Modeling of inner plasma sheet and ring current during substorms
Modeling of inner plasma sheet and ring current during substorms
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DOI：
10.1029/1999ja900014
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发表时间：
1999-07-01
影响因子：
2.8
通讯作者：
Delcourt, DC
中科院分区：
文献类型：
--
作者：
Fok, MC;Moore, TE;Delcourt, DC
模拟了亚暴极化过程中内部等离子体片和环电流的演变。根据 Tsyganenko 89 模型，通过拉伸和极化磁层来处理亚暴周期。为了阐明稳定对流和感应电场对环流发展的相对影响，将感应电场叠加在两个基线对流状态上：使用弱电场的非风暴状态和使用较强电场的风暴时状态。使用我们的单粒子代码在时间上向后追踪粒子轨迹到假定具有稳定特性的源区域，获得了这两个亚暴期间 12 个地球半径 (RE) 的夜面离子分布。这些边界离子随后加速并传输到内部磁层中，通过我们的环电流动力学模型进行建模。该模拟生成了许多经常观察到的亚暴注入特征，包括在明确定义的“注入边界”尾部突然出现热等离子体、“注入前沿”的向地运动、该增强区域的方位角和尾部扩展，以及在地球同步轨道附近创建特征离子色散模式。非风暴和风暴情况的比较表明，在没有对流增强的情况下发生的亚暴主要产生交叉尾流的增强，但环流的变化很小。在强对流的情况下，亚暴的作用是使对流增强，在内磁层中产生强大的环流。
The evolution of the inner plasma sheet and the ring current during substorm dipolarizations is simulated. A substorm cycle is treated by stretching and dipolarizing the magnetosphere according to the Tsyganenko 89 model. In order to clarify the relative influences of steady convection and induction electric field on ring current development, the inductive electric field is superposed on two baseline convective states: a nonstorm state using a weak electric field, and a storm-time state using a stronger electric field, Ion distributions on the nightside at 12 Earth radii (RE) during these two substorms are obtained using our single-particle code to trace particle trajectories backward in time to source regions assumed to have steady characteristics. The subsequent acceleration and transport of these boundary ions into the inner magnetosphere is modeled by our kinetic model of the ring current. The simulation generates many frequently observed features of substorm injections, including the sudden appearance of hot plasma tailward of a sharply defined "injection boundary," the earthward motion of an "injection front" the azimuthal and tailward expansion of this enhanced region, and the creation of characteristic ion dispersion patterns near geosynchronous orbit. Comparison of the nonstorm and storm cases suggests that substorms occurring without a convection enhancement produce mainly an enhancement of the cross-tail current but little change in the ring current. With strong convection, the role of substorms is to enable the convection enhancement to create robust ring current in the inner magnetosphere.