Converging Flows in the Penumbra of a δ Sunspot
Converging Flows in the Penumbra of a δ Sunspot
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δ 太阳黑子半影中的汇聚流
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
T. Shimizu
中科院分区：
文献类型：
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作者：
B. Lites;H. Socas;A. Skumanich;T. Shimizu
在太阳黑子边缘附近观测到的δ-配置的半暗带的多普勒速度表明，气流聚集在分离局部正负极性磁场的线（极性反转线）上。这些流持续了好几个小时。利用先进斯托克斯偏振仪（ASP）对该区域的观测显示出一个凸矢量场几何形状，磁力线从正极性向上拱起，然后向下拱到负极性。对多普勒速度和矢量场信息的直接解释导致了一种站不住脚的物理情况：如果流体从两个足点流向拱形磁力线的顶部，质量将迅速加载到拱形的顶部。然而，没有观测到的证据表明这种载荷所需要的动力学。为了更好地理解这种明显的矛盾，我们在极性反转线附近对观测到的Stokes谱剖面进行了双分量分析，以提取有关未解析的磁场结构及其相关流的信息。通过使用两种不同的反演技术获得的观测剖面的拟合结果强烈表明，与简单太阳黑子的半影一样，会聚区的场几何形状是“凹槽”的。然而，与简单的太阳黑子不同的是，太阳黑子的磁场分量中只有一个向外方向的Evershed流，我们的分析显示，在每个空间点上，两个分量的流动方向相反。我们将这些观测结果解释为在极性反转附近有一个交错的场线系统，由此汇聚的流能够彼此滑过并向下返回到太阳内部。
Doppler velocities in the penumbra of a δ-configuration sunspot observed near the limb indicate flows that converge upon the line separating locally positive and negative polarity magnetic field (the polarity inversion line). These flows persist for many hours. Observations of this region with the Advanced Stokes Polarimeter (ASP) reveal a convex vector field geometry with magnetic lines of force arching upward from positive polarity, then downward to negative polarity. The straightforward interpretation of the combined Doppler velocity and vector field information leads to an untenable physical situation: were flows directed from both footpoints toward the tops of arched magnetic lines of force, mass would rapidly load the tops of the arches. However, there is no observational evidence of the dynamics that such a loading would require. To better understand this apparent contradiction, we perform two-component analyses of the observed Stokes spectral profiles in the vicinity of the polarity inversion line, in order to extract information about unresolved structure of the magnetic field and its associated flows. Fits to the observed profiles, obtained by use of two different inversion techniques, suggest strongly that, as in penumbrae of simple sunspots, the field geometry in the convergence zone is "fluted." However, unlike in simple sunspots, which have only an outward-directed Evershed flow in the more horizontal of the field components, at each spatial point our analysis reveals flows in the two components that are oppositely directed. We interpret these observations as indicative of an interleaved system of field lines in the vicinity of the polarity reversal, whereby the convergent streams are able to slip past one another and return downward into the solar interior.