File:SST Hbeta core color.png

English: During September 2017, the Sun produced the most powerful flares and explosions of solar cycle 24. These events were observed with the Swedish 1-m Solar Telescope on La Palma, Spain. Unique measurements of the magnetic loop structures that formed in the aftermath of a large X8.2 solar flare on September 10, 2017 were made. The image shows the flare coronal arcade captured by the CHROMIS instrument at 0.45 Å from the center of the H-beta line, which samples the chromosphere. The loops were created by the flare through reconnection of magnetic field lines from two separate flux systems. The intense emission at the loop top indicate a region of higher density formed through the accumulation of evaporated plasma. Usually, the flare loops are too faint to be observed in polarized light. However, in this case the loops were very bright, which allowed a uniquely clean estimate of the magnetic field strength to be made at an unprecedented spatial resolution.