Rapid enhancement of sheared evershed flow along the neutral line associated with an X6.5 flare observed by hinode

Na Deng, Chang Liu, Debi Prasad Choudhary, Haimin Wang

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10 Scopus citations


We present G-band and CaII H observations of NOAA AR 10930 obtained by Hinode/SOT on 2006 December 6 covering an X6.5 flare. The Local Correlation Tracking technique was applied to the foreshortening-corrected G-band image series to acquire horizontal proper motions in this complex βγδ active region. With the continuous high-quality, spatial and temporal resolution G-band data, we not only confirm the rapid decay of outer penumbrae and darkening of the central structure near the flaring neutral line, but also unambiguously detect for the first time the enhancement of the sheared Evershed flow (average horizontal flow speed increased from 330 3.1 to 403 4.6ms -1) along the neutral line right after the eruptive white-light flare. Post-flare CaII H images indicate that the originally fanning out field lines at the two sides of the neutral line get connected. Since penumbral structure and Evershed flow are closely related to photospheric magnetic inclination or horizontal field strength, we interpret the rapid changes of sunspot structure and surface flow as the result of flare-induced magnetic restructuring down to the photosphere. The magnetic fields turn from fanning out to inward connection causing outer penumbrae decay, meanwhile those near the flaring neutral line become more horizontal leading to stronger Evershed flow there. The inferred enhancement of horizontal magnetic field near the neutral line is consistent with recent magnetic observations and theoretical predictions of flare-invoked photospheric magnetic field change.

Original languageEnglish (US)
Article numberL14
JournalAstrophysical Journal Letters
Issue number1 PART 2
StatePublished - May 20 2011

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Sun: activity
  • Sun: flares
  • Sun: magnetic topology
  • Sun: photosphere
  • sunspots


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