Subsurface Meridional Circulation in the Active Belts

TL;DR

This study analyzes subsurface meridional flow variations over five years, accounting for magnetic activity contamination, and finds persistent circulation patterns suggesting organized global flows.

Contribution

It systematically examines the impact of active regions on meridional flow measurements and reveals persistent circulation patterns even after removing magnetic activity influences.

Findings

Meridional flow amplitude increases towards solar minimum.

Residual circulation persists in active belts after removing magnetic regions.

Global organized flow patterns are suggested by the residual circulation.

Abstract

Temporal variations of the subsurface meridional flow with the solar cycle have been reported by several authors. The measurements are typically averaged over periods of time during which surface magnetic activity existed in the regions were the velocities are calculated. The present work examines the possible contamination of these measurements due to the extra velocity fields associated with active regions plus the uncertainties in the data obtained where strong magnetic fields are present. We perform a systematic analysis of more than five years of GONG data and compare meridional flows obtained by ring-diagram analysis before and after removing the areas of strong magnetic field. The overall trend of increased amplitude of the meridional flow towards solar minimum remains after removal of large areas associated with surface activity. We also find residual circulation toward the active belts that persist even after the removal of the surface magnetic activity, suggesting the existence of a global pattern or longitudinally-located organized flows.