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.

太阳的子午环流在地表是极向的，应该在一定深度处有回流。由于对流区内的湍流应力驱动着像差速旋转和子午环流这样的大规模流动，因此，这些流动有望保持在该区域内。当前的观测（基于日震学）和理论（基于发电机理论）的证据都指向对流区底部子午环流的赤道回流。假设在湍流上平均的各种量的平均值呈轴对称，我们将基于二维平均场理论研究类太阳恒星的大规模流动。旋转恒星中的湍流应力可以传递角动量，从而产生差动旋转。子午线环流是由两个力项之间的轻微不平衡引起的，它们试图以相反的方向驱动：热风力项（由于极地对流传热的效率更高而产生）和离心力项（因差而产生）回转）。为了使这些术语具有可比性，太阳的两极应比赤道稍热。我们讨论了子午线环流在通量输运发电机模型中的重要作用。Babcock-Leighton过程在表面产生的极向场向极对流，而在对流区底部产生的环形场向赤道对流。经络环流的波动（相干时间约为30-40年）有助于解释太阳周期不规则的许多方面。