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arXiv 0709.3340astro-ph
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一个衰变太阳黑子的流场演化

Flow Field Evolution of a Decaying Sunspot

Na Deng, Debi Prasad Choudhary, Alexandra Tritschler, Carsten Denker, Chang Liu, Haimin Wang

摘要:

利用2005年6月7日至12日6天的可见光和白光成像数据,利用时间序列的二维光谱观测资料,研究了随黑子衰减过程中黑子内部和周围的气流和水平自行的演化。在这段时间里,太阳黑子逐渐衰变成一个小孔。光谱观测是由基于法布里-珀罗的可见光成像磁力仪(VIM)和在大熊太阳天文台(BBSO)65厘米真空反射镜上运行的高阶自适应光学(AO)系统共同获得的。我们采用局部相关跟踪(LCT)的散斑重建的时间序列的白光图像约600 nm的推断水平自行,而多普勒频移的扫描\FeI线在630.15 nm的用于计算线的视线(LOS)速度与亚弧秒的分辨率。我们发现,在内部和外部半影的径向向内和向外的自行之间的分界线,分别生存的衰变阶段。特别是在半影消失后,护城河流仍然是可检测的。根据我们的观测,有三个主要的过程使太阳黑子的磁通量减少:(a)本影的碎裂,(b)移动磁特征的磁通量抵消(货币基金组织;与太阳黑子具有相同极性)遇到领先的相反极性网络和斑区,和(c)磁流变液的通量输送(与太阳黑子具有相同极性)到与太阳黑子具有相同极性的周围网络和谱斑区域。

英文摘要:

We study the evolution of the flows and horizontal proper motions in and around a decaying follower sunspot based on time sequences of two-dimensional spectroscopic observations in the visible and white light imaging data obtained over six days from June~7 to~12, 2005. During this time period the sunspot decayed gradually to a pore. The spectroscopic observations were obtained with the Fabry-Pérot based Visible-Light Imaging Magnetograph (VIM) in conjunction with the high-order adaptive optics (AO) system operated at the 65 cm vacuum reflector of the Big Bear Solar Observatory (BBSO). We apply local correlation tracking (LCT) to the speckle reconstructed time sequences of white-light images around 600 nm to infer horizontal proper motions while the Doppler shifts of the scanned \FeI line at 630.15 nm are used to calculate line-of-sight (LOS) velocities with sub-arcsecond resolution. We find that the dividing line between radial inward and outward proper motions in the inner and outer penumbra, respectively, survives the decay phase. In particular the moat flow is still detectable after the penumbra disappeared. Based on our observations three major processes removed flux from the sunspot: (a) fragmentation of the umbra, (b) flux cancelation of moving magnetic features (MMFs; of the same polarity as the sunspot) that encounter the leading opposite polarity network and plages areas, and (c) flux transport by MMFs (of the same polarity as the sunspot) to the surrounding network and plage regions that have the same polarity as the sunspot.

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