Rapid Buildup of a Magnetic Flux Rope during a Confined X2.2 Class Flare in NOAA AR 12673
Rapid Buildup of a Magnetic Flux Rope during a Confined X2.2 Class Flare in NOAA AR 12673
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NOAA AR 12673 受限 X2.2 级耀斑期间磁通量绳的快速积累
DOI：
10.3847/2041-8213/aae826
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发表时间：
2018
影响因子：
7.9
通讯作者：
Cui Jun
中科院分区：
文献类型：
--
作者：
Liu Lijuan;Cheng Xin;Wang Yuming;Zhou Zhenjun;Guo Yang;Cui Jun
磁通绳（MFR）被认为是太阳爆发的核心结构;然而，它们的形成仍然存在激烈的争论。在这里，我们报告了2017年9月6日在NOAA活动区（AR）12673发生的限制X2.2级耀斑期间MFR系统的快速建立过程，三小时后，该结构爆发为主要的日冕物质抛射（CME）伴随着X9.3级耀斑。对于X2.2耀斑，我们没有发现极紫外线昏暗，分离的耀斑带，或明确的CME签名，这表明一个局限的耀斑。对于X9.3耀斑，大规模的变暗，耀斑带的分离，和CME表明它是爆发性的。通过执行非线性无力场外推的时间序列，我们发现如下。直到爆发耀斑，MFR系统位于AR。在受限耀斑期间，MFR系统的轴向通量和磁螺旋度下限分别显著增强了约86%和260%，尽管平均扭曲数几乎没有变化。在爆发耀斑期间，这三个参数都显著降低。结果表明，在封闭和爆发耀斑期间，MFR系统的建立和释放，分别。前者可以通过扩口重连来实现。我们还计算了耀斑前主极性反转线以上衰变指数的分布，没有发现显著差异。这表明MFR系统的磁通量和螺旋度的增加可能在促进其最终爆发中起作用。
Magnetic flux ropes (MFRs) are believed to be the core structure in solar eruptions; nevertheless, their formation remains intensely debated. Here we report a rapid buildup process of an MFR system during a confined X2.2 class flare occurred on 2017 September 6 in NOAA active region (AR) 12673, three hours after which the structure erupted to a major coronal mass ejection (CME) accompanied by an X9.3 class flare. For the X2.2 flare, we do not find extreme ultraviolet dimmings, separation of its flare ribbons, or clear CME signatures, suggesting a confined flare. For the X9.3 flare, large-scale dimmings, separation of flare ribbons, and a CME show it to be eruptive. By performing a time sequence of nonlinear force-free fields extrapolations we find the following. Until the eruptive flare, an MFR system was located in the AR. During the confined flare, the axial flux and the lower bound of the magnetic helicity for the MFR system were dramatically enhanced by about 86% and 260%, respectively, although the mean twist number was almost unchanged. During the eruptive flare, the three parameters were all significantly reduced. The results evidence the buildup and release of the MFR system during the confined and the eruptive flare, respectively. The former may be achieved by flare reconnection. We also calculate the pre-flare distributions of the decay index above the main polarity inversion line and find no significant difference. It indicates that the buildup of the magnetic flux and helicity of the MFR system may play a role in facilitating its final eruption.