# Expanding and Contracting Coronal Loops as Evidence of Vortex Flows Induced by Solar Eruptions

## TL;DR

This study provides observational evidence of vortex flows in eruptive solar flares, demonstrating how coronal loops expand and contract in patterns consistent with vortex dynamics predicted by models.

## Contribution

It offers the first direct observational confirmation of vortex flows in solar eruptions, linking loop motions to vortex dynamics predicted by theoretical models.

## Key findings

- Coronal loops exhibit simultaneous expansion and contraction during flares.
- Vortex flows explain the observed loop motions in both X-class and C-class flares.
- Loop behaviors persist for over 35 minutes in some cases.

## Abstract

Eruptive solar flares were predicted to generate large-scale vortex flows at both sides of the erupting magnetic flux rope. This process is analogous to a well-known hydrodynamic process creating vortex rings. The vortices lead to advection of closed coronal loops located at peripheries of the flaring active region. Outward flows are expected in the upper part and returning flows in the lower part of the vortex. Here, we examine two eruptive solar flares, an X1.1-class flare SOL2012-03-05T03:20 and a C3.5-class SOL2013-06-19T07:29. In both flares, we find that the coronal loops observed by the Atmospheric Imaging Assembly in its 171\,\AA, 193\,\AA, or 211\,\AA~passbands show coexistence of expanding and contracting motions, in accordance with the model prediction. In the X-class flare, multiple expanding/contracting loops coexist for more than 35 minutes, while in the C-class flare, an expanding loop in 193\,\AA~appears to be close-by and co-temporal with an apparently imploding loop arcade seen in 171\,\AA. Later, the 193\,\AA~loop also switches to contraction. These observations are naturally explained by vortex flows present in a model of eruptive solar flares.