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arXiv 2109.04016astro-ph.SRphysics.plasm-phphysics.space-ph
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磁通量绳合并与太阳风中switchback的结构

Flux rope merging and the structure of switchbacks in the solar wind

O. Agapitov, J. F. Drake, M. Swisdak, S. D. Bale, T. S. Horbury, J. C. Kasper, R. J. MacDowall, F. S. Mozer, T. D. Phan, M. Pulupa, N. E. Raouafi, M. Velli

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21 pages, 9 figures
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AI总结：

本文通过观测、解析和模拟探讨磁通量绳合并对太阳风中switchback结构的控制作用，揭示合并驱动其拉长与轴向磁场主导，并解释了观测概率不随日心距离变化的统计特征。

摘要：

Parker Solar Probe (PSP) 的一项重大发现是存在大量径向太阳风速度的局部增加以及相关的磁场急剧偏转现象——switchbacks (SB)。SB 的一种可能产生机制是通过太阳表面附近的开放与闭合磁通量之间的磁重联，即所谓的 interchange reconnection，这会导致磁通量绳 (FR) 被抛射进入太阳风。观测还表明 SB 会经历合并过程，这与这些结构的 FR 图景相符。本文通过直接观测、解析分析和数值模拟，探讨了 FR 合并在控制太阳风中 SB 结构方面的作用。解析分析揭示了 FR 结构的关键特征及其随日心距离 R 的标度关系，这些结果与观测相符，并揭示了合并在控制 SB 结构中的关键作用。研究表明，FR 合并在能量上是有利的，它能减弱包裹磁场的强度，并驱动观测到的 SB 拉长现象。进一步的后果是 SB 内部轴向磁场占据主导地位，导致在 SB 边界处磁场向轴向方向发生特征性的急剧旋转，这在观测中得到了揭示。最后，在 SB 的 FR 模型中，SB 面积的径向标度表明 SB 识别的观测概率应对 R 不敏感，这与 PSP 对 SB 观测的最新统计分析结果一致。

英文摘要：

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 (SB). 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 (FR) into the solar wind. Observations also suggest that SBs undergo merging, consistent with a FR picture of these structures. The role of FRs merging in controlling the structure of SB in the solar wind is explored through direct observations, through analytic analysis, and numerical simulations. Analytic analysis reveals key features of the structure of FR and their scaling with the heliocentric distance R that are consistent with observations and that reveal the critical role of merging in controlling the SB structure. FR merging is shown to be energetically favorable to reduce the strength of the wrapping magnetic field and drive the observed elongation of SBs. A further consequence is the resulting dominance of the axial magnetic field within SBs that leads to the characteristic sharp rotation of the magnetic field into the axial direction at the SB boundary that is revealed in observations. Finally, the radial scaling of the SB area in the FR model of SBs 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.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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