSSL can generate radial differential rotation and meridional circulation. However, it is still uncertain how the turbulent correlations generated by nonlocal convection can sustain the solar differential rotation below the NSSL.…”