The Electric Charge neutralized by the Lightning Discharge

[摘要] The electricity of the thunderstorm was observed by various facilities during the summers of 1940 to 1944, in the neighbourhood of Maebashi, Gumma Prefecture, where the top occurrence of thunderstorms in Japan is recorded. The report(1) of the observations in the summers of 1940 and 1941, was already published. In this paper the author intends to report the electric charge neutralized by the lightning discharge and the distance of the consecutive discharge in the thunder-cloud.In the observation in three summers from 1942 to 1944, we investigated twenty four thunderstorms. We took 171 simultaneous observations of sudden changes of the electric field at three places and 543 simultaneous observations at two places. The general tendency of the results of the analysis was nearly the same as in the summers of 1940 and 1941. The following results were obtained by the detailed analysis of the observation data.(1) The electric charge neutralized by a lightning discharge is large and generally more than 100 coulombs and seldom reaches 300-400 coulombs when the thunderstorm is developing.(2) The electric charge neutralized is small and generally less than 40-60 coulombs, and most numerous in the region less than 10 coulombs when the thunderstorm is decaying.(3) The electric charge neutralized is medium when the thundercloud is moving and stationary in the electrical activity. And it is also perceived that the electric charge neutralized is greater in the front-side of the thundercloud and smaller in the rear-side of it.(4) These facts may be due to the ending of the generation of electrified water drops and to the increase of the electrical conductivity of the air in the clouds.(5) The distance between the discharging spots is large in the developing stage of the thunderstorm and smaller in the decaying stage. And the distance becomes longer as the electric charge neutralized by a lightning discharge becomes greater. The distance is about 1km when the electric charge is 10-20coulombs, 2-3km when the charge is 100coulombs, and more than 4km when the charge is 300coulombs.(6) The rather large negative change of the electric field somewhat frequently occurs in eighteen thunderstorms out of twenty four storms examined. These negative changes occur in the decaying stage of the thunderstorm. This may perhaps be due to the horizontal lightning discharge.

[学科分类] 大气科学