The Accuracy of the Center-of-Gravity Method for Measuring Velocity and Magnetic Field Strength in the Solar Photosphere
The Accuracy of the Center-of-Gravity Method for Measuring Velocity and Magnetic Field Strength in the Solar Photosphere
复制标题
重心法测量太阳光球层速度和磁场强度的精度
DOI：
10.1086/375736
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发表时间：
2003
期刊：
影响因子：
--
通讯作者：
H. Uitenbroek
中科院分区：
文献类型：
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作者：
H. Uitenbroek
研究了用重心法从空间分辨光谱线剖面反演太阳光球视线速度和磁场强度的精度。为此，通过三维太阳磁对流模拟快照的二维切片计算了一系列Fe - I线的理论非lte极化线轮廓。利用COG方法对剖面上所有位置的计算剖面进行了分析，并将提取的速度和场强值与地层高度处的实际值进行了比较。所使用的线的平均地层高度在平均光球高度以上60至近400公里之间。COG方法对于测量这些地层高度下半部分的速度和测量整个高度范围内的场强（中等强度的油田）似乎是可靠的。此外，研究表明，COG的确定与光谱分辨率无关，使其特别适用于需要高通量和相应的大光谱带通的应用，例如使用大直径望远镜进行高空间分辨率观测。最后，研究了广角散射对检索速度和场强的影响。
I investigate the accuracy with which the line-of-sight velocity and magnetic field strength in the solar photosphere can be recovered from spatially resolved spectral line profiles with the center-of-gravity (COG) method. For this purpose, theoretical non-LTE polarized line profiles of a series of Fe I lines were calculated through a two-dimensional slice from a snapshot of a three-dimensional solar magnetoconvection simulation. The calculated profiles were analyzed with the COG method for all positions along the slice, and retrieved values of velocity and field strength were compared with actual values at the heights of formation of the lines. The average formation heights of the employed lines range from 60 to almost 400 km above the average photospheric level. The COG method appears reliable for measuring velocities in the lower half of these formation heights and for measuring field strength over the whole range of heights, for fields up to intermediate strength. Moreover, it is shown that the COG determination is independent of spectral resolution, making it particularly suitable for applications that require high throughput and a correspondingly large spectral bandpass, such as high spatial resolution observations with a large-diameter telescope. Finally, the effect of broad-angle scattering, which includes a schematic representation of image deterioration through seeing, on the retrieved velocity and field strength was investigated.