Subsurface Circulations within Active Regions

Abstract

Using high-resolution ring analysis, we deduce subsurface flows within magnetic active regions and within the quiet Sun. With this procedure, we are capable of measuring flows with a horizontal spatial resolution of 2° in heliographic angle (or roughly 20 Mm). From the resulting flow fields we deduce mean inflow rates into active regions, mean circulation speeds around active regions, and probability density functions (PDFs) of properties of the flow field. These analyses indicate that active regions have a zonal velocity that exceeds that of the quiet Sun at the same latitude by 20 m s^-1, yet active regions advect poleward at the same rate as the quiet Sun. We also find that almost all active regions possess a mean inflow (20-30 m s^-1) and a cyclonic circulation (≈5 m s^-1) at their peripheries, whereas their cores, where the sunspots are located, are zones of strong anticyclonic outflow (≈50 m s^-1). From the PDFs, we find that active regions modify the structure of convection with a scale greater than that of supergranulation. Instead of possessing an asymmetry between inflows and outflows (with a larger percentage of the surface occupied by outflows), as is seen in the quiet Sun, active regions possess symmetric distributions.