Topological Analysis of Emerging Bipole Clusters Producing Violent Solar Events


During the rising phase of Solar Cycle 24 tremendous activity occurred on the Sun with rapid and compact emergence of magnetic flux leading to bursts of flares (C to M and even X-class). We investigate the violent events occurring in the cluster of two active regions (ARs), NOAA numbers 11121 and 11123, observed in November 2010 with instruments onboard the Solar Dynamics Observatory and from Earth. Within one day the total magnetic flux increased by 70 % with the emergence of new groups of bipoles in AR 11123. From all the events on 11 November, we study, in particular, the ones starting at around 07:16 UT in GOES soft X-ray data and the brightenings preceding them. A magnetic-field topological analysis indicates the presence of null points, associated separatrices, and quasi-separatrix layers (QSLs) where magnetic reconnection is prone to occur. The presence of null points is confirmed by a linear and a non-linear force-free magnetic-field model. Their locations and general characteristics are similar in both modelling approaches, which supports their robustness. However, in order to explain the full extension of the analysed event brightenings, which are not restricted to the photospheric traces of the null separatrices, we compute the locations of QSLs. Based on this more complete topological analysis, we propose a scenario to explain the origin of a low-energy event preceding a filament eruption, which is accompanied by a two-ribbon flare, and a consecutive confined flare in AR 11123. The results of our topology computation can also explain the locations of flare ribbons in two other events, one preceding and one following the ones at 07:16 UT. Finally, this study provides further examples where flare-ribbon locations can be explained when compared to QSLs and only, partially, when using separatrices.

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We thank the Flux Emergence team led by K. Galsgaard and F. Zuccarello for fruitful discussions during the ISSI workshops in Bern, Switzerland. Data used in this article are courtesy of NASA/SDO and the AIA and HMI science teams. THEMIS is a French telescope installed in the Canary Islands and funded by CNRS/INSU. We thank the team of THEMIS for these observations and particularly V. Bommier who was the PI during the campaign and ran the UNNOFIT inversion code. This study uses data obtained at OAFA (El Leoncito, San Juan, Argentina) in the framework of the German–Argentinean HASTA/MICA Project, a collaboration of MPE, IAFE, OAFA and MPAe. CHM and GDC acknowledge financial support from the Argentinean grants PICT 2007-1790 (ANPCyT), UBACyT 20020100100733 and PIP 2009-100766 (CONICET). CHM and GDC are members of the Carrera del Investigador Científico (CONICET). YG was supported by the National Natural Science Foundation of China (NSFC) under grant numbers 11203014, 10933003 and by a grant from the 973 project 2011CB811402.

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Correspondence to C. H. Mandrini.

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Mandrini, C.H., Schmieder, B., Démoulin, P. et al. Topological Analysis of Emerging Bipole Clusters Producing Violent Solar Events. Sol Phys 289, 2041–2071 (2014).

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  • Sun: flares
  • Sun: filament eruptions
  • Sun: magnetic fields