极光区电离层中TID谱的非线性演变

本文利用欧洲非相干散射雷达数据,分析研究了极光带静日电离层行扰,得到较高F区中非线性波-波相互作用的实验证据.TID动态频谱与一维波数谱显示等离子体参量起伏（不规则性）时空尺度由长周期向短周期、由小波数向大波数演化;双谱与作用密度时变率表明有一系列连锁式非线性三波共振相互作用发生.重力波波数随高度的变化说明在较高F区出现了重力波的过反射（over-reflection）.简要讨论了引起过反射的波-流相互作用.重力波的反射及其波数的弱频散性有可能使非线性三波相互作用共振条件得以满足.

NONLINEAR EVOLUTION OF TID'S SPECTRA IN THE AURORAL IONOSPHERE

In this paper a typical event of TIDs in the quiet daytime auroral ionosphere is analyzed and some observational evidences of nonlinear wave-wave interactions in the upper F-region are obtained by using the EISCAT radar data. The dynamic frequency spectra and one dimensional wavenumber spectra of TIDs show an energy cascading from longer periods (larger scales) to shorter ones (smaller scales). The bispectra and the temporal rates of change of the action density indicate that a chain of nonlinear resonant triad interactions take place. Variation of AGW's wavenumber with height implies that an over-reflection in the upper F-region occurs, and possible wave-stream interactions giving rise to the over-reflection are discussed in brief. The weakness of the dispersion together with the reflection may enable the resonant conditions to be satisfied.