English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Rapid, irreversible changes of magnetic topology and sunspot structureassociated with flares have been systematically observed in recent years. Themost striking features include the increase of horizontal field at the polarityinversion line (PIL) and the co-spatial penumbral darkening. A likelyexplanation of the above phenomenon is the back reaction to the coronalrestructuring after eruptions: a coronal mass ejection carries the upwardmomentum while the downward momentum compresses the field lines near the PIL.Previous studies could only use low resolution (above 1") magnetograms andwhite-light images. Therefore, the changes are mostly observed for X-classflares. Taking advantage of the 0.1" spatial resolution and 15s temporalcadence of the New Solar Telescope at Big Bear Solar Observatory, we report indetail the rapid formation of sunspot penumbra at the PIL associated with theC7.4 flare on 2012 July 2. It is unambiguously shown that the solar granulationpattern evolves to alternating dark and bright fibril structure, the typicalpattern of penumbra. Interestingly, the appearance of such a penumbra creates anew delta sunspot. The penumbral formation is also accompanied by theenhancement of horizontal field observed using vector magnetograms from theHelioseismic and Magnetic Imager. We explain our observations as due to theeruption of a flux rope following magnetic cancellation at the PIL.Subsequently the re-closed arcade fields are pushed down towards the surface toform the new penumbra. NLFFF extrapolation clearly shows both the flux ropeclose to the surface and the overlying fields.

Study of Rapid Formation of a Delta Sunspot Associated with the 2012 July 2 C7.4 Flare Using High-resolution Observations of New Solar Telescope