Study of rapid formation of A δ sunspot associated with the 2012 July 2 C7.4 flare using high-resolution observations of the new solar telescope

Haimin Wang, Chang Liu, Shuo Wang, Na Deng, Yan Xu, Ju Jing, Wenda Cao

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Rapid, irreversible changes of magnetic topology and sunspot structure associated with flares have been systematically observed in recent years. The most striking features include the increase of the horizontal field at the polarity inversion line (PIL) and the co-spatial penumbral darkening. A likely explanation of the above phenomenon is the back reaction to the coronal restructuring after eruptions: a coronal mass ejection carries the upward momentum while the downward momentum compresses the field lines near the PIL. Previous studies could only use low-resolution (above 1″) magnetograms and white-light images. Therefore, the changes are mostly observed for X-class flares. Taking advantage of the 0.″1 spatial resolution and 15 s temporal cadence of the New Solar Telescope at the Big Bear Solar Observatory, we report in detail the rapid formation of sunspot penumbra at the PIL associated with the C7.4 flare on 2012 July 2. It is unambiguously shown that the solar granulation pattern evolves to an alternating dark and bright fibril structure, the typical pattern of penumbra. Interestingly, the appearance of such a penumbra creates a new δ sunspot. The penumbral formation is also accompanied by the enhancement of the horizontal field observed using vector magnetograms from the Helioseismic and Magnetic Imager. We explain our observations as being due to the eruption of a flux rope following magnetic cancellation at the PIL. Subsequently, the re-closed arcade fields are pushed down toward the surface to form the new penumbra. NLFFF extrapolation clearly shows both the flux rope close to the surface and the overlying fields.

Original languageEnglish (US)
Article numberL24
JournalAstrophysical Journal Letters
Volume774
Issue number2
DOIs
StatePublished - Sep 10 2013

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Sun: activity
  • Sun: atmosphere
  • Sun: coronal mass ejections (CMEs)
  • Sun: flares
  • Sun: magnetic fields

Fingerprint Dive into the research topics of 'Study of rapid formation of A δ sunspot associated with the 2012 July 2 C7.4 flare using high-resolution observations of the new solar telescope'. Together they form a unique fingerprint.

Cite this