On Some Electric Discharges in the Atmosphere
Sakurai, T.
Abstract
A statistical investigation of some kinds of electric discharges in the atmosphere is performed, which are recorded with the aid of the induced current in the same single-turned square loop as described in the present memoir by S. Imamiti. The galvanometre used is also the same one. The main results are given as follows;
(1) Three kinds of groups are distinguished;(a), non-periodic,(b),quasi-periodic,(c),periodic variation, in which the first group has the largest number of occurrence and second follows it, the third being smallest. The group b is accompanied with cyclones and thunderstorms attacking near the observatory and frequently observed between 20 h and 4 h in local time, while c group appears only when the main part of thunderstorm passes near the observatory.
(2)The mean diurnal variation of the number of discharges with a maximum in the night is very similar with that of atmospherics already known. But considering the similar type of b and the result (1), it is likely that electric discharge of this type may be originated in not so far from the observatory.
(3) There is no distinct relation between discharge and line of discontinuity as well as rainfall, but marked discharges are increased with the former, and decreased with the latter to some extent.
(4) Distance and direction of cyclone from the observatory seems to bear clear relation to the signs of discharges, showing negative discharge(decrease of the earth's vertical magnetic field) when a cyclone is found in south-west direction to the observing station, and positive for a north-east one, while both signs appear for a south-east cyclone and north-west one.
(5) In most cases discharges proceeds rainfall about 7 or 8 hours, though there are many cases of discharge without rainfall or the latter without former.
(6) It seems that discharges are rarely accompanied with Typhoons, while they are observed for almost all cyclones.
(7) In the case of ash-fall accompanied with volcanic eruption, none of discharge is recorded.
(8) Discharges are observed five or six hours before thunders are heard. As a thunder approaches to the observatory, amplitudes of discharges become larger, and frequency of them are greatly increased. When it comes so near that ?2s(*) are observed, c type discharges begin, and amplitudes of them become very large, while occurring frequency of discharge decrease extremely.
(note from editor)
*:Thunderstorm symbol
