太阳三维流体动力学模拟的中心-边缘变化
Center-to-Limb Variation of Solar 3-D Hydrodynamical Simulations
摘要：
我们仔细研究了太阳中心到边缘的连续体和线的变化，并将观测结果与太阳表面的三维流体动力学模拟（由M。Asplund和合作者）和1-D模型大气。从3-D时间序列的强度是通过新的合成代码ASSET，它克服了以前可用的代码的局限性，包括一个一致的处理散射，并允许任意复杂的线和连续不透明。在连续体中，我们发现非常相似的合成和观察两种类型的模型大气之间的差异。这与以前的研究相反，以前的研究使用了"水平"和时间平均的3-D模型表示，并发现了与观测结果的显着更大的分歧。三维模拟中温度场和速度场的存在为再现太阳谱线形状提供了显著的优势。尽管如此，观察到的和合成的等效宽度的比较表明，3-D模型也预测更均匀的丰度作为磁盘上的位置角的函数。我们的结论是，3-D模拟不仅提供了一个更现实的描述的气体动力学，但是，尽管其简化处理的辐射传输，它也预测合理以及所观察到的中心到肢体的变化，这是一个热结构的指示从显着的系统误差。
英文摘要：
We examine closely the solar Center-to-Limb variation of continua and lines and compare observations with predictions from both a 3-D hydrodynamic simulation of the solar surface (provided by M. Asplund and collaborators) and 1-D model atmospheres. Intensities from the 3-D time series are derived by means of the new synthesis code ASSET, which overcomes limitations of previously available codes by including a consistent treatment of scattering and allowing for arbitrarily complex line and continuum opacities. In the continuum, we find very similar discrepancies between synthesis and observation for both types of model atmospheres. This is in contrast to previous studies that used a ``horizontally'' and time averaged representation of the 3-D model and found a significantly larger disagreement with observations. The presence of temperature and velocity fields in the 3-D simulation provides a significant advantage when it comes to reproduce solar spectral line shapes. Nonetheless, a comparison of observed and synthetic equivalent widths reveals that the 3-D model also predicts more uniform abundances as a function of position angle on the disk. We conclude that the 3-D simulation provides not only a more realistic description of the gas dynamics, but, despite its simplified treatment of the radiation transport, it also predicts reasonably well the observed Center-to-Limb variation, which is indicative of a thermal structure free from significant systematic errors.
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