On Some Kind of Electric Discharges in the Atmosphere

Abstract

At the Kakioka magnetic observatory induction current in a single turned horizontal circuit caused by changes of the vertical magnetic field of the earth is recorded continuously. The area of the circuit is 1×10³ square meters, and in it a galvanometer is connected in series. Traces, which were considered to be due to some kind of electric discharges in the atmosphere, were often recorded on the sensitised paper. In this note the statistical investigation of those records was made. The main results are as follows:
(1) Three kinds of groups are distinguished; (a) non-periodic, (b) quasi-periodic, (c) periodic variation. The first group has the largest number of occurrence and the second follows it, the third being smallest. The group b is accompanied with cyclones and thunderstorms attacking near the observatory and frequently observed between 20h and 4h in local time, while group c appears only when the main part of thunderstorm passes near the observatory.
(2) The mean diurnal variation of the number of discharges, having a maximum in the night, is quite similar to that of atmospherics. But considering the similar type of b and the result (1), it is likely that electric discharge of this type originates 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 increase with the former, and decrease with the latter to some extent.
(4) The distance and direction of the cyclone from the observatory seem to bear close relation to the sign of discharges. The negative discharge (decrease of the earth's vertical magnetic field) is more numerous when a cyclone is found in the southwest direction of the observing station, and the positive in the north-east direction, while both signs appear when the cyclone is in the south-east and north-west direction.
(5) In most cases discharges precede rainfall about 7 or 8 hours, though there are many cases of discharge without rainfall or the latter without the 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 beared. As the 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 the frequency of occurrence of discharge decreases extremely.