Origin of the Near-Surface Shear Layer of Solar Rotation

Helioseismology has revealed an increase in the rotation rate with depth in a thin (\({\sim}30\) Mm) near-surface layer. The normalized rotational shear in this layer does not depend on latitude. This rotational state is shown to be a consequence of the short characteristic time of near-surface convection compared to the rotation period and radial anisotropy of convective turbulence. Analytical calculations within mean-field hydrodynamics reproduce the observed normalized rotational shear and are consistent with numerical experiments on radiative hydrodynamics of solar convection. The near-surface shear layer is the source of global meridional flow important for the solar dynamo.