The formation of sunspot penumbra - Magnetic field properties
The formation of sunspot penumbra - Magnetic field properties
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太阳黑子半影的形成 - 磁场特性
DOI：
10.1051/0004-6361/201117485
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发表时间：
2012
影响因子：
6.5
通讯作者：
R. Schlichenmaier
中科院分区：
文献类型：
--
作者：
R. Rezaei;N. Bello Gonzalez;R. Schlichenmaier
目的研究NOAA 11024活动区黑子半影的磁通量出现和形成。方法在德国VTT用TIP和GFPI偏振光谱仪沿着用G波段和Ca ii K滤光片的宽带图像同时观测了光球铁谱线在1089.6 nm和617.3 nm处的Stokes参数。光球磁场矢量重建从测量的斯托克斯轮廓反演。使用AZAM代码，我们转换的倾斜线的视线（LOS）的本地参考帧（LRF）。半影的形成与倾斜磁场密切相关。在磁场强度强、倾角小的地区，不形成半影。在4.5h的观测时间内，半影区的LRF磁通量从9.7 × 1020 Mx增加到18.2 × 1020 Mx，而本影区的磁通量保持不变，约为3.8 × 1020 Mx。周围环境的磁通量被并入光斑，新的磁通量通过小通量贴片（SFP）提供，平均通量为2-3 × 1018 Mx。光斑的通量增长率为4.2 × 10 ~（16）Mx·s ~（-1），相当于每分钟合并一个SFP。在光斑半影形成过程中，a）本影的最大磁场强度不变，B）磁中性线相对于本影的位置不变，c）新的磁通量到达光斑出射侧，而半影形成在对侧，d）光桥的平均LRF倾角从50°减小到37°，e）光桥的平均LRF倾角从50°减小到37°。e）随着半影区的发展，磁斑边缘的平均磁场强度从1.0 kG下降到0.8 kG。结论与细长颗粒相关的SFP是活动区结构形成的基石。在太阳黑子的形成过程中，它们的贡献与孔隙的合并相当。除了磁场的一组关键参数外，周围安静的环境对半影的形成也很重要。光桥作为合并孔隙之间捕获的颗粒的残余物，被发现在形成过程中起着至关重要的作用。它们似乎在形成过程中引导磁通量通过斑点。光桥也是第一个半影丝形成的地方。
AimsWe study the magnetic flux emergence and formation of a sunspot penumbra in the active region NOAA 11024.MethodsWe simultaneously observed the Stokes parameters of the photospheric iron lines at 1089.6 nm with the TIP and 617.3 nm with the GFPI spectropolarimeters along with broad-band images using G-band and Ca ii K filters at the German VTT. The photospheric magnetic field vector was reconstructed from an inversion of the measured Stokes profiles. Using the AZAM code, we converted the inclination from line-of-sight (LOS) to the local reference frame (LRF).ResultsIndividual filaments are resolved in maps of magnetic parameters. The formation of the penumbra is intimately related to the inclined magnetic field. No penumbra forms in areas with strong magnetic field strength and small inclination. Within 4.5 h observing time, the LRF magnetic flux of the penumbra increases from 9.7 × 1020to 18.2 × 1020Mx, while the magnetic flux of the umbra remains constant at ~3.8 × 1020Mx. Magnetic flux in the immediate surroundings is incorporated into the spot, and new flux is supplied via small flux patches (SFPs), which on average have a flux of 2–3 × 1018Mx. The spot’s flux increase rate of 4.2 × 1016Mx s-1corresponds to the merging of one SFP per minute. We also find that, during the formation of the spot penumbra, a) the maximum magnetic field strength of the umbra does not change; b) the magnetic neutral line keeps the same position relative to the umbra; c) the new flux arrives on the emergence side of the spot while the penumbra forms on the opposite side; d) the average LRF inclination of the light bridges decreases from 50° to 37°; and e) as the penumbra develops, the mean magnetic field strength at the spot border decreases from 1.0 to 0.8 kG.ConclusionsThe SFPs associated with elongated granules are the building blocks of structure formation in active regions. During the sunspot formation, their contribution is comparable to the coalescence of pores. Besides a set of critical parameters for the magnetic field, a quiet environment in the surroundings is important for penumbral formation. As remnants of trapped granulation between merging pores, the light bridges are found to play a crucial role in the formation process. They seem to channel the magnetic flux through the spot during its formation. Light bridges are also the locations where the first penumbral filaments form.