Mechanisms underlying the prereversal enhancement of the vertical plasma drift in the low-latitude ionosphere
Mechanisms underlying the prereversal enhancement of the vertical plasma drift in the low-latitude ionosphere
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DOI：
10.1002/2014ja020664
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发表时间：
2015-06-01
影响因子：
2.8
通讯作者：
Schunk, R. W.
中科院分区：
文献类型：
--
作者：
Eccles, J. V.;St Maurice, J. P.;Schunk, R. W.
等离子体垂直漂移的夜间反转前增强（PRE）对Appleton密度异常和夜间电离层的稳定性有重要影响。使用简化的模拟来回顾PRE起源的三种相互竞争的理论，探索它们的相对重要性，并确定它们的相互依赖性。PRE的产生和气候学所涉及的机制是，第一，一个无卷曲的电场响应与夜间F区发电机相关的垂直电场的快速变化;第二，霍尔电流在E区远离磁赤道的发散;和，第三，在赤道E区的大考林电导率的调节作用。模拟表明，赤道考林电导率创建一个重要的电流路径，限制其他两个机制之前，赤道日落和释放后，赤道日落。当终止线和磁子午线部分由于F区纬向风加速而对齐时，无旋机制是主导机制。当太阳终止点与磁子午线不一致时，这三种机制的相互作用会影响PRE的大小和时间。最后，当无卷曲机制占主导地位时，与霍尔电流机制占主导地位时相比，PRE的高度分布随高度衰减得更快。
The evening prereversal enhancement (PRE) of the vertical plasma drift has important consequences for the Appleton density anomaly and the stability of the nighttime ionosphere. Simplified simulations were used to review the three competing theories of the PRE origin, to explore their relative importance, and to indentify their interdependence. The mechanisms involved in the generation and climatology of the PRE are, first, a curl-free electric field response to rapid changes in the vertical electric field associated with the nighttime F region dynamo; second, a divergence of Hall currents in the E region away from the magnetic equator; and, third, the moderating effect of the large Cowling conductivities in the equatorial E region. The simulations indicate that the equatorial Cowling conductivity creates an important current path that limits the other two mechanisms prior to equatorial sunset and releases them after equatorial sunset. The curl-free mechanism is the dominant mechanism when the terminator and magnetic meridian are aligned in part due to the accelerating F region zonal wind. When the solar terminator is not aligned with the magnetic meridian, there is an interaction involving all three mechanisms contributing to the magnitude and timing of the PRE. Finally, the altitude profile of the PRE decays more quickly with altitude when the curl-free mechanism dominates as compared to when the Hall current mechanism dominates.