Abstract
The relaxation time of exponential recovery of the electric field after lightning flash occur-ring at the distance beyond 10 km is discussed. The relaxation time decreases with increasing distance, but the values obtained in the present study are found to be about 1.5 to 2 times larger than the values obtained by other workers. For close flashes, the field recoveries show almost linear change with time, which is apparently different from that for distant flashes. It is found that there is a good correlation between the average recovery rate and the occurence frequency of flashes for two storms and that the field recovery rate positively correlates with the regeneration rate of charges in thunderclouds. Hence, it is possible to estimate the regeneration rate of charges in thunderclouds from the counting of the occurrence frequency of flashes for any flash distance. The regeneration rate after lightning flash is found to be about 1-10 coul/sec for the two storms.
