Sub-Alfvenic Solar Wind observed by PSP: Characterization of Turbulence, Anisotropy, Intermittency, and Switchback
R. Bandyopadhyay, W. H. Matthaeus, D. J. McComas, R. Chhiber, A. V. Usmanov, J. Huang, R. Livi, D. E. Larson, J. C. Kasper, A. W. Case, M. Stevens, P. Whittlese… 展开作者
R. Bandyopadhyay, W. H. Matthaeus, D. J. McComas, R. Chhiber, A. V. Usmanov, J. Huang, R. Livi, D. E. Larson, J. C. Kasper, A. W. Case, M. Stevens, P. Whittlesey, O. M. Romeo, S. D. Bale, J. W. Bonnell, T. Dudok de Wit, K. Goetz, P. R. Harvey, R. J. MacDowall, D. M. Malaspina, M. Pulupa
In the lower solar coronal regions where the magnetic field is dominant, the Alfven speed is much higher than the wind speed. In contrast, the near-Earth solar wind is strongly super-Alfvenic, i.e., the wind speed greatly exceeds the Alfven speed. The transition between these regimes is classically described as the "Alfven point" but may in fact occur in a distributed Alfven critical region. NASA's Parker Solar Probe (PSP) mission has entered this region, as it follows a series of orbits that gradually approach more closely to the sun. During its 8th and 9th solar encounters, at a distance of 16 solar radii from the Sun, PSP sampled four extended periods in which the solar wind speed was measured to be smaller than the local Alfven speed. These are the first in-situ detections of sub-Alfvenic solar wind in the inner heliosphere by PSP. Here we explore properties of these samples of sub-Alfvenic solar wind, which may provide important previews of the physical processes operating at lower altitude. Specifically, we characterize the turbulence, anisotropy, intermittency, and directional switchback properties of these sub-Alfvenic winds and contrast these with the neighboring super-Alfvenic periods.
Generation and Expansion-Driven Growth of Switchbacks in the Outer Solar Corona and Solar Wind
Imperial College London（帝国理工学院）；University of California, Los Angeles（加州大学洛杉矶分校）；Auburn University（奥本大学）；Space Sciences Laboratory, University of California, Berkeley（加州大学伯克利分校空间科学实验室）；Istituto per la Scienza e Tecnologia dei Plasmi (ISTP), Consiglio Nazionale delle Ricerche（等离子体科学与技术研究所，意大利国家研究委员会）；The University of Texas at Austin（德克萨斯大学奥斯汀分校）
Possible Evolution of Minifilament-Eruption-Produced Solar Coronal Jets, Jetlets, and Spicules, into Magnetic-Twist-Wave "Switchbacks" Observed by the Parker Solar Probe (PSP)
Features of magnetic field switchbacks in relation to the local-field geometry of large-amplitude Alfvénic oscillations: \emph{Wind} and \emph{PSP} observations
Turbulence characteristics of switchbacks and non-switchbacks intervals observed by \emph{Parker Solar Probe}
我们使用\emph{Parker Solar Probe}（\emph{PSP}）的现场测量，以分析太阳风湍流的特征，在第一次太阳相遇期间覆盖径向距离之间的$35.7R_\odot$和$41.7R_\odot$。在我们的分析中，我们将所谓的之字形（SB）间隔（折叠磁场线）与非之字形（NSB）间隔（主要遵循帕克螺旋场）隔离开来。使用一种基于条件关联函数的技术，我们分别在SB和NSB间隔中估计了Elsasser、磁场和体速度场的功率谱。通过对两种间隔的湍流能谱的比较，我们发现了以下特点：1）后向传播Elsasser场$z^-$的去相关长度在NSB间隔中比在SB间隔中大;（2）SB层段的磁功率谱比NSB层段陡，谱指数接近-5/3，其具有接近-3/2的光谱指数; 3）SB和NSB湍流都是不平衡的，NSB具有最大的交叉螺旋度，4）SB间隔中的剩余能量大于NSB，以及5）所分析的波动由在\emph{sunward}中传播的Alfvénic波动主导（\emph{anti-sunward}）方向，用于SB（NSB）湍流。这些观察到的特征提供了进一步的证据，证明\emph{PSP}观察到的之字形与折叠磁场线有关，从而深入了解其湍流性质。
