Magnetic structures of an emerging flux region in the solar photosphere and chromosphere
Magnetic structures of an emerging flux region in the solar photosphere and chromosphere
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DOI：
10.1051/0004-6361/200913227
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发表时间：
2010-09
影响因子：
6.5
通讯作者：
Zhi Xu;A. Lagg;S. Solanki
中科院分区：
文献类型：
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作者：
Zhi Xu;A. Lagg;S. Solanki
目标。我们研究了太阳靠近圆盘中心的一个新出现的通量区的光球层和上色球层的矢量磁场和多普勒速度。方法。利用德国真空塔望远镜（VTT）上的第二代特内里费红外偏振计（TIP II）对一个年轻活跃区的光谱偏振扫描进行了分析。扫描区域包含多个太阳黑子和一个新出现的通量区。对色球He I 10 830埃和光球Si I 10 827.1埃线的全Stokes矢量进行了基于Milne-Eddington近似的反演。这提供了两个大气层中每个空间点的磁矢量和视线速度。结果。在光球中新兴通量区（EFR）的复杂磁结构与上层色球中简单得多的结构之间可以看到明显的区别。上层色球结构与在He 10 830埃三重态中看到的细长暗结构之后出现的一组新兴环一致，类似于拱形灯丝系统（AFS），而在光球层中，我们推断在出现区内存在u型环。尽管如此，一般来说，上层色球场在倾角和场强之间具有与光球场相似的线性关系：在出射区，场弱（约300 G）且水平，但在其边缘附近，场强（高达850 G）且更垂直。从光球层到上层色球层，场强在出现区下降约0.1-0.2 Gkm(-1)（甚至更小），在其边缘的太阳黑子区下降0.3-0.6 Gkm（-1）。基于色球矢量场，假设He I 10 830埃三重态沿磁场环形成，重建了三维磁场。重建的回路相当平坦，在两个脚点处都有超音速下流。本文提供了在这条线中看到的拱丝层高度增加了10 830埃的论据和证据，支持了重建环的有效性。结论。先前推导出的单个区域NOAA 9451的efr的主要色球特性也适用于另一个区域，这表明原始的主要结果可能具有更广泛的应用。主要的例外是，只有第一个区域显示了色球层中的电流片。我们提出了一个场景，其中相对复杂的光球结构演变成简单的色球结构。
Aims. We investigate the vector magnetic field and Doppler velocity in the photosphere and upper chromosphere of a young emerging flux region of the sun close to disk center. Methods. Spectropolarimetric scans of a young active region made using the second generation Tenerife Infrared Polarimeter (TIP II) on the German Vacuum Tower Telescope (VTT) are analyzed. The scanned area contained multiple sunspots and an emerging flux region. An inversion based on the Milne-Eddington approximation was performed on the full Stokes vector of the chromospheric He I 10 830 angstrom and the photospheric Si I 10 827.1 angstrom lines. This provided the magnetic vector and line-of-sight velocity at each spatial point in both atmospheric layers. Results. A clear difference is seen between the complex magnetic structure of the emerging flux region (EFR) in the photosphere and the much simpler structure in the upper chromosphere. The upper chromospheric structure is consistent with a set of emerging loops following elongated dark structures seen in the He I 10 830 angstrom triplet, similar to arch filament systems (AFS), while in the photosphere we infer the presence of U-loops within the emergence zone. Nonetheless, in general the upper chromospheric field has a similar linear relationship between inclination angle and field strength as the photospheric field: the field is weak (approximate to 300 G) and horizontal in the emergence zone, but strong (up to 850 G) and more vertical near its edges. The field strength decreases from the photosphere to the upper chromosphere by approximately 0.1-0.2 Gkm(-1) (or even less) within the emergence zone and by 0.3-0.6 Gkm(-1) in sunspots located at its edge. We reconstructed the magnetic field in 3D based on the chromospheric vector field under the assumption that the He I 10 830 angstrom triplet forms along the magnetic field loops. The reconstructed loops are quite flat with supersonic downflows at both footpoints. Arguments and evidence for an enhanced formation height of He I 10 830 angstrom in arch-filaments seen in this line are provided, which support the validity of the reconstructed loops. Conclusions. The main chromospheric properties of EFRs previously deduced for a single region NOAA 9451 are shown to be valid for another region as well, suggesting that the main original results may have a wider application. The main exception is that only the first region displayed a current sheet in the chromosphere. We propose a scenario in which the relatively complex photospheric structure evolves into the simpler chromospheric one.