Non-local thermodynamic equilibrium inversions from a 3D magnetohydrodynamic chromospheric model
Non-local thermodynamic equilibrium inversions from a 3D magnetohydrodynamic chromospheric model
复制标题
3D 磁流体动力学色球模型的非局部热力学平衡反演
DOI：
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发表时间：
2012
期刊：
影响因子：
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通讯作者：
J. Leenaarts
中科院分区：
文献类型：
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作者：
J. D. L. C. Rodríguez;H. Socas;M. Carlsson;J. Leenaarts
语境。太阳色球层的结构被认为是受磁场控制的，即使是在光球场相对较弱的安静太阳区域也是如此。在过去的十年中，反演方法已成为分析活跃区域色球层的强大工具。利用反演来推断动态 3D 太阳色球层中物理条件的分层的适用性尚未得到详细研究。目标。本研究旨在建立由 Ca ii λ 8542 Å 线中的塞曼效应引起的斯托克斯剖面的非局部热力学平衡 (NLTE) 反演技术的诊断能力。方法。我们使用 3D 辐射传输代码 Multi3d，计算了非 LTE 中安静太阳大气的 3D 辐射 MHD 模拟快照中的 Ca ii 原子级布居数。这些群体被用来使用 1.5D 辐射传输和反演代码 Nicole 计算 Ca ii λ 8542 Å 线中的合成全斯托克斯剖面。然后对轮廓进行光谱降级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 对这些剖面进行反演，并将结果与原始模型大气进行比较。结果。我们应用于安静太阳合成观测的 NLTE 反演提供了对色球磁场、视线速度的相当好的估计，以及对温度的估计，虽然不太准确，但仍然非常有用。光子的三维散射导致色球层中的冷袋在线剖面中不可见，因此它们也无法通过反转恢复。为了在这个安静的快照中成功检测到斯托克斯线性偏振，噪声水平低于 10 − 3 。 5是必要的。这旨在提高我们对色球磁场诊断的理解。为此，我们将使用 3D 模拟来研究安静太阳观测的 NLTE 反演，以量化其可靠性。我们还将研究塞曼引起的偏振的可检测性；仪器的限制和要求。目标是研究 Ca ii IR 线和反演产生实际结果的机制。
Context. 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. Aims. This study aims to establish the diagnostic capabilities of non-local thermodynamical equilibrium (NLTE) inversion techniques of Stokes profiles induced by the Zeeman e ff ect in the Ca ii λ 8542 Å line. Methods. 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 λ 8542 Å 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. Results. Our NLTE inversions applied to quiet-Sun synthetic observations provide reasonably good estimates of the chromo- spheric 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. This aims to improve our understanding of chromospheric magnetic field diagnostics. To this end we will use 3D simulations to study NLTE inversions of quiet-Sun observations to quantify their reliability. We will also study the de-tectability Zeeman-induced polarization; instrumental lim-itations and requirements. The goal is to investigate the the Ca ii IR lines and the regime which inversions yield realistic results.