International Cooperative Study of ELF VLF Electromagnetic Noises

斯坦福大学ELF VLF辐射计是地球仪上的八个观测站之一，设置在高知大学理学部地球观测站。利用迄今为止获得的数据，我们进行了以下研究。1.用于分析甚低频电磁噪声波形。我们假设雷电流波形为源a，并使用快速傅里叶拉普拉斯变换方法进行了数值计算。因此，我们合理地解释了所观察到的波形.对观测到的哨声波形进行了分析，解释了其频散和振幅特征。3.并利用观测到的哨声资料研究了发生在澳大利亚北方磁共轭区的闪电特征.我们研制了ELF电磁脉冲的自动波形记录器，获得了许多有趣的波形，包括在地球电离层空腔中的基频8Hz处的一个非常高的Q值振荡。5.我们设计了宇宙线簇射射电辐射波形记录仪，并进行了实验测量。6.采用埋置于地表下的球形天线测量地电位的系统。并对城区电磁噪声进行了详细的调查。7.我们仔细地检查了极低频VLF辐射计的资料，并将它们与地震的发生联系起来，发现电磁噪声与弹性波到达观测台的时间和震源的发射时间相吻合。8.在电磁屏蔽室内，用锤子敲击岩石，得到了岩石表面的电场波形。9.最近在四国发生的地震的震中已经进行了全面的调查。

As one of the eight stations on the globe, the Stanford University ELF VLF Radiometer were set at the Earth Observatory, Faculty of Science, Kochi University. Using data obtained so far we have made the following studies. 1. For analysing VLF electromagnetic noise waveforms. we have assumed the lightning current waveform as source a and made numerical calculations using the Fast Fourie Laplace Transform method. We have thus reasonably interpreted the observed waveforms.2. We have also analysed Whistler waveforms observed and interpreted the frequency dispersion and the amplitude characteristics. 3. And we have studied lightning characteristics which occurred at the magnetic conjugate areas in the northern part of Australia using the observed whistler data.4. We have made an automatic waveform recorder of ELF electromagnetic pulses and obtained many interesting waveforms including a very high Q value oscillations at 8 Hz which is the fundamental frequency in the earth-ionosphere cavity. 5. We have designed a waveform recorder of radio emission which will be emitted from cosmic ray showers, and made a test measurement. 6. The measuring system of the earth potential using ball antennas which are set under the ground surface. and made a detailed surveys of EM noises in the urban area. 7. We have carefully checked the ELF VLF Radiometer data and correlate them with the occurrence of earthquakes and found the EM noises which coincide (1) with the elastic wave arrival at the Observatory, and (2) with the emission time at the hypocenter. 8. We have obtained the electric field waveforms emitted from the rocks hit with a hammer in the EM shielded room. 9. A comprehensive survey has been made to locate the epicenters of the earthquakes which occurred recently in Shikoku.