  The meridional circulation of the Sun, which is observed to be poleward at
the surface, should have a return flow at some depth. Since large-scale flows
like the differential rotation and the meridional circulation are driven by
turbulent stresses in the convection zone, these flows are expected to remain
confined within this zone. Current observational (based on helioseismology) and
theoretical (based on dynamo theory) evidences point towards an equatorward
return flow of the meridional circulation at the bottom of the convection zone.
Assuming the mean values of various quantities averaged over turbulence to be
axisymmetric, we study the large-scale flows in solar-like stars on the basis
of a 2D mean field theory. Turbulent stresses in a rotating star can transport
angular momentum, setting up a differential rotation. The meridional
circulation arises from a slight imbalance between two terms which try to drive
it in opposite directions: a thermal wind term (arising out of the higher
efficiency of convective heat transport in the polar regions) and a centrifugal
term (arising out of the differential rotation). To make these terms
comparable, the poles of the Sun should be slightly hotter than the equator. We
discuss the important role played by the meridional circulation in the flux
transport dynamo model. The poloidal field generated by the Babcock--Leighton
process at the surface is advected poleward, whereas the toroidal field
produced at the bottom of the convection zone is advected equatorward. The
fluctuations in the meridional circulation (with coherence time of about 30--40
yr) help in explaining many aspects of the irregularities in the solar cycle.
Finally, we discuss how the Lorentz force of the dynamo-generated magnetic
field can cause periodic variations in the large-scale flows with the solar
cycle.
