Three-dimensional simulation on generation of polarization electric field in the midlatitude E-region ionosphere
Three-dimensional simulation on generation of polarization electric field in the midlatitude E-region ionosphere
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DOI：
10.1029/2003ja010238
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发表时间：
2004
影响因子：
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通讯作者：
T. Yokoyama;M. Yamamoto;S. Fukao;R. Cosgrove
中科院分区：
文献类型：
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作者：
T. Yokoyama;M. Yamamoto;S. Fukao;R. Cosgrove
[1]我们已经研究了准周期（QP）回波的产生和相关的极化电场，通过使用一个完整的三维（3-D）模拟。三维模拟有助于研究电离层等离子体的真实结构。电流闭合系统的研究是其中一个重要的问题，适合通过我们的模拟来检查。我们模拟了两种特殊的情况：（1）散在的E（Es）层包含一个等离子体云，它具有有限的纬向伸长和向南的中性风;（2）Es层有一个小的正弦扰动，并且在旋转风切变场中处于平衡高度。在情况1中，由极化电场驱动的霍尔电流在等离子体云内流动，并转变成电磁耦合E区和F区的场对准电流。另一方面，在情况2中，电流闭合主要发生在Es层本身内。我们发现F区的积分Pedersen电导率（）强烈影响E区的极化机制。在情况2中，当极化电场驱动的霍尔电流可以在Es层内闭合时，较小的极化电场会导致较大的极化电场。在情况1中，当霍尔电流应该作为场取向电流流到F区以维持极化电场时，较小的导致较小的极化电场，因为其用作霍尔电流的电阻。电场的映射也受到影响。我们的研究结果表明，E-区和F-区之间的耦合不是简单的行为，而是根据E-区条件表现出各种行为。
[1] We have studied the generation of quasi-periodic (QP) echoes and the associated polarization electric fields by using a fully three-dimensional (3-D) simulation. The 3-D simulation is helpful to investigate realistic structures of the ionospheric plasma. Study of current closure system is one of the important issues and is suitable to be checked by our simulation. We simulated two particular cases: (1) the sporadic- E (Es) layer contains a plasma cloud which has finite zonal elongation and a southward neutral wind applied; and (2) the Es layer has a small sinusoidal perturbation and is at the equilibrium altitude within a rotational wind shear field. In case 1, Hall current driven by the polarization electric field flows within the plasma cloud and turns into the field-aligned current that electromagnetically couples the E-region and the F-region. In case 2, on the other hand, current closure occurs mainly within the Es layer itself. We have found that integrated Pedersen conductivity of the F-region () strongly affects the polarization mechanism in the E-region. In case 2, when the Hall current driven by the polarization electric field can be closed within Es layers, smaller leads to larger polarization electric fields. In case 1, when the Hall current should flow as a field-aligned current to the F-region in order to sustain polarization electric fields, smaller leads to smaller polarization electric fields because serves as a resistance to the Hall current. Mapping of the electric field is also affected by . Our results suggest that coupling between the E-region and the F-region is not simply behaved but shows various behaviors depending on the E-region condition.