抚仙湖太阳观测和研究基地知识库

In this Letter, we present a case study of interchange reconnection between a coronal hole (CH) and a small emerging active region. The small active region emerges at the edge of the CH. Following the emergence of the small active region, the expansion of the arcade loops connecting the negative and the positive polarities of the active region can be clearly seen in 211 and 171 angstrom observations. During the emergence, the active region develops loop connections to the boundary of the CH, leading to its retreat. The latter has fast and slow phases at speeds of about 2.3 km s(-1) and 0.4 km s(-1), respectively. By the end, these newly formed closed loops occupy most of the pre-emergence CH. From the line-of-sight magnetograms observed by Solar Dynamics Observatory/Helioseismic and Magnetic Imager, the magnetic polarity in the CH is mainly positive and the leading sunspot of the active region has negative polarity. It is consistent with the condition of interchange reconnection. Moreover, the potential field source surface model is used to extrapolate the coronal magnetic fields. From a sequence of extrapolation potential fields, it is clear that the open fields in the CH close down, and the closed field at the east of the active region becomes an open field. These observations and the extrapolations of the potential fields suggest that interchange reconnection occurs between the CH and the small emerging active region and is driven by the flux emergence process.