Solar-Cycle Variation of the Subsurface Flows of Active and Quiet Regions

Abstract:

We study the solar-cycle variation of subsurface flows for both active and quiet solar regions. We derive the temporal variation of the zonal and meridional flows from the surface to a depth of 16 Mm using ring-diagram analysis applied to Dopplergrams obtained with the Helioseismic and Magnetic Imager (HMI) instrument onboard the Solar Dynamics Observatory (SDO) spacecraft. We use thresholds in magnetic activity to separate the flows into subsets of active and quiet regions. In addition, we derive the subset of intermediate regions that are excluded from either the quiet- or active-region subset. The subsurface flows associated with active and quiet regions show the same variation with the solar cycle with alternating bands of faster- and slower-than-average zonal and meridional flows moving from mid-latitudes toward the equator during the course of a cycle but with different amplitudes. We will derive the flow patterns of the intermediate-region subset as well and compare their amplitudes with those of the other subsets. We will study the north-south variation of the resulting flow patterns and their implications on the activity of solar cycle 25.