Observation of all pre- and post-reconnection structures involved in three-dimensional reconnection geometries in solar eruptions

TL;DR

This study provides the first comprehensive observational evidence of all four constituents of two distinct 3D reconnection geometries involving erupting flux ropes during a solar eruption, confirming recent theoretical models.

Contribution

It uniquely identifies and characterizes all components of ar-rf and rr-rf reconnections in a single solar eruptive event, validating 3D reconnection models.

Findings

All four constituents of ar-rf and rr-rf reconnections observed.

Reconnection signatures match predictions from 3D MHD simulations.

Reconnection processes are linked to flare ribbon hook evolution.

Abstract

We report on observations of the two newly-identified reconnection geometries involving erupting flux ropes. In 3D, a flux rope can reconnect either with a surrounding coronal arcade (recently named "ar-rf" reconnection) or with itself ("rr-rf" reconnection), and both kinds of reconnection create a new flux rope field line and a flare loop. For the first time, we identify all four constituents of both reconnections in a solar eruptive event, the filament eruption of 2011 June 07 observed by SDO/AIA. The ar-rf reconnection manifests itself as shift of one leg of the filament by more than 25" northward. At its previous location, a flare arcade is formed, while the new location of the filament leg previously corresponded to a footpoint of a coronal loop in 171 A. In addition, the evolution of the flare ribbon hooks is also consistent with the occurrence of ar--rf reconnection as predicted by MHD simulations. Specifically, the growing hook sweeps footpoints of preeruptive coronal arcades, and these locations become inside the hook. Furthermore, the rr-rf reconnection occurs during the peak phase above the flare arcade, in an apparently X-type geometry involving a pair of converging bright filament strands in the erupting filament. A new flare loop forms near the leg of one of the strands, while a bright blob, representing a remnant of the same strand, is seen ascending into the erupting filament. All together, these observations vindicate recent predictions of the 3D standard solar flare model.