发表机构
Istituto ricerche solari Aldo e Cele Daccò (IRSOL), Faculty of Informatics, Università della Svizzera italiana; Euler Institute, Faculty of Informatics, Università della Svizzera italiana（瑞士意大利大学信息学院阿尔多和切莱达科太阳研究所; 瑞士意大利大学信息学院欧拉研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究评估了CRD极限在Sr I 4607 Å谱线散射偏振建模中的有效性，发现除弱偏振信号外CRD均适用，PRD效应仅在信号低于0.3%时显著。
AI 中文摘要
背景。Sr I 4607 Å谱线中的散射偏振是诊断太阳宁静光球中不可解析的小尺度磁场的关键工具，这些磁场无法通过基于塞曼效应的技术探测。完全频率重分布（CRD）极限通常用于对该谱线进行建模，但其有效性及对磁敏感性的影响尚未得到系统研究。鉴于新设施以前所未有的精度观测该谱线，以及未来针对长期宁静太阳磁场的巡天计划，这一研究具有及时性。目的。我们评估CRD极限相对于Sr I 4607 Å偏振散射的一般部分频率重分布（PRD）描述，重点关注其通过汉勒效应产生的磁敏感性。方法。我们在半经验一维平面平行静态大气中，针对与汉勒诊断相关的磁场构型，求解了CRD和PRD散射下偏振辐射的非局部热动平衡辐射转移问题。结果。对于小尺度不可解析磁场，其中场仅通过Q/I的汉勒去极化起作用，CRD和PRD的出射轮廓及汉勒敏感性基本一致。对于确定性磁场，当偏振信号超过约0.3%时，CRD仍然准确；对于较弱的信号，PRD效应可能显著影响出射轮廓。结论。在绝大多数观测相关情况下，CRD足以对Sr I 4607 Å散射偏振进行建模；PRD效应仅在弱偏振信号时重要。
英文摘要
Context. Scattering polarization in the Sr I 4607 Å line is a key diagnostic for small-scale, unresolved magnetic fields in the quiet solar photosphere, inaccessible to Zeeman-based techniques. The complete frequency redistribution (CRD) limit is commonly used to model this line, but its validity and impact on magnetic sensitivity have not been systematically investigated. This is timely given new facilities observing this line with unprecedented accuracy, and future synoptic programs targeting long-term quiet-Sun magnetism. Aims. We assess the CRD limit against the general partial frequency redistribution (PRD) description of scattering for the Sr I 4607 Å polarization, focusing on its magnetic sensitivity via the Hanle effect. Methods. We solved the non-LTE radiative transfer problem for polarized radiation in a semi-empirical 1D plane-parallel static atmosphere, with CRD and PRD scattering, across magnetic field configurations relevant for Hanle diagnostics. Results. For small-scale unresolved fields, where the field acts only via Hanle depolarization of Q/I, CRD and PRD emergent profiles and Hanle sensitivity are essentially identical. For deterministic fields, CRD remains accurate when polarization signals exceed about 0.3%; for weaker signals, PRD effects can appreciably affect the emergent profiles. Conclusions. CRD is adequate for modeling Sr I 4607 Å scattering polarization in the vast majority of observationally relevant cases; PRD effects matter only for weak polarization signals.
