RADIATIVE MAGNETOHYDRODYNAMIC SIMULATION OF SUNSPOT STRUCTURE
RADIATIVE MAGNETOHYDRODYNAMIC SIMULATION OF SUNSPOT STRUCTURE
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DOI：
10.1088/0004-637x/691/1/640
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发表时间：
2008-08
期刊：
影响因子：
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通讯作者：
M. Rempel;M. Schüssler;M. Knoelker
中科院分区：
文献类型：
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作者：
M. Rempel;M. Schüssler;M. Knoelker
本文介绍了一个太阳黑子的三维MHD模拟结果，其光球尺寸约为20 Mm。用MURaM程序进行了模拟，该程序包括一个真实的具有部分电离和沿多个射线方向的辐射传递的状态方程。太阳黑子大体上处于松弛状态，在中央暗本影区有亮点，而在半影区有大约2-3毫米长的亮丝，中间有暗带。与本影点的形成过程类似，半本影细丝是由磁对流形成的，以上升羽流的形式出现，由于倾斜磁场的存在而被拉长；上升气流向外偏转，而磁场减弱，在羽流上部接近光学深度统一水平的位置几乎是水平的。由于物质在上升的羽状物尖尖状顶部附近堆积，导致光学深度恒定的表面向上凸起，形成了一条黑暗的通道。模拟的半影结构与观测推断的磁场互锁梳状结构吻合得很好，该结构具有Evershed喷流，沿着具有近水平磁场和垂直翻转（“扭转”）运动的暗线细丝，这些细丝嵌入在较强且倾斜较小的磁场背景中。光球谱线形成于最顶部，略高于上升羽流，因此它们不能完全感知强流以及羽流结构上部的大场倾角和明显的场强度降低。
Results of a three-dimensional MHD simulation of a sunspot with a photospheric size of about 20 Mm are presented. The simulation has been carried out with the MURaM code, which includes a realistic equation of state with partial ionization and radiative transfer along many ray directions. The largely relaxed state of the sunspot shows a division in a central dark umbral region with bright dots and a penumbra showing bright filaments of about 2–3 Mm length with central dark lanes. By a process similar to the formation of umbral dots, the penumbral filaments result from magnetoconvection in the form of upflow plumes, which become elongated by the presence of an inclined magnetic field; the upflow is deflected in the outward direction while the magnetic field is weakened and becomes almost horizontal in the upper part of the plume near the level of optical depth unity. A dark lane forms owing to the piling up of matter near the cusp-shaped top of the rising plume that leads to an upward bulging of the surfaces of constant optical depth. The simulated penumbral structure corresponds well to the observationally inferred interlocking-comb structure of the magnetic field with Evershed outflows along dark-laned filaments with nearly horizontal magnetic field and overturning perpendicular (“twisting”) motion, which are embedded in a background of stronger and less inclined field. Photospheric spectral lines are formed at the very top and somewhat above the upflow plumes, so that they do not fully sense the strong flow as well as the large field inclination and significant field strength reduction in the upper part of the plume structures.