Reevaluation of the Magnetic Structure and Evolution Associated with the Bastille Day Flare on 2000 July 14
Reevaluation of the Magnetic Structure and Evolution Associated with the Bastille Day Flare on 2000 July 14
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DOI：
10.1086/430418
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发表时间：
2005-07
期刊：
影响因子：
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通讯作者：
Haimin Wang;Chang Liu;Yuanyong Deng;Hongqi Zhang
中科院分区：
文献类型：
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作者：
Haimin Wang;Chang Liu;Yuanyong Deng;Hongqi Zhang
2000年7月14日的巴士底日耀斑被几个空间和地面观测站很好地观测到，并被许多研究人员广泛研究。最近，我们发现大部分X级耀斑与一个非常有趣的δ黑子演化模式有关：在大耀斑之后，部分外部δ黑子结构迅速衰减;同时，中央本影和/或半影结构变得更暗。这些变化发生在大约1小时内，并且是永久性的。我们发现活动区NOAA AR 9077具有与2000年7月14日X5.7耀斑相似的黑子结构变化。我们提供了额外的证据，支持我们检测到的真实的变化后，耀斑的太阳黑子结构。本文提出的新证据包括：（1）耀斑发生后，半影衰变区的Evershed速度明显减弱，表明半影结构确实在减弱;（2）根据耀斑前后的矢量磁图，半影衰变区的横向场强下降，耀斑中性线附近的横向场强明显增加;（3）耀斑爆发后，在耀斑中性线附近发现了一个新的电流系统，（4）耀斑爆发后，相反磁极性的质心位置立即向磁中性线收敛，活动区的磁通量随耀斑爆发而逐渐减小。没有耀斑模型能够解释观测的所有方面。一个简单的四极磁重联模型可以解释我们的大部分观测结果：两个磁偶极子在耀斑前以δ位形结合;磁重联产生了两组新的环：一个紧凑的耀斑环和一个可能是CME源的大规模膨胀环。由于这种重连，外部半影场变得更加垂直，对应于半影衰变。伴随着耀斑的磁重联，磁中性线附近的重联场首先增强，然后随着它的下沉而逐渐减弱。然而，这个模型从观测的一个方面来看是有问题的：我们未能确定这个四极磁场重联的两个远端足点。我们还讨论了其他现有的耀斑模型在我们的观察。
The Bastille Day flare on 2000 July 14 was well observed by several space- and ground-based observatories and studied extensively by many researchers. Recently, we discovered that a large fraction of X-class flares are associated with a very interesting evolutionary pattern in δ sunspots: part of the outer δ spot structure decays rapidly after major flares; in the meantime, central umbral and/or penumbral structure becomes darker. These changes take place in about 1 hour and are permanent. We find that the active region NOAA AR 9077 has sunspot structure change similar to that associated with the 2000 July 14 X5.7 flare. We provide additional evidence supporting that we detected the real change in the sunspot structure after the flare. The new evidence presented in this paper include the following: (1) the Evershed velocity of decayed penumbral segments was weakened significantly following the flare, indicating actual weakening of penumbral structure; (2) based on available vector magnetograms before and after the flare, the transverse field strength decreased at the areas of penumbral decay and increased significantly near the flaring neutral line; (3) a new electric current system is found near the flare neutral line after the flare; and (4) the center-of-mass positions of opposite magnetic polarities converged toward magnetic neutral line immediately following the onset of the flare, and magnetic flux of the active region decreased steadily following the flare. There is no flare model capable of interpreting all the aspects of observations. A simple quadrupolar magnetic reconnection model may explain most of our observations: two magnetic dipoles join at the δ configuration before the flare; magnetic reconnection creates two new sets of loops: a compact flare loop and a large-scale expanding loop that might be the source of the CME. The outer penumbral fields become more vertical due to this reconnection, corresponding to the penumbral decay. Following initiation of magnetic reconnection associated with the flare, reconnected fields near the magnetic neutral line are first enhanced, then gradually weakened as it submerges. However, this model is questionable from one aspect of the observations: we failed to identify two far-end footpoints of this quadrupolar magnetic reconnection. We discuss other existing flare models in the context of our observations as well.