Subsurface meridional flows from ring-diagram analysis showed a clear hemispheric asymmetry in last 18 years. Interestingly, this flow asymmetry leads the magnetic flux and sunspot number asymmetry by 3.1 – 3.6 years.
Meridional flows during the solar minimum and maximum years are derived using 14 years of SOHO/MDI data. The flows changed significantly from the minimum to the maximum, and major changes were associated with the active latitudes.
It is demonstrated that when taking into account of the radial inhomogeneity of the Coriolis number, the solar-like differential rotation and the double-cell meridional circulation can both be reproduced by the mean-field model.
Various observable, such as polar field, meridional flow, and sunspot number, are examined to identify information flow, causality, and time delay between them during solar cycles. It is expected that this analysis can provide observational constraints on solar cycle models and theories.
The systematic Center-to-Limb effect in time-distance helioseismic measurements is found to be significantly frequency dependent. The dependence further varies with disk-centric distance but not with travel distance.
The Sun’s meridional flow varies with the solar cycle, and this is possibly caused by the back-reaction of the dynamo-generated magnetic field on the meridional flow due to the Lorentz force.
A new method tracking individual features in a long time series of magnetograms yields new measurements of solar differential rotation and meridional circulation rate.
Large-scale inflows form around emerging solar active regions in the near-surface layer and alter the global meridional flow patterns.
Subsurface meridional flow speed shows an anti-correlation with the magnetic flux being transported poleward above the latitude of 35°. In the lower latitude, the residual meridional flow, after a long-time mean profile is subtracted, shows converging flow toward the activity belts.
Acoustic travel time reveals an equatorward meridional flow in the middle of the solar convection zone. Inversion reveals an evidence of double-cell meridional circulation inside the Sun.