Observation of lightning current in the soil by rocket-triggered lightning

In recent years, there has been a significant increase in the damage to electrical and electronic devices owing to lightning surge-induced overvoltage/overcurrent, in Japan. In particular, the lightning surge overcurrent that flows through grounding lines can cause serious damage to electronic equipment. To understand the phenomenon of the lightning surge current propagation in the ground poles, it is important to understand the lightning current propagation in the soil. We have developed a detection circuit for determining the lightning current distribution in the soil and have measured the lightning current caused by rocket-triggered lightning in the soil. We have observed the lightning current in the soil owing to a negative precursor discharge at a depth of 0.1 m, 30 m from the triggered flash point.