Subsurface Circulations within Active Regions

TL;DR

This study uses high-resolution ring analysis to investigate subsurface flows in active regions and quiet sun, revealing distinct flow patterns, velocities, and circulation behaviors that differ significantly between these solar features.

Contribution

It provides detailed measurements of subsurface flow velocities and circulation patterns in active regions, highlighting differences from quiet sun and their impact on convection structures.

Findings

Active regions have higher zonal velocities than quiet sun by 20 m/s.

Most active regions exhibit mean inflow and cyclonic circulation at their peripheries.

Core regions of active regions show strong anticyclonic outflows (~50 m/s).

Abstract

Using high-resolution ring analysis (HRRA) we deduce subsurface flows within magnetic active regions and within quiet sun. With this procedure we are capable of measuring flows with a horizontal spatial resolution of 2 degrees 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 quiet sun at the same latitude by 20 m/s, yet active regions advect poleward at the same rate as quiet sun. We also find that almost all active regions possess a mean inflow (20-30 m/s) and a cyclonic circulation (~5 m/s) at their peripheries, whereas their cores, where the sunspots are located, are zones of strong anticyclonic outflow (~50 m/s). 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 quiet sun, active regions possess symmetric distributions.