Simultaneous entry of oxygen ions originating from the Sun and Earth into the inner magnetosphere during magnetic storms
Simultaneous entry of oxygen ions originating from the Sun and Earth into the inner magnetosphere during magnetic storms
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DOI：
10.1029/2009ja014120
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发表时间：
2009-05-28
影响因子：
2.8
通讯作者：
Zurbuchen, T. H.
中科院分区：
文献类型：
--
作者：
Ebihara, Y.;Kasahara, S.;Zurbuchen, T. H.
本文的目的是首次提出磁暴期间内磁层中低电荷态和高电荷态氧离子几乎同时增强的现象。低电荷态O离子的风暴时间增强是公认的，但高电荷态O离子的行为却鲜为人知。ACE、Geotail和Polar卫星同时收集的数据表明：(1)在磁暴（Polar）早期，在内磁层（L = 3-5），高电荷态O离子的数量密度增加。(2)在太阳风（ACE）和近地磁尾（Geotail）中观测到的O离子数量密度没有相应的增强。(3)近地磁尾中存在的高电荷态O离子的数量密度明显低于太阳风和内磁层。我们计算了O6+离子在电场和磁场模型下的运动轨迹。在极区能量窗中观测到的O6+离子是在对流电场较强时从高纬度磁层顶向内磁层输送的。当对流电场较弱时，离子向远尾反射。无论对流电场的强度如何，在地尾能量窗口中观测到的O6+离子都被充分地从低纬度磁层顶输送到近地磁尾。根据不同入口点的对流电场，离子输运路径可以充分解释观测事实。
The aim of this paper is to present, for the first time, almost simultaneous enhancements of both low- and high-charge-state oxygen ions in the inner magnetosphere during magnetic storms. Storm-time enhancements of low- charge-state O ions are well recognized, but the behavior of high-charge-state O ions is less known. Data simultaneously collected from the ACE, Geotail, and Polar satellites indicate the following: (1) In the inner magnetosphere (at L = 3-5), the number density of high-charge-state O ions was increased during the early phase of magnetic storms (Polar). (2) No corresponding enhancements were identified in the number density of O ions observed in the solar wind (ACE) and the near-Earth magnetotail (Geotail). (3) The number density of high-charge-state O ions present in the near-Earth magnetotail was considerably lower than in the solar wind and the inner magnetosphere. We calculated trajectories of O6+ ions under electric and magnetic field models. The O6+ ions that became observable in the energy window of Polar were transported from the high-latitude magnetopause to the inner magnetosphere when the convection electric field was strong. When the convection electric field was weak, the ions were reflected toward the distant tail. The O6+ ions that became observable in the energy window of Geotail were sufficiently transported from the low- latitude magnetopause to the near-Earth magnetotail regardless of the strength of the convection electric field. The observational facts may be adequately explained in terms of ion transport paths depending on the convection electric field with different entry points.