Parker Solar Probe In Situ Observations of Magnetic Reconnection Exhausts during Encounter 1-猫眼课题宝

DOI：

10.3847/1538-4365/ab55ee

发表时间：

2020-01

期刊：

The Astrophysical Journal Supplement Series

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通讯作者：

中科院分区：

其他

文献类型：

作者：

T. Phan;S. Bale;S. Bale;J. Eastwood;B. Lavraud;J. Drake;M. Øieroset;M. Shay;M. Pulupa;M. Stevens;R. Macdowall;A. Case;D. Larson;J. Kasper;P. Whittlesey;A. Szabo;K. Korreck;J. Bonnell;T. D. D. Wit-T.-D.-D.-Wit-144094338;K. Goetz;P. Harvey;T. Horbury;R. Livi;D. Malaspina;K. Paulson;N. Raouafi;M. Velli

电流片中的磁重联将磁能转化为粒子能。这一过程可能在靠近太阳的太阳风的加速和加热中发挥重要作用。帕克太阳探测器（PSP）的观测为研究这一问题提供了一个新的机会，因为它在前所未有的近距离测量太阳风。在第一个轨道上，PSP遇到了大量的电流片在太阳风通过近日点在35.7太阳半径。我们对这些电流表进行了全面的调查，发现了21个重联排气的证据。这些排气在日光层电流片、日冕物质抛射和常规太阳风中被观测到。然而，我们发现，在近日点附近遇到的大多数电流片，在那里磁场最强，等离子体β最低，是与爆发性径向喷流相关的Alfvénic结构，这些电流片似乎没有经历局部重联。我们研究了电流片周围的条件，以解决为什么一些电流片重新连接，而其他没有。一个关键的区别似乎是跨电流片的等离子体速度剪切的程度：21个重联排气的平均速度剪切是阿尔文速度剪切的24%，而43个阿尔文电流片的平均剪切是阿尔文速度剪切的71%。这一发现可能表明，大的，尽管是亚阿尔夫文的，速度剪切抑制重联。另一种解释是，阿尔夫维尼克电流片是孤立的旋转间断，不会发生局部重联。

Magnetic reconnection in current sheets converts magnetic energy into particle energy. The process may play an important role in the acceleration and heating of the solar wind close to the Sun. Observations from Parker Solar Probe (PSP) provide a new opportunity to study this problem, as it measures the solar wind at unprecedented close distances to the Sun. During the first orbit, PSP encountered a large number of current sheets in the solar wind through perihelion at 35.7 solar radii. We performed a comprehensive survey of these current sheets and found evidence for 21 reconnection exhausts. These exhausts were observed in heliospheric current sheets, coronal mass ejections, and regular solar wind. However, we find that the majority of current sheets encountered around perihelion, where the magnetic field was strongest and plasma β was lowest, were Alfvénic structures associated with bursty radial jets, and these current sheets did not appear to be undergoing local reconnection. We examined conditions around current sheets to address why some current sheets reconnected while others did not. A key difference appears to be the degree of plasma velocity shear across the current sheets: the median velocity shear for the 21 reconnection exhausts was 24% of the Alfvén velocity shear, whereas the median shear across 43 Alfvénic current sheets examined was 71% of the Alfvén velocity shear. This finding could suggest that large, albeit sub-Alfvénic, velocity shears suppress reconnection. An alternative interpretation is that the Alfvénic current sheets are isolated rotational discontinuities that do not undergo local reconnection.

Parker Solar Probe In Situ Observations of Magnetic Reconnection Exhausts during Encounter 1

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