The role of the equatorial electrojet in the evening ionosphere
The role of the equatorial electrojet in the evening ionosphere
复制标题
DOI：
10.1029/91ja02227
复制
发表时间：
1992-02
影响因子：
--
通讯作者：
G. Haerendel;J. Eccles
中科院分区：
文献类型：
--
作者：
G. Haerendel;J. Eccles
本文着重讨论赤道E区在夜间电离层电动力学中的作用。本文用场线积分的一维电动力学模型研究了日落时赤道电离层中的电喷流的影响和反应。一维的，随时间变化的模型预测的水平电场的一个给定的时间变化的赤道电射流的水平电流的发散。在晚上，水平电流的负发散提供了一个净向上的电流，从赤道E区进入赤道高海拔（和相当纬度）的电离层。这种向上的电流影响垂直电场的大小和随后的上覆电离层的水平等离子体漂移。该模型允许的假设下，沿沿着场线的电离密度的分布是成比例的化学平衡分布的电射流区域内的电离的化学重组和动态再分配。东向水平电场和日落后2小时内的净上升电流联合收割机共同将电离带抬出E区，导致电离密度低于平衡值。随着电离密度（电导率）的降低，赤道电离层的电动力学也发生了变化。这个模型的赤道电射流电流发散可以作为一个较低的边界，全球性的，二维模型的赤道电场。最后，提出了赤道电射流电流在日落附近有一个显着的作用，在确定的postsunset增强的水平电场。电喷射区域提供了最好的途径，电流被引导从向阳面，以满足垂直电流需求的F区域中性风力发电机日落后。由于电离和等离子体抬升的复合，E区的电导率降低，增强了水平（向东）电场，从而增加了抬升的速度。因此，电离的动态调整具有不稳定的，反馈的电场，这可以解释夜间变化的水平电场增强的关系。
This paper focuses on the role of the equatorial E region in the electrodynamics of the evening ionosphere. The influence and reaction of the electrojet current on the equatorial ionosphere at sunset is investigated using a field line integrated, one-dimensional, electrodynamic model. The one-dimensional, time-varying model predicts the divergence of the horizontal current of the equatorial electrojet for a given time variation of the horizontal electric field. The negative divergence of the horizontal current during the evening hours provides a net upward current out of the equatorial E region into the integrated ionosphere of higher equatorial altitudes (and equivalent latitudes). This upward current affects the vertical electric field magnitudes and subsequent horizontal plasma drifts of the overlying ionosphere. The model allows for chemical recombination and dynamic redistribution of ionization within the electrojet region under the assumption that the profile of the ionization density along a field line is proportional to the chemical equilibrium profile. The eastward horizontal electric field and the net upward current during the 2 hours after sunset combine to lift the ionization out of the E region resulting in ionization densities less than the equilibrium values. As the ionization densities (conductivities) are reduced, the electrodynamics of the equatorial ionosphere is altered. This model of the equatorial electrojet current divergence can be used as a lower boundary to global, two-dimensional models of the equatorial electric fields. Finally, it is proposed that the equatorial electrojet current near sunset has a significant role in the determination of the postsunset enhancement of the horizontal electric field. The electrojet region provides the best avenue for current to be channeled from the dayside to meet the vertical current demands of the F region neutral wind dynamo after sunset. The conductivity reduction in the E region due to the recombination of ionization and the plasma uplift enhances the horizontal (eastward) electric field and thereby increases the speed of the uplift. Thus the dynamic adjustment of ionization has an unstable, feedback relationship with the electric fields which may explain the night to night variability of the horizontal electric field enhancement.