Average magnetotail electron and proton pitch angle distributions from Cluster PEACE and CIS observations
Average magnetotail electron and proton pitch angle distributions from Cluster PEACE and CIS observations
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DOI：
10.1029/2011gl046770
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发表时间：
2011-03
影响因子：
5.2
通讯作者：
A. Walsh;C. Owen;A. Fazakerley;C. Forsyth;I. Dandouras
中科院分区：
文献类型：
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作者：
A. Walsh;C. Owen;A. Fazakerley;C. Forsyth;I. Dandouras
我们提出的结果，从第一次系统调查的质子和电子俯仰角分布的磁尾，根据集群CIS和PEACE数据合并的质子等离子体β（βp）。质子分布符合磁尾离子的规范图像-由向地流动和双向场对准粒子组成的边界层，与最近对时变小束的观察一致，当βp ≥ 3时，它让位于广泛各向同性的中心等离子体片。电子分布与正则图像有很大的不同。观察到由双向场对准电子组成的“边界层”，βp值高达17。这个边界很快让位给靠近中性层的垂直主导电子。因此，我们的结果表明，平均而言，没有扩展的，各向同性的电子等离子体片，质子等离子体片是不经常遇到，直到比通常假设的更高的βp。
We present results from the first systematic survey of proton and electron pitch angle distributions in the magnetotail, based on Cluster CIS and PEACE data binned by proton plasma β (βp). The proton distributions conform to the canonical picture of magnetotail ions ‐ a boundary layer made up of Earthward streaming and bidirectional field‐aligned particles, consistent with recent observations of time‐varying beamlets, which gives way to a broadly isotropic central plasma sheet when βp ∼ 3. The electron distributions are significantly different from the canonical picture. A “boundary layer” made up of bidirectional field‐aligned electrons is observed to values of βp as high as 17. This boundary quickly gives way to perpendicular‐dominated electrons close to the neutral sheet. Hence, our results suggest that, on average, there is no extended, isotropic electron plasma sheet and that the proton plasma sheet is not routinely encountered until higher βp than commonly assumed.