Formation of a Magnetic Flux Rope in the Early Emergence Phase of NOAA Active Region 12673
Formation of a Magnetic Flux Rope in the Early Emergence Phase of NOAA Active Region 12673
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NOAA 活动区 12673 早期出现阶段磁通绳的形成
DOI：
10.3847/1538-4357/ab3c6c
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发表时间：
2019-08
期刊：
影响因子：
--
通讯作者：
Zhenjun Zhou
中科院分区：
文献类型：
--
作者：
Lijuan Liu;Xin Cheng;Yuming Wang;Zhenjun Zhou
在这项工作中，我们研究了NOAA活动区域12673在其早期出现阶段在中心极性反转线（PIL）上方的磁通绳（MFR）的形成。通过分析光球矢量磁场、极紫外（EUV）和紫外（UV）图像、外推三维（3D）非线性无力场（nlfff）以及光球运动，我们发现随着中心区域不同双极的相继出现，共轭极性分离，导致非共轭相反极性之间的碰撞。近势环首先出现在PIL上方，然后在碰撞位置被剪切并合并，如2017年9月4日出现的连续EUV s型，这也表明MFR的形成。三维nlfff进一步揭示了MFR的逐渐累积，伴随着碰撞位置的两个细长秃斑（bp）的出现，以及bp之间非常低的双曲通量管结构。最终的MFR具有相对稳定的轴向磁通，平均扭转数分别约为$2.1\ × 10^{20}$~Mx和-1.5。当碰撞发生时，在bp附近发现剪切运动，同时观察到通量抵消和紫外线增亮，表明发展了称为“碰撞剪切”的过程（由Chintzoglou等人于2019年首次发现）。结果清楚地表明，MFR是由“碰撞剪切”形成的，即在非共轭极性出现时，由它们之间的碰撞驱动剪切和通量抵消。
In this work, we investigate the formation of a magnetic flux rope (MFR) above the central polarity inversion line (PIL) of NOAA Active Region 12673 during its early emergence phase. Through analyzing the photospheric vector magnetic field, extreme ultraviolet (EUV) and ultraviolet (UV) images, extrapolated three-dimensional (3D) non-linear force-free fields (NLFFFs), as well as the photospheric motions, we find that with the successive emergence of different bipoles in the central region, the conjugate polarities separate, resulting in collision between the non-conjugated opposite polarities. Nearly-potential loops appear above the PIL at first, then get sheared and merge at the collision locations as evidenced by the appearance of a continuous EUV sigmoid on 2017 September 4, which also indicates the formation of an MFR. The 3D NLFFFs further reveal the gradual buildup of the MFR, accompanied by the appearance of two elongated bald patches (BPs) at the collision locations and a very low-lying hyperbolic flux tube configuration between the BPs. The final MFR has relatively steady axial flux and average twist number of around $2.1\times 10^{20}$~Mx and -1.5, respective. Shearing motions are found developing near the BPs when the collision occurs, with flux cancellation and UV brightenings being observed simultaneously, indicating the development of a process named as "collisional shearing" (firstly identified by Chintzoglou et al. 2019). The results clearly show that the MFR is formed by "collisional shearing", i.e., through shearing and flux cancellation driven by the collision between non-conjugated opposite polarities during their emergence.
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DOI：
10.1086/421238
发表时间：
2004-07
期刊：
The Astrophysical Journal
影响因子：
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作者：
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DOI：
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DOI：
10.3847/1538-4357/aaf3b7
发表时间：
2019
期刊：
The Astrophysical Journal
影响因子：
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作者：
Peng Zou;Chaowei Jiang;Xueshang Feng;Pingbing Zuo;Yulei Wang;Fengsi Wei
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DOI：
10.3847/0004-637x/832/1/1
发表时间：
2016-11
期刊：
The Astrophysical Journal
影响因子：
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作者：
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通讯作者：
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影响因子：
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作者：
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通讯作者：
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