电离层阿尔芬谐振器对高频入射波的调制

The modulation of ionospheric Alfvén resonator on HF incident waves

舒曼谐振对高频波谱的调制效应作为高频入射波在电离层中传播产生的非线性效应之一 ,已经在理论和实验上都得到证明。但电离层中另一个天然谐振腔 -电离层阿尔芬谐振器 (IAR)是否对高频电磁波同样存在调制作用的问题并未得到重视。文章从波动场对电离层电子温度变化的影响出发 ,在理论上分析了IAR调制高频电磁波的可能性并讨论了IAR调制高频波的可能机制。结果表明 :阿尔芬谐振场对高频波谱的调制效应也是存在的 ;和舒曼共振场对高频信号的调制机理不同 ,IAR对高频信号的调制和阿尔芬谐振场的幅度成二次关系 ,会直接激发形成ULF波和高频信号的交叉谱并在IAR本征频率上产生一系列谱峰值 ;由于这种调制作用比较微弱以及阿尔芬波频率极低 ,从而导致ULF磁流体波对高频波的调制效果不易观测到。

The modulation of Schumann resonance on high-frequency electromagnetic waves has been proved both theoretically and experimentally. However, the same attention has not been paid to the modulation of the ionospheric Alfvén resonator on HF waves. To start with the dependence of the ionospheric electron temperature variation on the Alfvén resonant field, the possibility and potential mechanism of the modulation of the ionospheric Alfvén resonator on HF waves are analyzed in this paper. The results show that there can still exist such a modulation effect. But much different from that of Schumann resonance, the depth of modulation of IAR on HF waves is proportionate to the square of the Alfvén resonant field, which can give rise to the cross-spectrum between ULF waves and HF waves and produce spectral peaks at gyro-frequencies of IAR. For the weak interaction and the extremely low Alfvén frequency, it is usually hard to observe the cross modulation between IAR and HF waves.