An Eruptive Circular-ribbon Flare with Extended Remote Brightenings

TL;DR

This paper analyzes a rare eruptive circular-ribbon solar flare, detailing the magnetic reconnection processes, filament formation, and the extended remote brightenings observed during the event.

Contribution

It provides a comprehensive observation of the entire evolution of a flux rope from formation to eruption in a circular-ribbon flare, combining multiwavelength data with magnetic field modeling.

Findings

Filament forms via reconnection between sheared arcades.

Null point reconnection generates circular ribbon and remote brightenings.

Flux rope eruption causes broad remote brightenings and coronal dimmings.

Abstract

We study an eruptive X1.1 circular-ribbon flare on 2013 November 10, combining multiwavelength observations with a coronal field reconstruction using a non-force-free field method. In the first stage, a filament forms via magnetic reconnection between two mildly twisted sheared arcades, which are embedded under the fan dome associated with a null point. This reconnection seems to be driven by photospheric shearing and converging flows around the inner two arcade footpoints, consistent with the flare-related changes of transverse field. The southern portion of the filament rises upward due to torus instability and pushes against the null point. The induced null point reconnection then generates the circular ribbon and the initial remote brightening in the west, as accelerated electrons precipitate along the fan and propagate outward along quasi-separatix surfaces with high values of the squashing factor (Q) in the envelope fields, which have a curtain-like shape here. In the second stage, the southern end of the flux rope breaks away from the surface, sequentially disrupts the dome and overlying fields, and erupts in a whipping-like fashion to become a partial halo coronal mass ejection. This leads to an enhanced flare emission and fast-moving remote brightenings at the footpoints of the magnetic curtain, which span a remarkably broad region and are also associated with coronal dimmings. This is a rare example of eruptive circular-ribbon flares, in which the evolution of a flux rope from its formation to successful eruption out of the dome and the resulting unusually extended remote brightenings are completely observed.