2017/10/18 by Shuhong Yang, Jun Zhang, Xiaoshuai Zhu +1 · 1 citation
Engineering · Physics and Astronomy · #Flare #Fluid dynamics and aerodynamics studies #Ionosphere and magnetosphere dynamics #Line (geometry) #Magnetogram #Polarity (international relations) #Protein filament #Solar and Space Plasma Dynamics #Solar flare #Solar prominence #Sunspot #astro-ph.SR
paper · pdf · doi:10.3847/2041-8213/aa9476
7 pages, 1 table, 4 figures, accepted for publication in ApJL
arxiv created 2017/10/18 · openalex publication_date 2017/11/01 · arxiv updated 2017/11/08 · openalex created_date 2017/11/10 · openalex updated_date 2026/08/05
Abstract Solar active region (AR) 12673 produced 4 X-class, 27 M-class, and numerous lower-class flares during its passage across the visible solar disk in 2017 September. Our study is to answer the questions why this AR was so flare-productive and how the X9.3 flare, the largest one of the past decade, took place. We find that there was a sunspot in the initial several days, and then two bipolar regions emerged nearby it successively. Due to the standing of the pre-existing sunspot, the movement of the bipoles was blocked, while the pre-existing sunspot maintained its quasi-circular shaped umbra only with the disappearance of a part of penumbra. Thus, the bipolar patches were significantly distorted, and the opposite polarities formed two semi-circular shaped structures. After that, two sequences of new bipolar regions emerged within the narrow semi-circular zone, and the bipolar patches separated along the curved channel. The new bipoles sheared and interacted with the previous ones, forming a complex topological system, during which numerous flares occurred. At the highly sheared region, a great deal of free energy was accumulated. On September 6, one negative patch near the polarity inversion line began to rapidly rotate and shear with the surrounding positive fields, and consequently the X9.3 flare erupted. Our results reveal that the block-induced complex structures built the flare-productive AR and the X9.3 flare was triggered by an erupting filament due to the kink instability. To better illustrate this process, a block-induced eruption model is proposed for the first time.