Flux rope proxies and fan-spine structures in active region NOAA 11897⋆
1 Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing, PR China
2 University of Chinese Academy of Sciences, 100049 Beijing, PR China
Received: 4 May 2016
Accepted: 28 June 2016
Context. Flux ropes are composed of twisted magnetic fields and are closely connected with coronal mass ejections. The fan-spine magnetic topology is another type of complex magnetic fields. It has been reported by several authors, and is believed to be associated with null-point-type magnetic reconnection.
Aims. We try to determine the number of flux rope proxies and reveal fan-spine structures in the complex active region (AR) NOAA 11897.
Methods. Employing the high-resolution observations from the Solar Dynamics Observatory (SDO) and the Interface Region Imaging Spectrograph (IRIS), we statistically investigated flux rope proxies in NOAA AR 11897 from 14 November 2013 to 19 November 2013 and display two fan-spine structures in this AR.
Results. For the first time, we detect flux rope proxies of NOAA 11897 for a total of 30 times in four different locations during this AR’s transference from solar east to west on the disk. Moreover, we notice that these flux rope proxies were tracked by active or eruptive material of filaments 12 times, while for the remaining 18 times they appeared as brightenings in the corona. These flux rope proxies were either tracked in both lower and higher temperature wavelengths or only detected in hot channels. None of these flux rope proxies was observed to erupt; they faded away gradually. In addition to these flux rope proxies, we detect for the first time a secondary fan-spine structure. It was covered by dome-shaped magnetic fields that belong to a larger fan-spine topology.
Conclusions. These new observations imply that many flux ropes can exist in an AR and that the complexity of AR magnetic configurations is far beyond our imagination.
Key words: Sun: activity / Sun: atmosphere / Sun: coronal mass ejections (CMEs) / Sun: evolution / Sun: filaments, prominences / Sun: magnetic fields
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