The magnetic field is the main driver of the activity in the solar upper atmosphere, but its measurement is notoriously difficult. In order to determine the magnetic field in the chromosphere, transition region, and corona, we need to measure and interpret the polarization signals that the scattering of anisotropic radiation and the Hanle and Zeeman effects introduce in the emitted spectral line radiation. A number of recent advances have activated the development of this research field. ▪ The quantum theory of the generation and transfer of polarized radiation allows us to explain the polarization signals observed in chromospheric and coronal lines and to make successful predictions in unexplored spectral regions. ▪ The development of diagnostic techniques for the solar upper atmosphere has served to improve our empirical knowledge of the magnetic field in a variety of plasma structures, as well as to pave the way for their application to the unprecedented data that the new generation of solar telescopes are expected to provide. However, further improvements are required. ▪ The CLASP suborbital experiments have opened a new diagnostic window, namely ultraviolet (UV) spectropolarimetry as a tool for probing the magnetism and geometry of the upper chromosphere and transition region. A space telescope equipped with a UV spectropolarimeter would lead to major advances in our empirical understanding of solar magnetism.

中文翻译：

---

太阳高层大气中的磁场诊断


磁场是太阳高层大气活动的主要驱动因素，但众所周知，它的测量非常困难。为了确定色球层、过渡区和日冕中的磁场，我们需要测量和解释各向异性辐射的散射以及 Hanle 和 Zeeman 效应在发射的光谱线辐射中引入的极化信号。最近的一些进展激活了这一研究领域的发展。▪ 极化辐射产生和转移的量子理论使我们能够解释在色球层和日冕线中观察到的极化信号，并在未探索的光谱区域中做出成功的预测。▪ 太阳高层大气诊断技术的发展有助于提高我们对各种等离子体结构中磁场的经验知识，并为它们应用于新一代太阳望远镜有望提供的前所未有的数据铺平了道路。但是，还需要进一步改进。▪ CLASP 亚轨道实验打开了一个新的诊断窗口，即紫外 （UV） 光谱偏振法作为探测上色层和过渡区的磁性和几何形状的工具。配备紫外光谱偏振仪的太空望远镜将导致我们对太阳磁场的实证理解取得重大进展。