Flare-productive Active Regions: Hinode’s View and Beyond

Based on our recently published Living Reviews article on “flare-productive active regions” (Toriumi & Wang, 2019, LRSP, 16, 3), we give an overview of the key observational features of flaring regions and physical models to explain them. It is shown that the improvement of observational techniques in the last decades including Hinode’s trio instruments has greatly advanced our understanding. For example, vector magnetograms obtained by the Solar Optical Telescope revealed the development of magnetic shear around the polarity inversion lines and are now widely used as bottom boundary conditions for the coronal field reconstruction models such as non-linear force-free field extrapolations. The EUV Imaging Spectrometer detected non-thermal broadening of coronal emission lines in the pre-flare stage, whereas the creation of sigmoidal structures seen in the X-Ray Telescope images give us a clue to the coronal response to the photospheric driving. In the presentation, we also discuss the outstanding issues and future perspective, such as the possible observation targets of the Solar-C_EUVST, other solar missions, and large aperture ground-based telescopes.