由各向异性辐射在Ca I 4227 $\mathrm{Å}$线的核心散射产生的相当大的线偏振信号构成了探测低太阳色球层的非均匀和动态等离子体的重要观测。在这里，我们显示的三维（3D）的辐射转移完整的频率再分布（CRD）调查线的散射偏振的磁流体动力学的3D模型的太阳大气的结果。我们不仅考虑了由模型的磁场产生的Hanle效应，而且考虑了由水平不均匀性和宏观速度梯度引起的对称性破缺。宏观速度的水平分量的空间梯度在不需要磁场的情况下产生非常显著的前向散射极化信号，而Hanle效应倾向于在模型的磁场强于约5 G的位置处使它们去极化。标准的1.5D近似被认为是不适合理解线的散射偏振，但我们引入了一种新的改进，这种近似产生的结果与完整的3D结果的定性协议。计算的偏振信号的仪器退化也进行了研究，显示了我们可以期待在即将到来的丹尼尔K。Inouye太阳望远镜。
英文摘要：
The sizable linear polarization signals produced by the scattering of anisotropic radiation in the core of the Ca I 4227 $\mathrm{Å}$ line constitute an important observable for probing the inhomogeneous and dynamic plasma of the lower solar chromosphere. Here we show the results of a three-dimensional (3D) radiative transfer complete frequency redistribution (CRD) investigation of the line's scattering polarization in a magneto-hydrodynamical 3D model of the solar atmosphere. We take into account not only the Hanle effect produced by the model's magnetic field, but also the symmetry breaking caused by the horizontal inhomogeneities and macroscopic velocity gradients. The spatial gradients of the horizontal components of the macroscopic velocities produce very significant forward scattering polarization signals without the need of magnetic fields, while the Hanle effect tends to depolarize them at the locations where the model's magnetic field is stronger than about 5 G. The standard 1.5D approximation is found to be unsuitable for understanding the line's scattering polarization, but we introduce a novel improvement to this approximation that produces results in qualitative agreement with the full 3D results. The instrumental degradation of the calculated polarization signals is also investigated, showing what can we expect to observe with the Visible Spectro-Polarimeter at the upcoming Daniel K. Inouye Solar Telescope.
Three-dimensional radiative transfer simulations of the scattering polarization of the hydrogen Ly$α$ line in a MHD model of the chromosphere-corona transition region
Statistical Study of Appearance Timing of H$α$ Postflare Loops: Simple Scaling Law Based on Radiative Cooling
Astronomical Observatory, Kyoto University（京都大学天文台）；Department of Social Data Science, Hitotsubashi University（一桥大学社会科学数据系）；Kwasan Observatory, Kyoto University（京都大学观测馆）；School of Science and Engineering, Doshisha University（同志社大学理工学部）
Long characteristics vs. short characteristics in 3D radiative transfer simulations of polarized radiation
我们比较地图的散射偏振信号从三维（3D）的辐射传输计算中的磁对流模型的太阳大气使用正式的求解器的基础上的“短特性”（SC）和“长特性”（LC）的方法。SC方法需要较少的计算工作，但已知对于倾斜视线在出射辐射中引入空间模糊。对于偏振辐射，这种效应通常更严重，因为它是一个有符号的量，并且散射偏振对模型的不均匀性很敏感。我们研究了用这种形式解算器计算出的出射谱线辐射的偏振信号的差异。我们作为一个案例研究已经发表的结果的散射偏振的Sr I $4607~\unicode{xC5}$线获得的SC方法，表明在高分辨率的网格，它是足够准确的类型的研究。一般来说，LC方法是精确计算出射辐射的首选方法，这就是为什么它现在是3D辐射转移代码PORTA的公开版本中的选项之一。
PORTA: A three-dimensional multilevel radiative transfer code for modeling the intensity and polarization of spectral lines with massively parallel computers
Center for Space and Habitability, University of Bern（伯尔尼大学空间与宜居性中心）；Faculty of Physics, Ludwig Maximilian University（慕尼黑路德维希-马克西米利安大学物理学院）；ARTORG Center for Biomedical Engineering Research, University of Bern（伯尔尼大学ARTORG生物医学工程研究中心）；University College London（伦敦大学学院）；Astronomy & Astrophysics Group, Department of Physics, University of Warwick（华威大学物理系天文学与天体物理学组）
