Structured plasma sheet thinning observed by Galileo and 1984‐129
Structured plasma sheet thinning observed by Galileo and 1984‐129
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DOI：
10.1029/93ja02290
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发表时间：
1993-12
影响因子：
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通讯作者：
G. Reeves;R. D. Belian;T. Fritz;M. Kivelson;R. Mcentire;E. Roelof;B. Wilken;Donald J. Williams
中科院分区：
文献类型：
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作者：
G. Reeves;R. D. Belian;T. Fritz;M. Kivelson;R. Mcentire;E. Roelof;B. Wilken;Donald J. Williams
1990年12月8日，伽利略号航天器在前往木星的途中利用地球作为重力辅助。它的轨道是这样的，它在1900到2000 UT之间大约在当地午夜穿过地球同步轨道。与此同时，1984-129号航天器也在当地午夜附近定位在地球同步轨道上。当两个航天器在同一当地时间段的近地等离子体片中时，观察到了几次通量丢失事件。通量丢失事件与亚暴发展阶段近地尾部的等离子体变薄有关。这一时期的独特之处在于，伽利略提供了近地等离子体片的快速径向分布，而1984-129年则提供了方位角分布。通过这两个航天器的测量，我们可以区分空间结构和时间变化。我们的观察证实，地球同步磁通丢失事件与等离子体片变薄是一致的，等离子体片变薄使航天器的磁连接从捕获区域改变到更远的等离子体片。然而，在这一时期，稀疏发生在两个空间和时间尺度上。地球同步脱落是高度局部化的现象，持续30分钟，叠加在持续约4小时的更全面的尾部重组上。
On December 8, 1990, the Galileo spacecraft used the Earth for a gravity assist on its way to Jupiter. Its trajectory was such that it crossed geosynchronous orbit at approximately local midnight between 1900 and 2000 UT. At the same time, spacecraft 1984-129 was also located at geosynchronous orbit near local midnight. Several flux dropout events were observed when the two spacecraft were in the near-Earth plasma sheet in the same local time sector. Flux dropout events are associated with plasma sheet thinning in the near-Earth tail during the growth phase of substorms. This period is unique in that Galileo provided a rapid radial profile of the near-Earth plasma sheet while 1984-129 provided an azimuthal profile. With measurements from these two spacecraft we can distinguish between spatial structures and temporal changes. Our observations confirm that the geosynchronous flux dropout events are consistent with plasma sheet thinning which changes the spacecraft's magnetic connection from the trapping region to the more distant plasma sheet. However, for this period, thinning occurred on two spatial and temporal scales. The geosynchronous dropouts were highly localized phenomena of 30 min duration superimposed on a more global reconfiguration of the tail lasting approximately 4 hours.