Analysis of the distribution, rotation and scale characteristics of solar wind switchbacks: comparison between the first and second encounters of Parker Solar Probe
Magnetic switchback formation: a review of proposed mechanisms
Durham University（杜伦大学）；University of Otago（奥塔哥大学）；CNRS, Instituto de Astrofísica de Canarias（法国国家科学研究中心，加那利天体物理学研究所）；Sorbonne Université, École polytechnique, Institut Polytechnique de Paris, Université Paris Saclay, Observatoire de Paris-PSL, CNRS, Laboratoire de Physique des Plasmas（索邦大学，巴黎综合理工学院，巴黎理工学院，巴黎萨克雷大学，巴黎天文台-PSL，法国国家科学研究中心，等离子体物理实验室）；SSL, University of California Berkeley（空间科学实验室，加州大学伯克利分校）；University of Maryland（马里兰大学）；Starion Group S.A.（星团集团）；Bartol Research Institute and Department of Physics and Astronomy, University of Delaware（巴托尔研究所和物理与天文系，特拉华大学）；Imperial College London（帝国理工学院）；Mahidol University（玛希隆大学）
Conversion Layer Controls the Evolution of Magnetic Deflections Near the Alfven Surface
University of Michigan（密歇根大学）；University of Delaware（特拉华大学）；Center for Astrophysics, Harvard & Smithsonian（哈佛-史密森尼天体物理中心）；University of Alabama Huntsville（阿拉巴马大学亨茨维尔分校）；Auburn University（奥本大学）；University of California Berkeley Space Sciences Laboratory（加州大学伯克利分校空间科学实验室）
Properties of Magnetic Switchbacks in the Near-Sun Solar Wind
Center for Astrophysics, Harvard & Smithsonian（哈佛-史密森天体物理中心）；Institut de Recherche en Astrophysique et Planétologie, CNES, CNRS, Université de Toulouse（天体物理学与行星学研究所，法国国家空间研究中心，法国国家科学研究中心，图卢兹大学）；Department of Physics, Imperial College London（帝国理工学院物理系）；Space Sciences Laboratory, University of California, Berkeley（加州大学伯克利分校空间科学实验室）；Astronomy and Space Physics Department, National Taras Shevchenko University of Kyiv（基辅塔拉斯舍甫琴科国立大学天文与空间物理系）；Department of Climate and Space Sciences and Engineering, University of Michigan（密歇根大学气候与空间科学与工程系）；LPC2E, OSUC, Univ Orleans, CNRS, CNES（奥尔良大学地球与环境过程实验室，观测与研究宇宙学与气候系统观测站，法国国家科学研究中心，法国国家空间研究中心）；International Space Science Institute（国际空间科学研究所）
Averaging Effects on the Solar Wind Alfven Mach Number: Implications for Switchbacks and Alfven Transition
University of Delaware（特拉华大学）；Princeton University（普林斯顿大学）；University of California, Berkeley（加州大学伯克利分校）；Mahidol University（玛希隆大学）；University of Orléans（奥尔良大学）；Kasetsart University（泰国农业大学）；NASA Goddard Space Flight Center（美国宇航局戈达德太空飞行中心）
Anisotropy of Solar-Wind Turbulence in the Inner Heliosphere at Kinetic Scales: PSP Observations
太阳风湍流的各向异性是理解日球层尺度间能量传递和场与粒子间能量转换物理的关键问题。使用\emph{Parker Solar Probe}（\emph{PSP}）的测量，我们提出了一个观察的各向异性在动力学尺度上的缓慢，Alfvénic，太阳风的内日球层。\textbf{The magnetic compressibility behaves as expected for kinetic Alfvénic turbulence below the ion scale.}一个陡峭的过渡范围之间的惯性和动力学范围内的所有方向相对于当地的背景磁场方向。发现$k_\perp \gg k_\parallel$的各向异性在过渡区和动力学区都很明显，动力学区的幂次各向异性$P_\perp/P_\parallel > 10$大于过渡区的幂次各向异性，且比1 au的幂次各向异性强.光谱指数在过渡范围内从$α_{t\parallel}=-5.7\pm 1.0$到$α_{t\perp}=-3.7\pm 0.3$变化，在动力学范围内从$α_{k\parallel}=-3.12\pm 0.22$到$α_{k\perp}=-2.57\pm 0.09$变化。相应的波矢各向异性在过渡范围内具有$k_\parallel \sim k_\perp^{0.71\pm 0.17}$的标度，并且在动力学范围内变为$k_\p…
