  Helioseismology has discovered a thin layer beneath the solar surface where
the rotation rate increases rapidly with depth. The normalized rotational shear
in the upper 10 Mm of the layer is constant with latitude. Differential
rotation theory explains such a rotational state by a radial-type anisotropy of
the near-surface convection and a short correlation time of convective
turbulence compared to the rotation period. The shear layer is the main driver
of the global meridional circulation.
