Multiscale electrodynamics of the ionosphere‐magnetosphere system
Multiscale electrodynamics of the ionosphere‐magnetosphere system
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DOI：
10.1029/2004ja010457
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发表时间：
2004-09
影响因子：
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通讯作者：
A. Streltsov;W. Lotko
中科院分区：
文献类型：
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作者：
A. Streltsov;W. Lotko
(1)本文研究了电离层和低空磁层参数如何介导极光和亚极光磁层中常见的低空卫星观测到的小尺度、强电磁结构的形成和时空特性。该研究是基于一个时间演化的非线性系统的数值模拟，该系统描述了磁层-电离层耦合系统在场向电流方面的多尺度电动力学，包括准静态和Alfvenic。模拟结果表明，即使在磁层中没有谐振腔，在120公里高度上，大尺度、缓慢演化的电流系统与弱导电电离层相互作用也能产生垂直尺寸为10-20公里的强电场和电流。当背景电离层Pedersen电导率SP较低但高于电离层上方Alfven电导率SA =1 /m0vA时，电离层电导率在大尺度上行和下行电流边界处的强梯度中形成。当SPSA时，电离层可以产生垂直尺寸小于10公里的电磁波。这些波可以被困在经典的电离层Alfven谐振腔内，并且电离层反馈不稳定性可以显著放大它们的振幅。索引项：2736磁层物理学：磁层/电离层相互作用；2704磁层物理：极光现象（2407）；2753磁层物理：数值模拟；2411电离层：电场（2712）；2437电离层：电离层动力学；关键词：磁层-电离层相互作用，电离层反馈不稳定性，场向电流，阿尔芬波
(1) In this paper we investigate how the parameters of the ionosphere and the low-altitude magnetosphere mediate the formation and spatiotemporal properties of small-scale, intense electromagnetic structures commonly observed by low-altitude satellites in the auroral and subauroral magnetosphere. The study is based on numerical modeling of a time-evolving, nonlinear system that describes multiscale electrodynamics of the magnetosphere-ionosphere coupled system in terms of field-aligned currents, both quasi- static and Alfvenic. Simulations show that intense electric fields and currents with a perpendicular size of 10-20 km at 120 km altitude can be generated by a large-scale, slowly evolving current system interacting with a weakly conducting ionosphere, even without a resonant cavity in the magnetosphere. These structures form in the strong gradient in the ionospheric conductivity that develops at the boundary between the large- scale upward and downward currents when the background ionospheric Pedersen conductivity, SP, is low but higher than the Alfven conductivity, SA =1 /m0vA, above the ionosphere. When SPSA the ionosphere can generate electromagnetic waves with perpendicular sizes less than 10 km. These waves can be trapped inside the cavity of the classical ionospheric Alfven resonator, and their amplitude can be significantly amplified there by the ionospheric feedback instability. INDEX TERMS: 2736 Magnetospheric Physics: Magnetosphere/ionosphere interactions; 2704 Magnetospheric Physics: Auroral phenomena (2407); 2753 Magnetospheric Physics: Numerical modeling; 2411 Ionosphere: Electric fields (2712); 2437 Ionosphere: Ionospheric dynamics; KEYWORDS: magnetosphere-ionosphere interaction, ionospheric feedback instability, field-aligned current, Alfven wave