Persistent magnetic vortex flow at a supergranular vertex

TL;DR

This study reveals a persistent photospheric vortex flow at a supergranular vertex, demonstrating its role in magnetic element evolution and flux tube stability over a 24-hour period.

Contribution

It provides the first detailed observational evidence linking long-lived vortex flows with magnetic element dynamics at supergranular vertices.

Findings

A vortex flow persists for 24 hours at a supergranular vertex.

Magnetic elements are concentrated and evacuated by vortex flows.

Magnetic features weaken and fragment after vortex disappearance.

Abstract

Photospheric vortex flows are thought to play a key role in the evolution of magnetic fields. Recent studies show that these swirling motions are ubiquitous in the solar surface convection and occur in a wide range of temporal and spatial scales. Their interplay with magnetic fields is poorly characterized, however. We study the relation between a persistent photospheric vortex flow and the evolution of a network magnetic element at a supergranular vertex. We used long-duration sequences of continuum intensity images acquired with Hinode and the local correlation-tracking method to derive the horizontal photospheric flows. Supergranular cells are detected as large-scale divergence structures in the flow maps. At their vertices, and cospatial with network magnetic elements, the velocity flows converge on a central point. One of these converging flows is observed as a vortex during the whole 24 h time series. It consists of three consecutive vortices that appear nearly at the same location. At their core, a network magnetic element is also detected. Its evolution is strongly correlated to that of the vortices. The magnetic feature is concentrated and evacuated when it is caught by the vortices and is weakened and fragmented after the whirls disappear. This evolutionary behavior supports the picture presented previously, where a small flux tube becomes stable when it is surrounded by a vortex flow.