甚低频（VLF）谱图显示

代码说明：

Very Low Frequency (VLF) spectrograms show sometimes sets of lines called MLR (Magnetospheric Line Radiation) with frequency spacing close to 50 or 60 Hz. It is very tempting to attribute these MLR to Power Line Harmonic Radiation (PLHR). PLHR are the ELF and VLF waves radiated by electric power systems at the harmonic frequencies of 50 or 60 Hz. Here we show for the first time large scale MLR observed simultaneously on ground and on board a low altitude satellite which is flying over the same zone.