日野太阳光学望远镜观测的本影点磁结构
Magnetic Structure of Umbral Dots Observed with Hinode Solar Optical Telescope
摘要：
利用Hinode卫星上的太阳光学望远镜对一个正在衰减的太阳黑子进行了高分辨率和无可见光的光谱观测。2007年3月2日至3月4日，目标是位于太阳表面西侧的NOAA 10944。本影包括许多连续光中约300 km大小的本影点（UD）。本文报道了根据Milne-Eddington反演的两条铁吸收线在6302埃处的磁结构和多普勒速度场。UD的磁场强度（B）、倾角（i）和多普勒速度（v）的直方图显示中心到肢体的变化。在盘中心观察，与周围环境相比，UD具有（1）稍小的场强（Δ B=-17高斯）和（2）相对蓝移（Δ v=28 m s-1）。当黑子靠近边缘时，UDs及其周围的磁场和多普勒值几乎没有差异。这种中心到边缘的变化可以通过在尖形磁化的大气中的形成高度差来理解，由于弱磁化的热气体入侵。此外，一些UD显示出振荡光变曲线，在10 min左右出现多个峰值，这可能表明存在振荡对流。我们在两个理论模型的框架下讨论了我们的结果，即整体模型（Schussler & Vogler 2006）和无场入侵模型（Spruit & Scharmer 2006）。
英文摘要：
High resolution and seeing-free spectroscopic observation of a decaying sunspot was done with the Solar Optical Telescope aboard Hinode satellite. The target was NOAA 10944 located in the west side of the solar surface from March 2 to March 4, 2007. The umbra included many umbral dots (UDs) with size of ~300 km in continuum light. We report the magnetic structures and Doppler velocity fields around UDs, based on the Milne-Eddington inversion of the two iron absorption lines at 6302 angstrom. The histograms of magnetic field strength(B), inclination angle(i), and Doppler velocity(v) of UDs showed a center-to-limb variation. Observed at disk center, UDs had (1)slightly smaller field strength (Delta B=-17 Gauss) and (2)relative blue shifts (Delta v=28 m s-1) compared to their surroundings. When the sunspot got close to the limb, UDs and their surroundings showed almost no difference in the magnetic and Doppler values. This center-to-limb variation can be understood by the formation height difference in a cusp-shaped magnetized atmosphere around UDs, due to the weakly magnetized hot gas intrusion. In addition, some UDs showed oscillatory light curves with multiple peaks around 10 min, which may indicate the presence of the oscillatory convection. We discuss our results in the frameworks of two theoretical models, the monolithic model (Schussler & Vogler 2006) and the field-free intrusion model (Spruit & Scharmer 2006).
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