Electron and ion edges and the associated magnetic topology of the reconnecting magnetopause
Electron and ion edges and the associated magnetic topology of the reconnecting magnetopause
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DOI：
10.1002/2015ja021580
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发表时间：
2015-11
期刊：
影响因子：
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通讯作者：
M. Øieroset;T. Phan;J. Gosling;M. Fujimoto;V. Angelopoulos
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文献类型：
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作者：
M. Øieroset;T. Phan;J. Gosling;M. Fujimoto;V. Angelopoulos
利用高分辨率爆发模式THEMIS数据，我们详细研究了重联磁层顶的电子和离子边缘以及23个高剪切重联磁层顶交叉点的相关磁拓扑结构。电子边缘被认为是对进入磁鞘的电子和伴随的磁层电子的首次损失的最地球探测。因此，电子边缘标志着最可测量的开放（重新连接）场线。离子边缘被认为是进入磁鞘离子的最向地探测，总是在电子边缘的太阳方向或同时被探测到，这表明整个低纬度边界层（LLBL）都在开放的场线上。电子和离子边缘的径向分离是由于进入磁鞘的电子具有比进入磁鞘的离子高得多的速度，这一事实与飞行时间效应有关。重要的是，我们的研究表明，对覆盖各种磁鞘和磁层种群的整个能量范围的三维粒子分布的检查对于正确确定LLBL的磁拓扑结构是必不可少的。从有限能量范围内的电子俯仰角分布推导拓扑可能导致不正确的拓扑推导。
Using high‐resolution burst mode THEMIS data, we have examined in detail the electron and ion edges of the reconnecting magnetopause and the associated magnetic topologies of 23 high shear reconnecting magnetopause crossings. The electron edge is identified as the most earthward detection of entering magnetosheath electrons and the accompanying first loss of magnetospheric electrons. The electron edge thus marks the most earthward measurable open (reconnected) field line. The ion edge, identified as the most earthward detection of entering magnetosheath ions, was always detected either sunward of the electron edge or simultaneous with it, indicating that the entire low‐latitude boundary layer (LLBL) was on open field lines. The radial separation of the electron and ion edges is due to a time‐of‐flight effect associated with the fact that the entering magnetosheath electrons have considerably higher speeds than the entering magnetosheath ions. Importantly, our study reveals that an examination of three‐dimensional particle distributions covering the entire range of energies of the various magnetosheath and magnetospheric populations present is essential for a correct determination of the magnetic topology of the LLBL. Deducing the topology from electron pitch angle distributions covering a limited energy range can lead to incorrect deduction of the topology.