Magnetic Helicity Evolution and Eruptive Activity in NOAA Active Region 11158
Magnetic Helicity Evolution and Eruptive Activity in NOAA Active Region 11158
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DOI：
10.3847/1538-4357/ac88cb
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发表时间：
2022-09
期刊：
影响因子：
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通讯作者：
L. Green;J. Thalmann;G. Valori;E. Pariat;L. Linan;K. Moraitis
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文献类型：
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作者：
L. Green;J. Thalmann;G. Valori;E. Pariat;L. Linan;K. Moraitis
日冕物质抛射是太阳最活跃的活动事件之一，但导致其发生的物理机制尚未完全了解。它们可以对地球造成重大的空间天气影响，因此了解这些喷射发生的原因和时间是准确的空间天气预报所必需的。在这项研究中，我们使用了一个4天的时间序列，称为螺旋度比，∣H J∣/∣H V∣（活动区域磁场载流部分的螺旋度与体积内总相对磁螺旋度之比），这是由NOAA活动区域11158的非线性无力场外推计算得到的。我们将∣H J∣/∣H V∣的演化与活跃区日冕中产生的活动进行了比较，并表明该比值可用于指示活跃区何时容易爆发。当∣H J∣/∣H V∣超过0.1时，就会发生这种情况，正如以前的研究所表明的那样。我们发现，在强通量出现、不同双极磁场之间的碰撞和重连、剪切运动以及通过失败和成功的喷发而重新配置日冕时，螺旋比的变化更为明显。当通量出现、碰撞和剪切运动减少时，尽管在此期间发生了显著的喷发活动，但螺旋比的变化有些微妙。
Coronal mass ejections are among the Sun’s most energetic activity events yet the physical mechanisms that lead to their occurrence are not yet fully understood. They can drive major space weather impacts at Earth, so knowing why and when these ejections will occur is required for accurate space weather forecasts. In this study we use a 4 day time series of a quantity known as the helicity ratio, ∣H J ∣/∣H V ∣ (helicity of the current-carrying part of the active region field to the total relative magnetic helicity within the volume), which has been computed from nonlinear force-free field extrapolations of NOAA active region 11158. We compare the evolution of ∣H J ∣/∣H V ∣ with the activity produced in the corona of the active region and show this ratio can be used to indicate when the active region is prone to eruption. This occurs when ∣H J ∣/∣H V ∣ exceeds a value of 0.1, as suggested by previous studies. We find the helicity ratio variations to be more pronounced during times of strong flux emergence, collision and reconnection between fields of different bipoles, shearing motions, and reconfiguration of the corona through failed and successful eruptions. When flux emergence, collision, and shearing motions have lessened, the changes in helicity ratio are somewhat subtle despite the occurrence of significant eruptive activity during this time.