Theory of Magnetic Switchbacks Fully Supported by Parker Solar Probe Observations

IF 4.8 2区 物理与天体物理 Q1 ASTRONOMY & ASTROPHYSICS Astrophysical Journal Pub Date : 2023-11-01 DOI:10.3847/1538-4357/acfd91
Gabor Toth, Marco Velli, Bart van der Holst
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Abstract

Abstract Magnetic switchbacks are rapid high-amplitude reversals of the radial magnetic field in the solar wind that do not involve a heliospheric current sheet crossing. First seen sporadically in the 1970s in Mariner and Helios data, switchbacks were later observed by the Ulysses spacecraft beyond 1 au and have been recently discovered to be a typical component of solar wind fluctuations in the inner heliosphere by the Parker Solar Probe spacecraft. While switchbacks are now well understood to be spherically polarized Alfvén waves thanks to Parker Solar Probe observations, their formation has been an intriguing and unsolved puzzle. Here we provide a simple yet predictive theory for the formation of these magnetic reversals: the switchbacks are produced by the distortion and twisting of circularly polarized Alfvén waves by a transversely varying radial wave propagation velocity. We provide an analytic expression for the magnetic field variation, establish the necessary and sufficient conditions for the formation of switchbacks, and show that the proposed mechanism works in a realistic solar wind scenario. We also show that the theoretical predictions are in excellent agreement with observations, and the high-amplitude radial oscillations are strongly correlated with the shear of the wave propagation speed. The correlation coefficient is around 0.3–0.5 for both encounter 1 and encounter 12. The probability of this being a lucky coincidence is essentially zero with p -values below 0.1%.
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帕克太阳探测器观测完全支持磁转换理论
磁反转是太阳风中径向磁场的快速高振幅反转,不涉及日球层电流片的交叉。在20世纪70年代的水手号和太阳神号的数据中首次发现了这种现象,后来尤利西斯号在1au以外的地方观测到了这种现象,最近帕克号太阳探测器发现这是太阳风内部日球层波动的典型组成部分。虽然由于帕克太阳探测器的观测,现在已经很好地理解了回转波是球极化的阿尔夫萨芬波,但它们的形成一直是一个有趣的未解之谜。在这里,我们为这些磁反转的形成提供了一个简单而又可预测的理论:磁反转是由圆极化alfvsamn波在横向变化的径向波传播速度下的扭曲和扭曲产生的。我们给出了磁场变化的解析表达式,建立了转换形成的充分必要条件,并证明了所提出的机制在现实的太阳风场景下是有效的。我们还表明,理论预测与观测结果非常吻合,高振幅径向振荡与波传播速度的剪切密切相关。遭遇1和遭遇12的相关系数都在0.3-0.5左右。当p值低于0.1%时,这种幸运巧合的概率基本上为零。
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来源期刊
Astrophysical Journal
Astrophysical Journal 地学天文-天文与天体物理
CiteScore
8.40
自引率
30.60%
发文量
2854
审稿时长
1 months
期刊介绍: The Astrophysical Journal is the foremost research journal in the world devoted to recent developments, discoveries, and theories in astronomy and astrophysics.
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