RESPONSE OF THE PHOTOSPHERIC MAGNETIC FIELD TO THE X2.2 FLARE ON 2011 FEBRUARY 15

By Shuo Wang, Chang Liu, Rui Liu, Na Deng, Yang Liu, Haimin Wang. 2011

133 citations recorded by the source corpus.

It is well known that the long-term evolution of the photospheric magnetic field plays an important role in building up free energy to power solar eruptions. Observations, despite being controversial, have also revealed a rapid and permanent variation of the photospheric magnetic field in response to the coronal magnetic field restructuring during the eruption. The Helioseismic and Magnetic Imager instrument (HMI) on board the newly launched Solar Dynamics Observatory produces seeing-free full-disk vector magnetograms at consistently high resolution and high cadence, which finally makes possible an unambiguous and comprehensive study of this important back-reaction process. In this study, we present a near disk-center, GOES-class X2.2 flare, which occurred in NOAA AR 11158 on 2011 February 15. Using the magnetic field measurements made by HMI, we obtained the first solid evidence of a rapid (in about 30 minutes) and irreversible enhancement in the horizontal magnetic field at the flaring magnetic polarity inversion line (PIL) by a magnitude of ∼30%. It is also shown that the photospheric field becomes more sheared and more inclined. This field evolution is unequivocally associated with the flare occurrence in this sigmoidal active region, with the enhancement area located in between the two chromospheric flare ribbons and the initial conjugate hard X-ray footpoints. These results strongly corroborate our previous conjecture that the photospheric magnetic field near the PIL must become more horizontal after eruptions, which could be related to the newly formed low-lying fields resulting from the tether-cutting reconnection.

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Citations in the corpus

The Interaction of Successive Coronal Mass Ejections: A Review (2016, background): “A well studied case is AR 11158 based on the SDO/HMI vector magnetograms (see, e.g., Schrijver et al., 2011, Sun et al., 2012, SOLA: Review_v4.tex; 16 March 2017; 5:40; p. 5 Wang et al., 2012, Vemareddy, Ambastha, and Maurya, 2012).”
The standard flare model in three dimensions - I. Strong-to-weak shear transition in post-flare loops (2012, background): “…observations: offsets of chromospheric ribbons from one another, along the polarity inversion line (PIL), can be seen in Chandra et al. (2009) and Wang et al. (2012); varying shear angles of segments joining pairs of bright kernels, within chromospheric ribbons, were measured in Asai et al.…”
ELECTRIC CURRENTS IN FLARE RIBBONS: OBSERVATIONS AND THREE-DIMENSIONAL STANDARD MODEL (2014, background): “These results agree with (A color version of this figure is available in the online journal.) the quantification of irreversible changes during the flare in the photospheric horizontal magnetic field quantified in Sun et al. (2012) and Wang et al. (2012).”