Observations of Closed Magnetic Flux Embedded in the Lobes During Periods of Northward IMF
Observations of Closed Magnetic Flux Embedded in the Lobes During Periods of Northward IMF
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DOI：
10.1029/2021ja029281
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发表时间：
2020-10
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影响因子：
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通讯作者：
L. J. Fryer;R. Fear;J. Coxon;I. Gingell
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文献类型：
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作者：
L. J. Fryer;R. Fear;J. Coxon;I. Gingell
磁层的高纬度、波瓣区域通常被认为含有冷的、低能量的等离子体群。然而，在向北的行星际磁场期间，偶尔会观察到高能等离子体群。我们列举了三个例子，当星团观测到叶中不典型的“热”等离子体群时。对于这三个事件中的两个，我们给出了双星观测到的等离子体片的同步观测结果。叶中的等离子体与等离子体片之间的相似性表明，在高纬度产生等离子体的机制可能是尾部重联，导致中午至午夜子午线附近的闭合通量被困住。从磁层顶成像仪到极光全球探测成像仪和DMSP/特殊传感器紫外线光谱成像仪的补充图像显示，在至少一个半球的每个事件中形成的跨极弧线在所有三个事件中都与集群航天器的足迹直接相交。星系团足迹与跨极弧的交集与叶中高能等离子体群的观测同步。这进一步支持了这样的结论，即在磁层高纬度叶区域观察到的高能等离子体很可能位于封闭的场线上。
The high latitude, lobe regions of the magnetosphere are often assumed to contain cool, low energy plasma populations. However, during periods of northward Interplanetary Magnetic Field, energetic plasma populations have occasionally been observed. We present three cases when Cluster observed uncharacteristically “hot” plasma populations in the lobe. For two of the three events, we present simultaneous observations of the plasma sheet observed by Double Star. The similarity between the plasma in the lobe and the plasma sheet suggests that the mechanism that produces plasma at high latitudes is likely to be tail reconnection, resulting in a trapped “wedge” of closed flux about the noon‐midnight meridian. Complementary images from Imager for Magnetopause to Aurora Global Exploration and DMSP/Special Sensor Ultraviolet Spectrographic Imager show that transpolar arcs, which form in each event in at least one hemisphere, directly intersect the footprint of the Cluster spacecraft in all three events. The intersection of the Cluster footprint with the transpolar arcs is synchronous with the observation of the energetic plasma populations in the lobe. This further supports the conclusion that it is likely this energetic plasma observed in the high latitude lobe regions of magnetosphere is on closed field lines.