Abstract
It is necessary for the study of lightning discharge to observe its effects simultaneously by as various means as possible. To investigate electromagnetic effects of lightning discharge and electrical structure of thundercloud, the authors have constructed several apparata for the joint observation of thunderstorms, e. g., the lightning counter, the electrostatic fluxmeter and the atmospheric wave-form recorder for nearby thunderstorm. The record of lightning counter informs us of the average activity of nearby thunderstorms; and by the simultaneous recording of the lightning by using both the electrostatic fluxmeter and the wave-form recorder, we can accurately deliniate field-change caused by the discharge, which often has extraordinary complex character i.e., the duration of which reaches nearly 1 sec., and yet which involves rapid field-changes of the order of 10-5sec.
As the results of the thunderstorm observation held in Aug. 1953 at Maebasi-city, the following conclusion can be pointed out as for the cloud flashes in the dissipating stage of thunderstorm:
1. Effective advance velocity of supposed dipole charges in the cloud in the course of the cloud discharge is found to be very slow, i.e. of the order of 10-6cm/sec.
2. The slow cloud discharge is accompanied by the small discontinuous differential type pulses of radiation field character, which can be surmised to result from the small but rapid discontinuous discharges in the course of the same slow cloud discharge.
