Imaging radar observations and nonlocal theory of large-scale plasma waves in the equatorial electrojet
Imaging radar observations and nonlocal theory of large-scale plasma waves in the equatorial electrojet
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赤道电喷射大尺度等离子体波的成像雷达观测与非局域理论
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
J. Chau
中科院分区：
文献类型：
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作者：
D. Hysell;J. Chau
抽象的。利用Jicamara相干散射雷达资料，对赤道电喷流昼夜大尺度(L~1公里)波进行了研究。雷达主波束内等离子体不规则性的图像是用多基线干涉法形成的。根据非局部梯度漂移不稳定性理论对这些图像进行了分析，并与Ronchi等人最近进行的非线性计算机模拟进行了比较。(1991)和Hu和Bhattacharjee(1999)。在白天，大尺度海浪呈现一种非定常的动力平衡状态，其特征是剪切波和扩散波的应变和破坏，然后是自发再生，正如Ronchi等人预测的那样。(1991年)。在夜间，当陡峭的等离子体密度梯度出现时，缓慢传播的大尺度垂直延伸波占主导地位。Eikonal分析表明，这些波是被捕获的(绝对不稳定的)或几乎被捕获的(对流不稳定的)，并且能够在局部不稳定的海拔区域之间隧道。中尺度波主要是瞬变的(对流稳定的)，但在由背景密度分布确定的狭窄海拔范围内可能变得绝对不稳定。这些特征与Hu和Bhattacharjee(1999)提出的模拟结果基本一致。一类新的大尺度主波在黄昏时沿着从高海拔向西和向下扫过E区的带发生。关键词。电离层(赤道电离层；电离层不规则性；等离子体波和不稳定性)
Abstract. Large-scale ( l ~ 1 km) waves in the daytime and night-time equatorial electrojet are studied using coherent scatter radar data from Jicamarca. Images of plasma irregularities within the main beam of the radar are formed using interferometry with multiple baselines. These images are analyzed according to nonlocal gradient drift instability theory and are also compared to nonlinear computer simulations carried out recently by Ronchi et al. (1991) and Hu and Bhattacharjee (1999). In the daytime, the large-scale waves assume a non-steady dynamical equilibrium state characterized by the straining and destruction of the waves by shear and diffusion followed by spontaneous regeneration as predicted by Ronchi et al. (1991). At night, when steep plasma density gradients emerge, slowly propagating large-scale vertically extended waves predominate. Eikonal analysis suggests that these waves are trapped (absolutely unstable) or are nearly trapped (convectively unstable) and are able to tunnel between altitude regions which are locally unstable. Intermediate-scale waves are mainly transient (convectively stable) but can become absolutely unstable in narrow altitude bands determined by the background density profile. These characteristics are mainly consistent with the simulations presented by Hu and Bhattacharjee (1999). A new class of large-scale primary waves is found to occur along bands that sweep westward and downward from high altitudes through the E-region at twilight. Key words. Ionosphere (equatorial ionosphere; ionospheric irregularities; plasma waves and instabilities)