Effects of Solar Active Regions on Meridional Flows

Abstract

The aim of this Letter is to extend our previous study of the solar-cycle variations of meridional flows and to investigate their latitudinal and longitudinal structure in the subphotospheric layer, especially their variations in magnetic regions. Helioseismology observations indicate that mass flows around active regions are dominated by inflows into those regions. On average, those local flows are more important around the leading magnetic polarities of active regions than around the following polarities and depend on the evolutionary stage of particular active regions. We present a statistical study based on MDI/SOHO observations of 1996-2002 and show that this effect explains a significant part of the cyclic change of meridional flows in near-equatorial regions, but not at higher latitudes. A different mechanism driving solar-cycle variations of the meridional flow probably operates.