Solar Subsurface Flows During Solar Cycle 24

Abstract:

We study the variation of subsurface flows in the presence of magnetic activity during the current solar cycle. To determine flows in the near-surface layers of the solar convection zone from the surface to a depth of about 16 Mm, we have analyzed Dopplergrams obtained with the Global Oscillation Network Group (GONG) and the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) using a dense-pack ring-diagram analysis. We will compare the zonal and meridional flows during Cycle 24 with those during Cycle 23. The zonal and meridional flows at high latitudes are now accessible thanks to HMI data. The zonal- and meridional-flow patterns track the mean latitude of activity and are precursors of magnetic activity appearing about three years before activity is visible in synoptic maps of the solar surface. The poleward branch of the zonal-flow pattern is noticeable during Cycle 24 but is considerably weaker than during the previous cycle. We will also present the latest results from global helioseismology for comparison.