Energetic particle injections to geostationary orbit: Relationship to flow bursts and magnetospheric state
Energetic particle injections to geostationary orbit: Relationship to flow bursts and magnetospheric state
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DOI：
10.1029/2012ja017773
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发表时间：
2012-10
影响因子：
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通讯作者：
V. Sergeev;I. Chernyaev;S. Dubyagin;Y. Miyashita;V. Angelopoulos;P. Boakes;R. Nakamura;M. Henderson
中科院分区：
文献类型：
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作者：
V. Sergeev;I. Chernyaev;S. Dubyagin;Y. Miyashita;V. Angelopoulos;P. Boakes;R. Nakamura;M. Henderson
[1]为了解决的机制和因素控制注入高能粒子的地球静止轨道（GEO），我们分析了外观的注入在GEO漂移壳层的情况下，检测到的流动爆发和相关的瞬态偶极的LANL航天器观测到的内磁层的入口处，在高β等离子体片区域的夜面之间的8和13 Re。我们分析了两个不同的数据集，一个包括1995-2005年的地尾观测，另一个包括2008-2009年的亚暴期间事件和大尺度相互作用的时间历史（THEMIS）观测。我们发现，只有一小部分在8-13 Re的所有流爆发与粒子注入在GEO，但这些注入相关的流有较小的值的等离子体管熵参数（PV 5/3），以及较大的变化的磁场南北分量（dBz）。这证实了内磁层（8-13 Re）入口处的爆发流穿透地球同步轨道并在那里产生高能粒子通量增加的假设。根据磁尾等离子体流的气泡理论，等离子体深穿透的概率关键取决于磁层位形的拉伸程度，并且这种依赖性在大型数据库中被统计证实是控制GEO注入发生的主要因素。我们建议使用背景等离子体管的熵值在夜侧部分的GEO漂移壳作为一个合适的参数来预测粒子注入到GEO的概率。这项研究的另一个结果是，高能粒子注入不能可靠地作为一种工具，以确定亚暴开始的时间，因为已经在许多过去的研究。
[1] To address the mechanism and factors controlling the injection of energetic particles to the geostationary orbit (GEO), we analyzed the appearance of injections at the GEO drift shell as observed by LANL spacecraft in the cases where the flow bursts and associated transient dipolarization were detected at the entry to the inner magnetosphere, in the high beta plasma sheet region on the nightside between 8 and 13 Re. We analyzed two different data sets, one including Geotail observations in 1995–2005 and another including a set of Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations in 2008–2009. We found that only a small portion of all flow bursts at 8–13 Re were associated with particle injection at GEO but that those injection-associated flows had smaller values of plasma tube entropy parameter (PV5/3) as well as larger change of magnetic field north-south component (dBz). This confirms a scenario that the bursty flows at the entry of the inner magnetosphere (8–13 Re) penetrate into GEO and produce there the energetic particles flux increase. According to the bubble theory of magnetotail plasma flows, the probability of the deep plasma penetration critically depends on how stretched the magnetospheric configuration is, and this dependence is statistically confirmed in a large database to be the major factor controlling the occurrence of GEO injections. We suggest using the background plasma tube entropy value in the nightside part of the GEO drift shell as a suitable parameter to predict the probability of particle injection to GEO. One more outcome of this study is that the energetic particle injections cannot reliably serve as a tool to identify the substorm onset times, as has been done in many past studies.