Flux enhancements of field-aligned low-energy O+ ion (FALEO) in the inner magnetosphere: A possible source of warm plasma cloak and oxygen torus
Flux enhancements of field-aligned low-energy O+ ion (FALEO) in the inner magnetosphere: A possible source of warm plasma cloak and oxygen torus
复制标题
内磁层中场对准低能 O 离子 (FALEO) 的通量增强：温暖等离子体斗篷和氧环的可能来源
DOI：
10.1029/2021ja030008
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发表时间：
2022
影响因子：
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通讯作者：
and J. W. Gjerloev
中科院分区：
文献类型：
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作者：
Nose;M.;A. Matsuoka;Y. Miyoshi;K. Asamura;T. Hori;M. Teramoto;I. Shinohara;M. Hirahara;C. A. Kletzing;C. W. Smith;R. J. MacDowall;H. E. Spence;G. D. Reeves;and J. W. Gjerloev
2018年9月22日05-07 UT期间，Arase，货车艾伦探测器A和B在夜侧内磁层中同时观测到场向低能O+离子（FALEO）的通量增强。FALEO出现在磁偶极信号之后，延迟约6-20分钟。在Arase，它仅在平行于磁场的方向上具有从几keV到100 eV的能量色散特征，而在探针A和B，它在平行和反平行方向上的能量从几keV降低到10 eV。我们进行了数值模拟跟踪轨道的测试O+离子在一个模型磁层，这是从上面的电离层3-15分钟后，亚暴发射。飞行与真实的卫星具有相同轨道的虚拟卫星，我们创建了O+离子的虚拟能量-时间谱图，以与观察到的谱图进行比较。结果表明它们之间有很好的对应关系，表明FALEO起源于电离层O+离子，这些离子是在亚暴开始时从上电离层中提取的，并沿着磁场流向地磁赤道。结果还表明，在发射后3-9小时，小于400 eV的测试O ~+离子在内磁层中的空间分布与暖等离子体斗篷和氧环的空间分布相似。因此，我们得出结论，FALEO是这些冷离子的来源。
Flux enhancements of field‐aligned low‐energy O+ion (FALEO) are simultaneously observed by Arase, Van Allen Probes A and B in the nightside inner magnetosphere during 05–07 UT on September 22, 2018. FALEOs appear after a magnetic dipolarization signature with approximately 6–20 min delay. It has the energy‐dispersion signature from a few keV to ∼100 eV only in the direction parallel to the magnetic field at Arase, while it decreases its energy from a few keV down to 10 eV in both the parallel and antiparallel directions at Probes A and B. We perform a numerical simulation to trace trajectories of test O+ions in a model magnetosphere, which are launched from above the ionosphere 3–15 min after a substorm. Flying virtual satellites that have the same orbits as the real satellites, we create virtual energy‐time spectrograms of O+ions to compare with the observed ones. Results show a very good correspondence between them, indicating that FALEOs originate from ionospheric O+ions that are extracted from the upper ionosphere at substorm onset and flow along the magnetic field toward the geomagnetic equator. It is also revealed that 3–9 hr after their launch, test O+ions less than 400 eV have a spatial distribution in the inner magnetosphere which is similar to those of the warm plasma cloak and the oxygen torus. We therefore conclude that FALEO is a source of those cold ion populations.