Abstract
This paper studies the magnetic topology of successively erupting active regions (ARs) 11,429 and 12,371. Employing vector magnetic field observations from Helioseismic and Magnetic Imager, the pre-eruptive magnetic structure is reconstructed by a model of non-linear force-free field (NLFFF). For all the five CMEs from these ARs, the pre-eruptive magnetic structure identifies an inverse-S sigmoid consistent with the coronal plasma tracers in EUV observations. In all the eruption cases, the quasi-separatrix layers (QSLs) of large Q values are continuously enclosing core field bipolar regions in which inverse-S shaped flare ribbons are observed. These QSLs essentially represent the large connectivity gradients between the domains of twisted core flux within the inner bipolar region and the surrounding potential like arcade. It is consistent with the observed field structure largely with the sheared arcade. The QSL maps in the chromosphere are compared with the flare-ribbons observed at the peak time of the flares. The flare ribbons are largely inverse-S shape morphology with their continuity of visibility is missing in the observations. For the CMEs in the AR 12371, the QSLs outline the flare ribbons as a combination of two inverse J-shape sections with their straight parts being separated. These QSLs are typical with the weakly twisted flux rope. Similarly, for the CMEs in the AR 11429, the QSLs are co-spatial with the flare ribbons both in the middle of the PIL and in the hook sections. In the frame work of standard model of eruptions, the observed flare ribbons are the characteristic of the pre-eruptive magnetic structure being sigmoid which is reproduced by the NLFFF model with a weakly twisted flux rope at the core.
Highlights
Most often the coronal mass ejections are seen to launch from magnetically concentrated regions called active regions (ARs)
This paper studies the magnetic topology of successively erupting active regions (ARs) 11,429 and 12,371
The coronal field is constructed by nonlinear force-free field (NLFFF) [32], we computed the chromospheric quasi-separatrix layers (QSLs) to compare their spatial locations with the geometry of the observed flare ribbons
Summary
Most often the coronal mass ejections are seen to launch from magnetically concentrated regions called active regions (ARs). The S-shaped bald-patch separatrix surface (BPSS) bifurcates into a double J-shaped QSL with the main body of the MFR lifted off From this BPSS topology, the QSL structure underneath the rising flux rope develops an X-line configuration referred to as hyperbolic flux tube (HFT), where the reconnection sets in for the onset of the eruption. Motivated by the above topological studies of the erupting regions, in this paper, we study the pre-eruptive magnetic structure of five CMEs from two successively erupting ARs. The coronal field is constructed by NLFFF [32], we computed the chromospheric QSLs to compare their spatial locations with the geometry of the observed flare ribbons.
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