Small-Scale Activity Above the Penumbra of a Fast-Rotating Sunspot
High-resolution observations of small-scale activity above the filamentary structure of a fast-rotating sunspot of NOAA Active Region 10930 are presented. The penumbral filament that intrudes into the umbra shows a central dark core and substructures. It almost approached another end of the umbra, like a light bridge. The chromospheric Ca ii H images show many jet-like structures with a bright leading edge above it. These bright jets move across the filament tips and show coordinated up and down motions. Transition region images also show brightening at the same location above the intrusion. Coronal 195 Å images suggest that one end of the bright coronal loop footpoints resides in this structure. The intrusion has opposite polarity with respect to the umbra. Strong downflows are observed at the edges along the length of the intrusion where the opposite-polarity field is enhanced. We also observe a counter-Evershed flow in the filamentary structure that also displays brightening and energy dissipation in the upper atmosphere. This scenario suggests that the jets and brightenings are caused by low-altitude reconnection driven by opposite-polarity fields and convective downflows above such structures.
KeywordsSun: photosphere Sun: magnetic fields Sun: sunspots Sun: high resolution observations
We thank the anonymous referee for constructive comments and suggestions that improved the presentation of this manuscript. CQN thanks B. Ruiz Cobo for his comments and suggestions for improving the inversion method. Hinode is a Japanese mission developed and launched by ISAS/JAXA, with NAOJ as domestic partner and NASA and STFC (UK) as international partners. It is operated by these agencies in co-operation with ESA and NSC (Norway). TRACE is a NASA Small Explorer satellite operated at the NASA Goddard Space Flight Center by NASA and Lockheed Martin. LB thanks Bal Shiksha Sadan Samiti, Udaipur (a nongovernmental organization [NGO] for supporting this research.)
Disclosure of Potential Conflicts of Interest
The authors declare that they have no conflicts of interest.
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