High latitude E-region irregularities: New results
High latitude E-region irregularities: New results
复制标题
高纬度E区不规则现象：新结果
DOI：
10.1088/0031-8949/1987/t18/018
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发表时间：
1987
期刊：
影响因子：
2.9
通讯作者：
J. Providakes
中科院分区：
文献类型：
--
作者：
B. Fejer;J. Providakes
雷达观测表明，小尺度(几米或更小)的极光两流波的相速度仍然接近离子声速。然而，在极大等离子体期间，电子温度漂移，因此，极光电喷流区的离子声速可能由于两个强驱动流波而增强。最新的非线性理论可以解释大的反常电子加热以及两流相速度的变化。然而，观测到的与磁场垂直的角度大于几度的等离子体波仍未得到解释。雷达干涉仪测量表明，在非常活跃的时期，经常从高度局部化和动态散射区观测到强回波。在这种情况下，两个流波的相速度可超过900m/S，而梯度漂移波具有很宽的频谱，平均相速度有时大于600m/S。此外，极光雷达回波经常出现共振(即尖峰)回波，其多普勒频移与环境交叉场等离子体漂移无关。这些波与离子回旋波有关，离子回旋波是由上E区极大的场定向漂移驱动的。本文将回顾在极光E区，特别是在高度扰动期间研究米级等离子体波的最新实验结果，并讨论导致其产生和饱和的物理过程。
Radar observations have shown that the phase velocity of small scale (a few meters and smaller) auroral two stream waves remains close to the ion acoustic speed. However, during periods of very large plasma drifts the electron temperature, and consequently, the ion acoustic speed in the auroral electrojet region is enhanced possibly by strongly driven two stream waves. Recent nonlinear theories can explain the large anomalous electron heating as well as the variation of the two stream phase velocity. However, the observations of plasma waves at angles larger than a few degrees from the perpendicular to the magnetic field remain unexplained. Radar interferometer measurements show that during very active periods strong echoes are often observed from highly localized and dynamic scattering regions. On these occasions, the two stream waves have phase velocities which can exceed 900 m/s, and the gradient drift waves have very broad spectra with mean phase velocities sometimes larger than 600 m/s. Furthermore, resonant (i.e., sharply peaked) auroral radar echoes, with Doppler shifts independent of the ambient cross field plasma drift are often present near the edges of auroral arcs. These waves have been associated with ion cyclotron waves driven by very large field aligned drifts in the upper E-region. This paper will review recent experimental results on the study of meter scale plasma waves in the auroral E-region, particularly during highly disturbed periods, and will also discuss the physical processes responsible for their generation and saturation.