Moat flow in the vicinity of sunspots for various penumbral configurations

TL;DR

This study investigates the relationship between moat flows around sunspots and penumbral configurations using high-resolution solar observations, revealing that moat flows are systematically associated with specific penumbral orientations.

Contribution

It provides the first systematic analysis linking moat flow presence to penumbral orientation, highlighting the role of magnetic structures in solar active regions.

Findings

Moat flows are mainly present when penumbrae are oriented perpendicularly to sunspot borders.

A case was observed where the typical relation did not hold, possibly due to magnetic neutral line effects.

Moat flows are strongly correlated with the existence and configuration of penumbrae.

Abstract

High-resolution time series of sunspots have been obtained with the Swedish 1m Solar Telescope between 2003 and 2006 at different locations on the solar disc. Proper motions in seven different active regions have been studied. The analysis has been done by applying local correlation tracking to every series of sunspots, each of them more than 40 minutes long. The sunspots' shapes include a different variety of penumbral configurations. We report on a systematic behaviour of the large-scale outflows surrounding the sunspots, commonly known as moat flows, that are essentially present only when preceded by a penumbra not tangential but perpendicular to the sunspot border. We present one case for which this rule appears not to be confirmed. We speculate that the magnetic neutral line, which is located in the vicinity of the anomalous region, might be responsible for blocking the outflow. These new results confirm the systematic and strong relation between the moat flows and the existence of penumbrae. A comparative statistical study between moats and standard granulation is also performed.