Stokes imaging polarimetry using image restoration at the Swedish 1-m Solar Telescope II : A calibration strategy for Fabry-Perot based instruments
Stokes imaging polarimetry using image restoration at the Swedish 1-m Solar Telescope II : A calibration strategy for Fabry-Perot based instruments
复制标题
使用瑞典 1 米太阳望远镜 II 的图像恢复进行斯托克斯成像偏振测量：基于法布里-珀罗的仪器的校准策略
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
M. Noort
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作者：
Roald S. Schnerr;Jaime de la Cruz Rodriguez;M. Noort
瑞典1米太阳望远镜上的新CRISP过滤器提供了以前所未有的空间分辨率和节奏观测太阳大气的机会。为了从该仪器的高质量观测数据中获益，我们开发了校准和恢复偏振Stokes图像的方法，在光学和近红外波长下获得，考虑到滤光片特性的视场变化。为了便于速度测量，使用三维流体动力学颗粒模拟的时间序列来计算不同日心角下的安静太阳光谱线剖面。具有对流蓝移的合成线轮廓可以作为视距速度的绝对参考。用cai8542a线的观测资料研究了色球原纤维中的磁场。线翼显示在光球中部高度的粒状图案，而在线的核心可以看到覆盖的色球层。利用完整的斯托克斯数据，我们试图观测验证色球原纤维与磁场的排列。我们的研究结果表明，在大多数情况下，原纤维是沿着磁场方向排列的，但我们也发现了一些情况并非如此的例子。可以使用非lte反演代码对色球数据中形成的光谱线的Stokes数据进行详细解释。我们首次使用真实的3D MHD色球模拟平静的太阳，以评估NLTE反演如何从Ca II 8542 a的光谱偏振观测中恢复物理量。我们证明了反演提供了色球层中深度平均量的现实估计，尽管测量安静的太阳色球磁场需要高光谱分辨率和高灵敏度。
The new CRISP filter at the Swedish 1-m Solar Telescope provides opportunities for observing the solar atmosphere with unprecedented spatial resolution and cadence. In order to benefit from the high quality of observational data from this instrument, we have developed methods for calibrating and restoring polarized Stokes images, obtained at optical and near infrared wavelengths, taking into account field-of-view variations of the filter properties. In order to facilitate velocity measurements, a time series from a 3D hydrodynamical granulation simulation is used to compute quiet Sun spectral line profiles at different heliocentric angles. The synthetic line profiles, with their convective blueshifts, can be used as absolute references for line-of-sight velocities. Observations of the Ca II 8542 A line are used to study magnetic fields in chromospheric fibrils. The line wings show the granulation pattern at mid-photospheric heights whereas the overlying chromosphere is seen in the core of the line. Using full Stokes data, we have attempted to observationally verify the alignment of chromospheric fibrils with the magnetic field. Our results suggest that in most cases fibrils are aligned along the magnetic field direction, but we also find examples where this is not the case. Detailed interpretation of Stokes data from spectral lines formed in the chromospheric data can be made using non-LTE inversion codes. For the first time, we use a realistic 3D MHD chromospheric simulation of the quiet Sun to assess how well NLTE inversions recover physical quantities from spectropolarimetric observations of Ca II 8542 A. We demonstrate that inversions provide realistic estimates of depth-averaged quantities in the chromosphere, although high spectral resolution and high sensitivity are needed to measure quiet Sun chromospheric magnetic fields.