GREGOR observations of a small flare above a sunspot

Abstract

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 0.1 nm Ca II H interference filter. Context observations from SDO/AIA, Hinode/SOT, and IRIS show that the ribbon is a part of a larger one that extends through the neighboring positive polarities and also participates in several other flares within the active region. A 140 second long time series of Ca II H images was reconstructed by means of the Multi-Frame Blind Deconvolution method, giving the respective spatial and temporal resolutions of 0".1 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 −1 . Two of them move in the opposite direction and exhibit highly correlated intensity changes, providing evidence for the presence of slipping reconnection at small spatial scales.

Commission 12: Solar Radiation and Structure

“…The German GREGOR, an open, on-axis 1.5 m telescope, has been inaugurated in mid-2012, and commenced scientific operation in 2014. First results have been presented during the IAU General Assembly in Honolulu, describing the action of slipping reconnection on a flare development, as evidenced by features resolved at the 0.1" spatial scale (Sobotka et al 2015). Efforts have also continued for the design and planning of the 2-m Indian New Large Solar Telescope (NLST), and the 4-m European Solar Telescope (EST).…”