Reconstruction of a Highly Twisted Magnetic Flux Rope for an Inter-active-region X-Class Solar Flare

Chaowei Jiang,Aiying Duan,Xueshang Feng,Pingbing Zuo,Yi Wang,Peng Zou

doi:10.3389/fspas.2019.00063

Abstract

Solar eruptions are manifestation of explosive release of magnetic energy in the Sun's corona. Large solar eruptions originate mostly within active regions, where strong magnetic fields concentrate on the solar surface. Here we studied the magnetic field structure for an exception, which is a peculiar GOES X1.2 flare accompanied with a very fast coronal mass ejection taking place between two active regions, where the magnetic field is relatively weak. The pre-flare magnetic field is reconstructed from the SDO/HMI vector magnetogram, using a nonlinear force-free field extrapolation method. It is found that prior to the flare, there is a highly twisted magnetic flux rope with magnetic field lines winding over 6 turns, which connects the border of a leading sunspot of one active region and the following polarity of the neighboring active region. The flux rope's configuration is highly consistent with the observed sigmoidal coronal loops and filament channels by SDO/AIA. It resides rather low-lying between the active regions such that the torus instability is not able to be triggered. Thus, it is most likely that, due to the strong magnetic twist, the kink instability of the flux rope triggers the eruption.

Highlights

The catastrophic energy-conversion phenomena, such as solar flares and coronal mass ejections (CMEs) from the sun can heavily influence the space weather and human activities in modern society
We studied the coronal magnetic field for a peculiar inter-active regions (ARs), X-class eruptive flare which occurred in a relatively weak-field region between two ARs
Using the CESE– MHD–NLFFF code and the Solar Dynamics Observatory (SDO)/HMI vector magnetogram, we reconstructed a highly twisted magnetic flux rope (MFR) before the flare, which is not found in previous NLFFF extrapolations (e.g., Wang et al, 2015)

Summary

INTRODUCTION

The catastrophic energy-conversion phenomena, such as solar flares and coronal mass ejections (CMEs) from the sun can heavily influence the space weather and human activities in modern society. Attentions have been attracted in many papers to study the CME propagation, attempting to reveal why it is significantly deflected from the solar disk center to the Mars by a longitude of over 40◦ (Mays et al, 2015; Möstl et al, 2015; Wang et al, 2015; Zheng et al, 2016; Zagainova and Fainshtein, 2018) It is still not clear what is the source magnetic field structure that triggers the eruption.

OBSERVATIONS

CORONAL MAGNETIC FIELD RECONSTRUCTION

THE MFR

CONCLUSIONS