Flux Rope Merging and the Structure of Switchbacks in the Solar Wind
Flux Rope Merging and the Structure of Switchbacks in the Solar Wind
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DOI：
10.3847/1538-4357/ac4016
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
O. Agapitov;J. Drake;M. Swisdak;S. Bale;T. Horbury;J. Kasper;R. Macdowall;F. Mozer;T. Phan;M. Pulupa;N. Raouafi;M. Velli
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文献类型：
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作者：
O. Agapitov;J. Drake;M. Swisdak;S. Bale;T. Horbury;J. Kasper;R. Macdowall;F. Mozer;T. Phan;M. Pulupa;N. Raouafi;M. Velli
帕克太阳探测器（PSP）的一项重大发现是，径向太阳风速度存在大量局部增加，以及与之相关的磁场急剧偏转--之字形（SB）。SBs的一个可能产生机制是通过太阳表面附近的开放和闭合磁通量之间的磁重联，称为交换重联，导致通量绳（FR）喷射到太阳风中。观察还表明，SB进行合并，符合FR图片这些结构。通过直接观测、解析分析和数值模拟，探讨了FR合并在控制太阳风中SBs结构中的作用。解析分析揭示了FR结构的关键特征及其与日心距离R的比例关系，这些特征与观测结果一致，并表明合并在控制SB结构中的关键作用。FR合并示出大力有利于减少的强度的包裹磁场和延伸的SB。另一个结果是SB内的轴向磁场的主导，这导致在SB边界处观察到的磁场沿轴向方向的特征性急剧旋转。最后，FR模式中SB区域的径向尺度表明SB识别的观测概率对R不敏感，这与PSP SB观测的最新统计分析一致。
A major discovery of Parker Solar Probe (PSP) was the presence of large numbers of localized increases in the radial solar wind speed and associated sharp deflections of the magnetic field—switchbacks (SBs). A possible generation mechanism of SBs is through magnetic reconnection between open and closed magnetic flux near the solar surface, termed interchange reconnection, that leads to the ejection of flux ropes (FRs) into the solar wind. Observations also suggest that SBs undergo merging, consistent with an FR picture of these structures. The role of FR merging in controlling the structure of SBs in the solar wind is explored through direct observations, analytic analysis, and numerical simulations. Analytic analysis reveals key features of the structure of FRs and their scaling with heliocentric distance R, which are consistent with observations and demonstrate the critical role of merging in controlling the structure of SBs. FR merging is shown to energetically favor reductions in the strength of the wrapping magnetic field and the elongation of SBs. A further consequence is the resulting dominance of the axial magnetic field within SBs that leads to the observed characteristic sharp rotation of the magnetic field into the axial direction at the SB boundary. Finally, the radial scaling of the SB area in the FR model suggests that the observational probability of SB identification should be insensitive to R, which is consistent with the most recent statistical analysis of SB observations from PSP.