Slipping reconnection in a solar flare observed in high resolution with the GREGOR solar telescope

TL;DR

This study uses high-resolution observations from the GREGOR solar telescope to analyze small-scale slipping reconnection events in a solar flare ribbon, revealing detailed dynamics and velocities of bright knots.

Contribution

First high-resolution imaging of slipping reconnection in a solar flare ribbon, providing detailed measurements of knot motions and intensity correlations.

Findings

Some bright knots are stationary while others move at 7-11 km/s.

Two knots move in opposite directions with correlated intensity changes.

Evidence of slipping reconnection at small spatial scales.

Abstract

A small flare ribbon above a sunspot umbra in active region 12205 was observed on November 7, 2014, at 12:00 UT in the blue imaging channel of the 1.5 m GREGOR telescope, using a 1 A Ca II H interference filter. Context observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO), the Solar Optical Telescope (SOT) onboard Hinode, and the Interface Region Imaging Spectrograph (IRIS) show that this ribbon is part of a larger one that extends through the neighboring positive polarities and also participates in several other flares within the active region. We reconstructed a time series of 140 seconds of Ca II H images by means of the multiframe blind deconvolution method, which resulted in spatial and temporal resolutions of 0.1 arcsec and 1 s. Light curves and horizontal velocities of small-scale bright knots in the observed flare ribbon were measured. Some knots are stationary, but three move along the ribbon with speeds of 7-11 km/s. Two of them move in the opposite direction and exhibit highly correlated intensity changes, which provides evidence of a slipping reconnection at small spatial scales.