Comprehensive analysis of a filament-embedding solar active region at different stages of evolution

Astrophysical Journal Letters:  Active regions are the brightest structures seen in the solar corona, so their physical properties hold important clues to the physical mechanisms underlying coronal heating. In this work, we present a comprehensive study for a filament-embedding active region as determined from observations from multiple facilities including the Chinese Hα Solar Explorer (CHASE). The spectral resolution of CHASE is as high as 0.024 ̊A pixel−1, which enables an accurate determination of the chromospheric Doppler velocity that is especially crucial for probing the relative stable structure investigated here. We find three types of dynamic features which correspond to different thermal and magnetic properties during the investigated time period, i.e., the overlying loops – 1MK cool loops, the moss region – 2∼3 MK hot loops, and the sigmoidal filament. The overlying cool loops,which have potential field, always show Doppler blue shifts at the east footprint and Doppler red shifts at the west, indicating a pattern of ‘siphon flow‘. The moss brightening region – the hot loops in the vicinity of the filament, which have moderate sheared field, always shows downward Doppler red shifts at the chromosphere, which could be a signature of plasma condensing into the inner region adjacent to the filament. The sigmoidal filament, which have severe sheared field lines along the polarity inversion line, however shows a different Doppler velocity pattern in its middle part, i.e., an upward Doppler blue shift at the double-J shaped stage and then a downward red shift after the sigmoidal filament forms. The present work shows overall properties of the filament-embedding active region, constraining the heating mechanisms of different parts of the active region and providing hints regarding the mass loading of the embedded filament.