This review describes observations of the polar magnetic fields, models for the cyclical formation and decay of these fields, and evidence of their great influence in the solar atmosphere. The polar field distribution dominates the global structure of the corona over most of the solar cycle, supplies the bulk of the interplanetary magnetic field via the polar coronal holes, and is believed to provide the seed for the creation of the activity cycle that follows. A broad observational knowledge and theoretical understanding of the polar fields is therefore an essential step towards a global view of solar and heliospheric magnetic fields. Analyses of both high-resolution and long-term synoptic observations of the polar fields are summarized. Models of global flux transport are reviewed, from the initial phenomenological and kinematic models of Babcock and Leighton to present-day attempts to produce time-dependent maps of the surface magnetic field and to explain polar field variations, including the weakness of the cycle 23 polar fields. The relevance of the polar fields to solar physics extends far beyond the surface layers from which the magnetic field measurements usually derive. As well as discussing the polar fields’ role in the interior as seed fields for new solar cycles, the review follows their influence outward to the corona and heliosphere. The global coronal magnetic structure is determined by the surface magnetic flux distribution, and is dominated on large scales by the polar fields. We discuss the observed effects of the polar fields on the coronal hole structure, and the solar wind and ejections that travel through the atmosphere. The review concludes by identifying gaps in our knowledge, and by pointing out possible future sources of improved observational information and theoretical understanding of these fields.

这篇综述描述了极地磁场的观测、这些磁场的周期性形成和衰变的模型，以及它们对太阳大气的巨大影响的证据。在太阳周期的大部分时间里，极场分布主导着日冕的整体结构，通过极地冕洞提供了大部分行星际磁场，并被认为为随后的活动周期的产生提供了种子。因此，对极地场的广泛观测知识和理论理解是迈向太阳和日光层磁场全球视野的重要一步。总结了对极地场的高分辨率和长期天气观测的分析。回顾了全球磁通输运模型，从巴布科克和莱顿最初的现象学和运动学模型，到当今试图生成表面磁场随时间变化的图并解释极场变化，包括 23 极周期的弱点字段。极场与太阳物理学的相关性远远超出了磁场测量通常源自的表面层。除了讨论极地场在内部作为新太阳周期种子场的作用外，本文还跟踪了它们对日冕和日光层的影响。全球日冕磁结构由表面磁通量分布决定，并在大尺度上受极场支配。我们讨论了观测到的极地场对冕洞结构以及穿过大气层的太阳风和喷射的影响。审查的结论是确定了我们知识中的差距，并指出了未来改进这些领域的观测信息和理论理解的可能来源。