Persistent Near-Surface Flow Structures from Local Helioseismology

TL;DR

This study uses local helioseismology data to analyze persistent near-surface flow structures on the Sun, estimating rotation rates and revealing potential giant cell signatures at high latitudes.

Contribution

It demonstrates that correlation analysis of near-surface flows can accurately estimate solar rotation rates and uncovers possible giant cell flow patterns at high latitudes.

Findings

Rotation rate estimates align with global helioseismology results.

Detection of a two-sided zonal flow structure at high latitudes.

Possible evidence of giant cells in solar convection.

Abstract

Near-surface flows measured by the ring-diagram technique of local helioseismology show structures that persist over multiple rotations. We examine these phenomena using data from the {\em Global Oscillation Network Group} (GONG) and the {\em Helioseismic and Magnetic Imager} (HMI) and show that a correlation analysis of the structures can be used to estimate the rotation rate as a function of latitude, giving a result consistent with the near-surface rate from global helioseismology and slightly slower than that obtained from a similar analysis of the surface magnetic field strength. At latitudes of 60$^{\circ}$ and above the HMI flow data reveal a strong signature of a two-sided zonal flow structure. This signature may be related to recent reports of "giant cells" in solar convection.