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arXiv 1609.05723astro-ph.SR
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在一般Hanle-Zeeman区域中部分频率重分布的共振线极化的转移

The transfer of resonance line polarization with partial frequency redistribution in the general Hanle-Zeeman regime

Ernest Alsina Ballester, Luca Belluzzi, Javier Trujillo Bueno

摘要:

谱线偏振编码了大量关于太阳大气的热和磁性质的信息。然而,从理论和计算的角度来看,模拟强共振线的斯托克斯轮廓是一个复杂的问题,特别是当需要考虑部分频率再分布(PRD)效应时。在这项工作中,我们考虑一个二能级原子的存在下的磁场的任意强度(Hanle-Zeeman制度)和取向,确定性和微结构。在严格的PRD理论方法的框架内工作,我们已经开发了一个数值代码,解决了完整的非LTE辐射转移问题的偏振辐射,在一维模型的太阳大气,占汉勒和塞曼效应的联合作用,以及PRD现象。在简要讨论了相关方程后,我们描述了问题的迭代求解方法和我们已经开发和实现的数值工具。最后,我们提出了一些说明性的应用程序,形成在不同的高度在太阳大气中的两个共振线,并提供了一个详细的物理解释的计算斯托克斯配置文件。我们发现,在强共振线PRD效应敏感的斯托克斯矢量传输方程的磁光项产生显着的U/I翼信号,以及一个非常有趣的磁灵敏度在翼的线偏振剖面。我们还表明,弱场近似必须谨慎使用时,考虑PRD效应。

英文摘要:

The spectral line polarization encodes a wealth of information about the thermal and magnetic properties of the solar atmosphere. Modeling the Stokes profiles of strong resonance lines is, however, a complex problem both from the theoretical and computational point of view, especially when partial frequency redistribution (PRD) effects need to be taken into account. In this work, we consider a two-level atom in the presence of magnetic fields of arbitrary intensity (Hanle-Zeeman regime) and orientation, both deterministic and micro-structured. Working within the framework of a rigorous PRD theoretical approach, we have developed a numerical code which solves the full non-LTE radiative transfer problem for polarized radiation, in one-dimensional models of the solar atmosphere, accounting for the combined action of the Hanle and Zeeman effects, as well as for PRD phenomena. After briefly discussing the relevant equations, we describe the iterative method of solution of the problem and the numerical tools that we have developed and implemented. We finally present some illustrative applications to two resonance lines that form at different heights in the solar atmosphere, and provide a detailed physical interpretation of the calculated Stokes profiles. We find that in strong resonance lines sensitive to PRD effects the magneto-optical terms of the Stokes-vector transfer equation produce conspicuous U/I wing signals along with a very interesting magnetic sensitivity in the wings of the linear polarization profiles. We also show that the weak-field approximation has to be used with caution when PRD effects are considered.

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