Study of Plasma Turbulence by Means of Bispectrum Anaylyses

利用ISIS-2号卫星对Siple站VLF发射机信号的观测和Aureol-3号卫星对Alpha VLF信号的观测，对空间等离子体中的非线性波-波相互作用进行了实验研究。我们成功地分析了大量的数据，其结果可以概括如下：（1）对Siple信号的分析表明，我们可以探测到ISIS-2卫星上的边带结构，这是Tanaka，Hayakawa等人首先观测到的。（1987年）。双谱分析表明，这些边带是由于VLF发射信号与电离层中原有的ELF辐射之间的非线性耦合引起的，进一步分析Aureol-3卫星Alpha VLF发射数据，得到了更多的证据，证明了这种非线性耦合引起的边带结构。定向测量表明，这种相互作用发生在电磁强VLF信号和准静电ELF发射之间。边带波也被发现是准静电的，这可以通过这样的边带仅在电天线上被检测到的事实来证实。

The experimental study on the nonlinear wave-wave interactions in the space plasma was carried out by using both the ISIS-2 satellite observations of Siple Station VLF transmitter signals and the Aureol-3 satellite observations of Alpha VLF signals. We suceeded in analysing extremely a lot of data, and the results can be summarised as follows :(1)The analysis of Siple signals has indicated that we could detect the sideband structures on the ISIS-2 satellite, as was first observed by Tanaka, Hayakawa et al.(1987). Then the bispectrum analysis indicated that these sidebands are due to the nonlinear coupling between VLF transmitter signal and the pre-existing ELF emission in the ionosphere.The further analyzes of Aureol-3 satellite data of Alpha VLF transmission, has yielded some more evidence of the detection of sideband structures due to the monlinear interaction. The direction finding measurement has suggested that this interaction takes place between an electromagnetic strong VLF signal and a quasi-electrostatic ELF emission. The sideband wave is also found to be quasi-electrostatic, which can be confirmed by the fact that such sidebands are only detected on electric antennas.