Persistent magnetic vortex flow at a supergranular vertex

Abstract

Context. 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. Aims. We study the relation between a persistent photospheric vortex flow and the evolution of a network magnetic element at a supergranular vertex. Methods. 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. Results. 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. Conclusions. This evolutionary behavior supports the picture presented previously, where a small flux tube becomes stable when it is surrounded by a vortex flow.

Supergranular turbulence in the quiet Sun: Lagrangian coherent structures

“…Rempel et al (2017) extended the technique for detecting objective velocity vortices developed by Haller et al (2016) to objective magnetic vortices. Silva et al (2018) applied the LAVD technique of Haller et al (2016) and the Hinode dataset of Requerey et al (2018) to detect objective velocity vortices in the quiet-Sun, and introduced a d-criterion to avoid false vortex detection.…”

The Sun’s supergranulation

“…It remains unclear whether this strong-field dynamical behaviour has anything in common with supergranulation though. The outflow in this case is centred on a strong field region whereas it is the supergranulation inflow vertices that coincide with magnetic flux concentrations in the quiet Sun (see, e.g., Requerey et al 2018).…”

Solar Vortex Tubes: Vortex Dynamics in the Solar Atmosphere

“…Kitiashvili et al 2012b;Moll et al 2012;Wedemeyer-Böhm et al 2012;Wedemeyer & Steiner 2014;Kato & Wedemeyer 2017). The vortices observed in the solar atmosphere present a radius ranging from 0.1 to around 2 Mm (Bonet et al 2010; de Souza e Almeida Silva et al 2018; Giagkiozis et al 2018) and have an average lifetime of around 0.29 minutes (Giagkiozis et al 2018), but in supergranular convection it is possible to find vortices that last for hours (Requerey et al 2018;Chian et al 2019). Swirling motions have also been detected in the chromosphere based on Ca II 8542Å and Hα line observations (Wedemeyer-Böhm & Rouppe van der Voort 2009;Shetye et al 2019).…”

“…Vortical flows in the photosphere have been investigated using velocity fields derived from both observations (Bonet et al 2010;Attie et al 2009;Bonet et al 2008;Balmaceda et al 2010;Giagkiozis et al 2018;Requerey et al 2018;Tziotziou et al 2018Tziotziou et al , 2019Shetye et al 2019) and magnetohydrodynamics (MHD) simulations (see e.g. Kitiashvili et al 2012b;Moll et al 2012;Wedemeyer-Böhm et al 2012;Wedemeyer & Steiner 2014;Kato & Wedemeyer 2017).…”