The Structure and Origin of Switchbacks: Parker Solar Probe Observations
The Structure and Origin of Switchbacks: Parker Solar Probe Observations
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DOI：
10.3847/1538-4357/acd17e
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发表时间：
2023-01
期刊：
影响因子：
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通讯作者：
Jia Huang;J. Kasper;L. Fisk;D. Larson;Michael T. McManus;C. H. Chen;Mihailo M. Martinovi'c;K. Klein;Luke Thomas;Mingzhe Liu;B. Maruca;Lingling Zhao;Yu Chen;Q. Hu;L. Jian;J. Verniero;M. Velli;R. Livi;P. Whittlesey;A. Rahmati;O. Romeo;T. Niembro;K. Paulson;M. Stevens;A. Case;M. Pulupa;S. Bale;J. Halekas
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作者：
Jia Huang;J. Kasper;L. Fisk;D. Larson;Michael T. McManus;C. H. Chen;Mihailo M. Martinovi'c;K. Klein;Luke Thomas;Mingzhe Liu;B. Maruca;Lingling Zhao;Yu Chen;Q. Hu;L. Jian;J. Verniero;M. Velli;R. Livi;P. Whittlesey;A. Rahmati;O. Romeo;T. Niembro;K. Paulson;M. Stevens;A. Case;M. Pulupa;S. Bale;J. Halekas
回转是指磁场迅速逆转，持续时间从几秒钟到几小时。目前的帕克太阳探测器（PSP）的观测提出了许多关于之字形的性质悬而未决的问题。例如，当它们通过内日球层传播时，它们是稳定的吗？它们是如何形成的？在这项工作中，我们的目标是调查的结构和起源之字形。为了研究之字形的稳定性，我们假设其中的小尺度电流片是由磁编织产生的，它们应该起稳定之字形的作用。在七次遭遇中，PSP观测发现了1000多个之字形，我们发现内部的电流片比外部的之字形多得多，这表明这些微结构应该能够稳定S形结构的之字形。此外，我们还研究了氦的变化，以追踪它们的起源。我们发现在之字形的富氦和贫氦的人口，这意味着之字形可能起源于太阳的封闭和开放的磁场区域。此外，我们观察到，α-质子的微分速度也表现出复杂的变化相比，本地阿尔文速度。这两个参数的联合分布表明，低氦丰度与低差速一起是切换的主导状态。在之字形沿着氦特征的小规模电流片的存在与之字形可能通过交换重连过程起源于太阳的假设是一致的。然而，不排除其他形成机制。
Switchbacks are rapid magnetic field reversals that last from seconds to hours. Current Parker Solar Probe (PSP) observations pose many open questions in regard to the nature of switchbacks. For example, are they stable as they propagate through the inner heliosphere, and how are they formed? In this work, we aim to investigate the structure and origin of switchbacks. In order to study the stability of switchbacks, we suppose the small-scale current sheets therein are generated by magnetic braiding, and they should work to stabilize the switchbacks. With more than 1000 switchbacks identified with PSP observations in seven encounters, we find many more current sheets inside than outside switchbacks, indicating that these microstructures should work to stabilize the S-shape structures of switchbacks. Additionally, we study the helium variations to trace the switchbacks to their origins. We find both helium-rich and helium-poor populations in switchbacks, implying that the switchbacks could originate from both closed and open magnetic field regions in the Sun. Moreover, we observe that the alpha-proton differential speeds also show complex variations as compared to the local Alfvén speed. The joint distributions of both parameters show that low helium abundance together with low differential speed is the dominant state in switchbacks. The presence of small-scale current sheets in switchbacks along with the helium features are in line with the hypothesis that switchbacks could originate from the Sun via interchange reconnection process. However, other formation mechanisms are not excluded.