A segment of bald patch in AR 12673 disintegrated rapidly during solar cycle 24’s most intense flare. The horizontal magnetic field perpendicular to the polarity inversion line changed sign, while the parallel component permanently increased.
In an MHD simulation of flux emergence, a δ-sunspot is formed spontaneously by a collision of areas with opposite polarities. Driven by convective flows and counter-streaming flows, sheared polarity inversion lines form and flux ropes are created above.
A number of sunquake events were detected in the photosphere after the X9.3 flare of 6 September 2017. This analysis reported the first detection of the chromspheric response to the sunquake events using CaII and Hα observations made by the Swedish 1-meter Solar Telescope.
Waves of magnetic-field variations were observed associated with the sunquake waves that were excited by the X9.3 flare on 2017 September 6. The nature and cause of the magnetic waves are discussed after the phase relations and power distributions of the magnetic waves and Doppler-observed sunquake waves are investigated.
Two flares occurred in a same active region above a same polarity inversion line, but one had a failed CME eruption but another one had a successful CME eruption. This study explored why that was the case.
Shearing motions and sunspot rotations found in NOAA AR 12673 are believed to lead the free energy buildup and flux rope formation, which are responsible for the two successive X-class flares.
Two homologous circular-ribbon flares associated with two filament eruptions were observed and analyzed. The emergence of magnetic flux ropes helped to inject free energy into the region and drive the magnetic reconnection above it.
Rapid and irreversible changes in chromospheric magnetic field during a flare have been observed for the first time. They look surprisingly different from their photospheric counterpart.
New HMI high-cadence vector magnetograms are now available. Observations every 135 or 90 seconds reveal the rapid magnetic evolution occurring during major solar eruptions.
A statistical study of sunspot region properties yields insights on why some are flare-productive.