Ba II D1和D2谱线的磁灵敏度
The Magnetic Sensitivity of the Ba II D1 and D2 Lines of the Fraunhofer Spectrum
摘要：
物理解释的谱线偏振产生的联合行动的汉勒和塞曼效应提供了一个独特的机会，获得经验信息的隐藏方面的太阳和恒星的磁性。为此，重要的是要实现一个完整的理解的灵敏度的出射谱线偏振的存在下的磁场。在这里，我们提出了一个详细的理论研究的作用，共振散射和磁场的Ba II的夫琅和费光谱的D1和D2线的偏振信号，分别在4934和4554。我们采用了Ba II的三能级模型，并考虑了$^{135}$ Ba和$^{137}$ Ba同位素所显示的超精细结构。尽管它们的丰度相对较小（18%），但来自这两种同位素的贡献确实是解释这些线中观察到的偏振信号的基础。我们考虑一个光学薄板模型，通过它，我们可以调查在一个严格的方式所涉及的基本物理机制（共振极化，塞曼，Paschen-Back和Hanle效应），避免由于辐射转移效应的并发症。我们假设板从下面的光球太阳连续辐射场照射，我们调查的辐射散射在90度，无论是在存在和不存在的磁场，确定性和微湍流。我们特别表明存在的差分磁灵敏度的三峰Q/I的档案中观察到的D2线在安静的区域靠近太阳的肢体，这是非常感兴趣的磁场诊断。
英文摘要：
The physical interpretation of the spectral line polarization produced by the joint action of the Hanle and Zeeman effects offers a unique opportunity to obtain empirical information about hidden aspects of solar and stellar magnetism. To this end, it is important to achieve a complete understanding of the sensitivity of the emergent spectral line polarization to the presence of a magnetic field. Here we present a detailed theoretical investigation on the role of resonance scattering and magnetic fields on the polarization signals of the Ba II D1 and D2 lines of the Fraunhofer spectrum, respectively at 4934 Å and 4554 Å. We adopt a three-level model of Ba II, and we take into account the hyperfine structure that is shown by the $^{135}$Ba and $^{137}$Ba isotopes. Despite of their relatively small abundance (18%), the contribution coming from these two isotopes is indeed fundamental for the interpretation of the polarization signals observed in these lines. We consider an optically thin slab model, through which we can investigate in a rigorous way the essential physical mechanisms involved (resonance polarization, Zeeman, Paschen-Back and Hanle effects), avoiding complications due to radiative transfer effects. We assume the slab to be illuminated from below by the photospheric solar continuum radiation field, and we investigate the radiation scattered at 90 degrees, both in the absence and in the presence of magnetic fields, deterministic and microturbulent. We show in particular the existence of a differential magnetic sensitivity of the three-peak Q/I profile that is observed in the D2 line in quiet regions close to the solar limb, which is of great interest for magnetic field diagnostics.
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