Observational astrophysics started when spectroscopy could be applied to astronomy. Similarly, observational work on stellar magnetic fields became possible with the application of spectro-polarimetry. In recent decades there have been dramatic advances in the observational tools for spectro-polarimetry. The four Stokes parameters that provide a complete representation of partially polarized light can now be simultaneously imaged with megapixel array detectors with high polarimetric precision (10−5 in the degree of polarization). This has led to new insights about the nature and properties of the magnetic field, and has helped pave the way for the use of the Hanle effect as a diagnostic tool beside the Zeeman effect. The magnetic structuring continues on scales orders of magnitudes smaller than the resolved ones, but various types of spectro-polarimetric signatures can be identified, which let us determine the field strengths and angular distributions of the field vectors in the spatially unresolved domain. Here we review the observational properties of the magnetic field, from the global patterns to the smallest scales at the magnetic diffusion limit, and relate them to the global and local dynamos.

中文翻译：

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斯托克斯极化法揭示的太阳磁场

当光谱学可以应用于天文学时，观测天体物理学就开始了。同样，随着光谱极化法的应用，对恒星磁场的观测工作成为可能。近几十年来，光谱偏振测量的观测工具取得了巨大的进步。提供部分偏振光的完整表示的四个斯托克斯参数现在可以使用具有高偏振精度（偏振度为 10-5）的百万像素阵列检测器同时成像。这导致人们对磁场的性质和特性有了新的认识，并为将汉勒效应用作塞曼效应之外的诊断工具铺平了道路。磁性结构在比解析的小几个数量级的尺度上继续，但是可以识别各种类型的光谱偏振特征，这让我们可以确定空间未解析域中场矢量的场强和角分布。在这里，我们回顾了磁场的观测特性，从全局模式到磁扩散极限的最小尺度，并将它们与全局和局部发电机联系起来。