Strugarek Antoine, Belucz Bernadett, Brun Allan Sacha, Dikpati Mausumi, Guerrero Gustavo
Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France.
Solar Physics and Space Plasma Research Center, School of Mathematics and Statistics, University of Sheffield, Sheffield, S3 7RH UK.
Space Sci Rev. 2023;219(8):87. doi: 10.1007/s11214-023-01027-0. Epub 2023 Dec 14.
The solar tachocline is an internal region of the Sun possessing strong radial and latitudinal shears straddling the base of the convective envelope. Based on helioseismic inversions, the tachocline is known to be thin (less than 5% of the solar radius). Since the first theory of the solar tachocline in 1992, this thinness has not ceased to puzzle solar physicists. In this review, we lay out the grounds of our understanding of this fascinating region of the solar interior. We detail the various physical mechanisms at stake in the solar tachocline, and put a particular focus on the mechanisms that have been proposed to explain its thinness. We also examine the full range of MHD processes including waves and instabilities that are likely to occur in the tachocline, as well as their possible connection with active region patterns observed at the surface. We reflect on the most recent findings for each of them, and highlight the physical understanding that is still missing and that would allow the research community to understand, in a generic sense, how the solar tachocline and stellar tachocline are formed, are sustained, and evolve on secular timescales.
太阳较差自转层是太阳内部的一个区域，位于对流包层底部，存在强烈的径向和纬向切变。基于日震反演，已知较差自转层很薄（小于太阳半径的5%）。自1992年提出第一个太阳较差自转层理论以来，其薄度一直困扰着太阳物理学家。在这篇综述中，我们阐述了对太阳内部这个迷人区域的理解依据。我们详细介绍了太阳较差自转层中涉及的各种物理机制，并特别关注那些为解释其薄度而提出的机制。我们还研究了磁流体动力学（MHD）过程的全貌，包括可能在较差自转层中发生的波和不稳定性，以及它们与在太阳表面观测到的活动区模式的可能联系。我们思考了其中每一项的最新发现，并强调了仍欠缺的物理理解，这些理解将使研究界能够从一般意义上理解太阳较差自转层和恒星较差自转层是如何形成、维持以及在长期时间尺度上演变的。
