The transformation of sunspot structures driven by an M5.0 solar flare has been reported by Dr. XU Zhe from Yunnan Observatories, Chinese Academy of Sciences. The authors found that one penumbral segment decayed and transformed into a small pore when swept by the flare ribbon. This finding has been published in The Astrophysical Journal recently.

The birth of sunspots is associated with successive emergence of magnetic flux from the interior of the sun, suggesting that the sunspot structures are mainly affected by the evolution of the inside magnetic field. Recently, the magnetic implosion theory proposed that the flare eruptions in the corona could also impact the magnetic field structures in the solar surface. However, the observational evidence supporting the magnetic implosion theory is still controversial so far.

By using the high resolution observational data from the 1-m New Vacuum Solar Telescope (NVST) in the Fuxian Solar Observatory of China, Dr. XU et al. discovered that the sunspot structures under the flaring center suffered a distinct change during the eruption. The penumbra part of the sunspot was transformed into its umbra part. Such a movement is a reverse procedure different from the normal evolution of sunspot.

This research resolved the current two controversy of the observational evidence to the magnetic implosion theory. One is that the detection of magnetic field is unreliable during the flare eruption. The other is that the structure perturbation of sunspot is still driven by the emergence of magnetic flux. These two possibilities can be excluded by the reversely evolution of sunspot structures during the flare.

This work is supported by the Natural Science Foundation of China and the CAS “Light of West China”, and Project of the Group for Innovation of Yunnan Province.

Contact:

XU Zhe, YNAO, CAS

xuzhe6249@ynao.ac.cn