Hemispheric Magnetic Asymmetry and Cross-Equatorial Circulation Cells within the Sun's Near-Surface Shear Layer

TL;DR

This study uses 14 years of helioseismic data to analyze how hemispheric magnetic asymmetry influences near-surface solar flows and circulation cells, revealing their depth-dependent behavior and connection to magnetic flux dynamics.

Contribution

It provides new insights into the depth structure and evolution of cross-equatorial flows and their relation to hemispheric magnetic asymmetry and sunspot activity.

Findings

Hemispheric magnetic asymmetry controls flow amplitude and direction.

Flows reverse below 0.97 solar radii, forming circulation cells.

Large sunspots influence the lifetime of these circulation patterns.

Abstract

Using time-distance helioseismic measurements of meridional flow in the near-surface shear layer over a period of 14 years, starting from May 2010, we probe the depth structure and evolution of its cross-equatorial part. We confirm that the hemispheric magnetic asymmetry determines the amplitude and direction of such flows. Additionally, we find that these flows turn over and change direction at depths below 0.97R, forming circulation cells with lifetimes dictated again by the hemispheric magnetic imbalance, which is dominated by the occurrences of large sunspots. We also examine connections between cross-equatorial magnetic flux plumes and the flows, and discuss their implications for the equatorial flux cancellation/submergence and the poleward transport of flux.