A New Parameter of the Photospheric Magnetic Field to Distinguish Eruptive-flare Producing Solar Active Regions
A New Parameter of the Photospheric Magnetic Field to Distinguish Eruptive-flare Producing Solar Active Regions
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DOI：
10.3847/1538-4357/ab822c
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发表时间：
2020-04
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影响因子：
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通讯作者：
P. Lin;K. Kusano;D. Shiota;S. Inoue;K. Leka;Y. Mizuno
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作者：
P. Lin;K. Kusano;D. Shiota;S. Inoue;K. Leka;Y. Mizuno
太阳耀斑和日冕物质抛射是由日冕磁场引起的喷发现象。特别是，大型喷发事件起源于具有强表面磁场的活动区域（AR）。然而，尚不清楚是什么决定了AR产生爆发耀斑和日冕物质抛射的能力，这阻碍了我们对这些现象爆发成分的启动机制的了解。在这项研究中，我们提出了一个新的参数rm来测量发生在AR中的耀斑可能爆发并产生CME的可能性。参数rm由高于阈值Tc的捻度磁通量与周围磁通量（特别是上覆磁通量）之比来定义。每个AR的rm值可以用日冕磁场的非线性无力场外推模型来估计。利用太阳动力学观测台/日震磁成像仪获得的数据，计算了29个ar在大于5.0级耀斑发生前51次的rm值。我们发现扭曲度大于0.2的磁场线的脚点可以很好地代表随后的耀斑带，而覆盖在高扭曲区域的磁场线将会限制喷发，产生受限的耀斑。判别函数分析表明，rm能够较好地区分具有产生爆发耀斑能力的ARs。
Solar flares and coronal mass ejections (CMEs) are eruptive phenomena caused by coronal magnetic fields. In particular, large eruptive events originate in active regions (AR) with strong surface magnetic fields. However, it is still unclear what determines the capability of an AR to specifically produce eruptive flares and CMEs, and this hinders our knowledge of the initiation mechanism for the eruptive component of these phenomena. In this study, we propose a new parameter rm to measure the possibility that a flare that occurs in an AR can be eruptive and produce a CME. The parameter rm is defined by the ratio of the magnetic flux of twist higher than a threshold Tc to the surrounding—and specifically, the overlying—magnetic flux. The value of rm for each AR can be estimated using nonlinear force-free field extrapolation models of the coronal magnetic field. Based on the data obtained by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager, we calculated the values of rm for 29 ARs at 51 times prior to flares larger than M5.0 class. We find that the footpoints of field lines with twist higher than 0.2 can represent the subsequent flare ribbons well, and field lines that overlie and “fence in” the highly twisted region will work to confine the eruption, generating confined flares. Discriminant function analysis is used to show that rm is moderately well able to distinguish ARs that have the capability of producing eruptive flares.