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The radial gradient of the rotation rate in the near-surface shear layer(NSSL) of the Sun is independent of latitude and radius. Theoretical mean-fieldmodels have been successful in explaining this property of the solar NSSL,while global direct convection models have been unsuccessful. We investigatereason for this discrepancy by measuring the mean flows, Reynolds stress, andturbulent transport coefficients under NSSL conditions. Simulations haveminimal ingredients. These ingredients are inhomogeneity due to boundaries,anisotropic turbulence, and rotation. Parameters of the simulations are chosensuch they match the weakly rotationally constrained NSSL. The simulations probelocally Cartesian patches of the star at a given depth and latitude. The depthof the patch is varied by changing the rotation rate such that the resultingCoriolis numbers<1. We measure the turbulent transport coefficient relevant forthe non-diffusive and diffusive parts of the Reynolds stress and compare themwith predictions of current mean-field theories. A negative radial gradient ofmean flow similar to the solar NSSL is generated only at the equator wheremeridional flows are absent. At other latitudes the meridional flow iscomparable to the mean flow corresponding to differential rotation. We alsofind that meridional components of the Reynolds stress cannot be ignored.Additionally, we find that the turbulent viscosity is quenched by rotation byabout 50\% from the surface to the bottom of the NSSL. Our local simulations donot validate the explanation for the generation of the NSSL from mean-fieldtheory where meridional stresses are neglected. However, the rotationaldependence of turbulent viscosity in our simulations is in good agreement withtheoretical prediction. Our results are in qualitative agreement with globalconvection simulations in that a NSSL obtained near the equator.

Generation of mean flows in rotating anisotropic turbulence: The case of solar near-surface shear layer