Quiet time densities of hot ions at geosynchronous orbit
Quiet time densities of hot ions at geosynchronous orbit
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DOI：
10.1029/98ja00291
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发表时间：
1998-08
影响因子：
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通讯作者：
S. Maurice;M. Thomsen;D. McComas;R. Elphic
中科院分区：
文献类型：
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作者：
S. Maurice;M. Thomsen;D. McComas;R. Elphic
在地球同步轨道上，热离子(100 eV{endash}40keV)的密度随当地时间变化。通常，密度在午夜附近最大，朝着两个终结点下降，在中午附近最小。这种对当地时间的依赖在洛斯阿拉莫斯同步等离子体数据中经常被观察到。我们使用了一个月的数据(1996年6月)和一个简单的磁层内粒子漂移模型来探索它的起源。我们首先证明了黑夜密度分布是根据漂移路径的拓扑结构形成的：囚禁轨道被耗尽，只有在开放轨道上漂移的粒子才能贡献这个群体，特别是对于在低K{subp}时间进行的观测。然后，我们突出了日侧通量中的光谱吸收，这是当粒子穿过地冕时发生的。电荷交换模型解释了在不同螺距角下，在低K{subp}下观察到的吸收信号的形状和能量范围。根据当地时间计算的密度吸收与观测值相符。因此，地球磁层中粒子运动的这些基本原理很容易解释地球同步轨道上热离子密度与当地时间的关系。[版权所有]1998美国地球物理联合会
Densities of hot (100 eV{endash}40 keV) ions vary with local time at geosynchronous orbit. Typically, the density is maximum near midnight, falls off toward both terminators, and is minimum near noon. This local time dependence is routinely observed in the Los Alamos geosynchronous plasma data. We use a month of these data (June 1996) and a simple model of particle drifts within the magnetosphere to explore its origins. We first show that the nightside density profile is shaped according to the drift path topology: trapped orbits are depleted, and only particles drifting on open trajectories contribute to this population, particularly for observations taken at times of low K{sub p}. Then, we highlight spectral absorption in dayside fluxes, which occurs when the particles pass through the geocorona. A model of charge exchange accounts for the shape and energy range of the absorption signatures observed at low K{sub p} for varying pitch angles. The density absorption computed versus local time matches the observations. Hence these basic principles of particle motion in the terrestrial magnetosphere readily explain the local time dependence of the hot ion density at geosynchronous orbit. {copyright} 1998 American Geophysical Union