SUNRISE/IMaX observations of convectively driven vortex flows in the Sun

TL;DR

This study uses Sunrise telescope data to analyze convectively driven vortex flows on the quiet Sun, revealing higher vortex occurrence rates, their durations, recurrence, and rotation characteristics, with implications for solar differential rotation effects.

Contribution

First observational characterization of vortex flows on the quiet Sun using high-resolution data, including their frequency, duration, recurrence, and rotation properties.

Findings

Vortex occurrence rate is 1.7 times higher than previous estimates.

Average vortex duration is approximately 8 minutes.

Vortices predominantly rotate counterclockwise, possibly influenced by solar differential rotation.

Abstract

We characterize the observational properties of the convectively driven vortex flows recently discovered on the quiet Sun, using magnetograms, Dopplergrams and images obtained with the 1-m balloon-borne Sunrise telescope. By visual inspection of time series, we find some 3.1e-3 vortices/(Mm^2 min), which is a factor of 1.7 larger than previous estimates. The mean duration of the individual events turns out to be 7.9 min, with a standard deviation of 3.2 min. In addition, we find several events appearing at the same locations along the duration of the time series (31.6 min). Such recurrent vortices show up in the proper motion flow field map averaged over the time series. The typical vertical vorticities are <= 6e-3 1/sec, which corresponds to a period of rotation of some 35 min. The vortices show a preferred counterclockwise sense of rotation, which we conjecture may have to do with the preferred vorticity impinged by the solar differential rotation.