Non-local thermodynamic equilibrium inversions from a 3D MHD chromospheric model
Non-local thermodynamic equilibrium inversions from a 3D MHD chromospheric model
复制标题
3D MHD 色球模型的非局部热力学平衡反演
DOI：
10.1051/0004-6361/201218825
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
J. Leenaarts
中科院分区：
文献类型：
--
作者：
Jaime de la Cruz Rodr'iguez;H. Socas;M. Carlsson;J. Leenaarts
太阳色球层的结构被认为是由磁场控制的，即使在太阳平静的地区，光球场相对较弱。在过去的十年中，反演方法已成为分析活动区色球层的有力工具。反演的适用性，以推断分层的物理条件在一个动态的三维太阳色球层尚未详细研究。
本研究的目的是建立非局部热平衡（NLTE）反演技术的塞曼效应在Ca II 8542线诱导的斯托克斯轮廓的诊断能力。
我们使用3D辐射传输代码Multi 3d对非LTE中安静的太阳大气进行3D辐射MHD模拟，在快照中计算了Ca II原子能级粒子数。这些人口被用来计算合成全斯托克斯配置文件中的Ca II 8542线使用1.5D辐射传输和反演代码妮可。然后，对轮廓进行光谱退化以考虑有限的滤波器宽度，并添加高斯噪声以考虑有限的光子通量。使用Nicole对这些剖面进行了反演，并将结果与原始模式大气进行了比较。
我们的NLTE反演适用于安静的太阳合成观测提供相当不错的估计色球磁场，视线速度和有点不太准确，但仍然非常有用，估计的温度。光子的三维散射导致色球层中的冷袋在谱线轮廓中不可见，因此它们也不能通过反演恢复。为了在该安静的快照中成功地检测斯托克斯线性偏振，低于10^{-3.5}的噪声水平是必要的。
The structure of the solar chromosphere is believed to be governed by magnetic fields, even in quiet-Sun regions that have a relatively weak photospheric field. During the past decade inversion methods have emerged as powerful tools for analyzing the chromosphere of active regions. The applicability of inversions to infer the stratification of the physical conditions in a dynamic 3D solar chromosphere has not yet been studied in detail.
This study aims to establish the diagnostic capabilities of non-local thermodynamical equilibrium (NLTE) inversion techniques of Stokes profiles induced by the Zeeman effect in the Ca II 8542 line.
We computed the Ca II atomic level populations in a snapshot from a 3D radiation-MHD simulation of the quiet solar atmosphere in non-LTE using the 3D radiative transfer code Multi3d. These populations were used to compute synthetic full-Stokes profiles in the Ca II 8542 line using 1.5D radiative transfer and the inversion code Nicole. The profiles were then spectrally degraded to account for finite filter width and Gaussian noise was added to account for finite photon flux. These profiles were inverted using Nicole and the results were compared with the original model atmosphere.
Our NLTE inversions applied to quiet-Sun synthetic observations provide reasonably good estimates of the chromospheric magnetic field, line-of-sight velocities and somewhat less accurate, but still very useful, estimates of the temperature. Three dimensional scattering of photons cause cool pockets in the chromosphere to be invisible in the line profile and consequently they are also not recovered by the inversions. To successfully detect Stokes linear polarization in this quiet snapshot, a noise level below 10^{-3.5} is necessary.