TY - JOUR
T1 - Evolution of Photospheric Vector Magnetic Field Associated with Moving Flare Ribbons as Seen by GST
AU - Liu, Chang
AU - Cao, Wenda
AU - Chae, Jongchul
AU - Ahn, Kwangsu
AU - Choudhary, Debi Prasad
AU - Lee, Jeongwoo
AU - Liu, Rui
AU - Deng, Na
AU - Wang, Jiasheng
AU - Wang, Haimin
N1 - Funding Information:
We thank the teams of BBSO and SDO for providing the observational data of this event. The BBSO operation is supported by NJIT and US NSF AGS 1821294 grant. The GST operation is partly supported by the Korea Astronomy and Space Science Institute and Seoul National University, and by the strategic priority research program of Chinese Academy of Science (CAS) with grant No. XDB09000000. C.L., N.D., and H.W. were supported by NASA grants NNX13AF76G, NNX13AG13G, NNX16AF72G, 80NSSC17K0016, 80NSSC18K0673, and 80NSSC18K1705, and by NSF grants AGS 1408703 and 1821294. W.C. was supported by the grants of NSF-AGS 1821294 and National Science Foundation of China (NSFC) 11729301. J.C. was supported by the Korea Astronomy and Space Science Institute under the R&D program, Development of a Solar Coronagraph on International Space Station (Project No. 2017-1-851-00), supervised by the Ministry of Science, Information and Communications Technology (ICT), and Future Planning. D.P.C. was supported by NSF grants AGS 1413686 and 1620647. J.L. was supported by NSFC grants 41331068, 11790303 (11790300), and 41774180. R.L. was supported by NSFC grants 41474151, 41774150, and 41761134088. Facilities: BBSO/GST, SDO(HMI).
Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.
PY - 2018/12/10
Y1 - 2018/12/10
N2 - The photospheric response to solar flares, also known as coronal back reaction, is often observed as sudden flare-induced changes in the vector magnetic field and sunspot motions. However, it remains obscure whether evolving flare ribbons, the flare signature closest to the photosphere, are accompanied by changes in vector magnetic field therein. Here we explore the relationship between the dynamics of flare ribbons in the chromosphere and variations of magnetic fields in the underlying photosphere, using high-resolution off-band Hα images and near-infrared vector magnetograms of the M6.5 flare on 2015 June 22 observed with the 1.6 m Goode Solar Telescope. We find that changes of photospheric fields occur at the arrival of the flare ribbon front, thus propagating analogously to flare ribbons. In general, the horizontal field increases and the field lines become more inclined to the surface. When ribbons sweep through regions that undergo a rotational motion, the fields transiently become more vertical with decreased horizontal field and inclination angle, and then restore and/or become more horizontal than before the ribbon arrival. The ribbon propagation decelerates near the sunspot rotation center, where the vertical field becomes permanently enhanced. Similar magnetic field changes are discernible in magnetograms from the Helioseismic and Magnetic Imager (HMI), and an inward collapse of coronal magnetic fields is inferred from the time sequence of nonlinear force-free field models extrapolated from HMI magnetograms. We conclude that photospheric fields respond nearly instantaneously to magnetic reconnection in the corona.
AB - The photospheric response to solar flares, also known as coronal back reaction, is often observed as sudden flare-induced changes in the vector magnetic field and sunspot motions. However, it remains obscure whether evolving flare ribbons, the flare signature closest to the photosphere, are accompanied by changes in vector magnetic field therein. Here we explore the relationship between the dynamics of flare ribbons in the chromosphere and variations of magnetic fields in the underlying photosphere, using high-resolution off-band Hα images and near-infrared vector magnetograms of the M6.5 flare on 2015 June 22 observed with the 1.6 m Goode Solar Telescope. We find that changes of photospheric fields occur at the arrival of the flare ribbon front, thus propagating analogously to flare ribbons. In general, the horizontal field increases and the field lines become more inclined to the surface. When ribbons sweep through regions that undergo a rotational motion, the fields transiently become more vertical with decreased horizontal field and inclination angle, and then restore and/or become more horizontal than before the ribbon arrival. The ribbon propagation decelerates near the sunspot rotation center, where the vertical field becomes permanently enhanced. Similar magnetic field changes are discernible in magnetograms from the Helioseismic and Magnetic Imager (HMI), and an inward collapse of coronal magnetic fields is inferred from the time sequence of nonlinear force-free field models extrapolated from HMI magnetograms. We conclude that photospheric fields respond nearly instantaneously to magnetic reconnection in the corona.
KW - Sun: activity
KW - Sun: flares
KW - Sun: magnetic fields
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U2 - 10.3847/1538-4357/aaecd0
DO - 10.3847/1538-4357/aaecd0
M3 - Article
AN - SCOPUS:85058476212
SN - 0004-637X
VL - 869
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1
M1 - 21
ER -