Title 多地点落雷について
Author(s) 高木, 渡辺, 有馬, 伊藤, 河崎, 仲野, 竹内, 木下, 鈴木, 斎川
Journal 電気学会論文誌B, 111, 1, 93-98 (1991)
Abstract Characteristics of lightning flashes with multiple strikes to the ground within 1s are investigated, based on the data of video pictures of lightning channels and the electric field changes. In winter, the occurrence frequency of lightning flashes with multiple strikes to the ground is 55% which is roughly twice as large as that in summer. The number of strike points in winter is also larger than that in summer. The largest number of strike points is 17 in winter, whereas 4 in summer. The polyphase fault on a power transmission line in winter might be caused by a lightning flash of this type. The average time intervals between strokes are less than 17 ms (one TV field) in winter and 90 ms in summer respectively. The average distance between strike points are 1.3 km in winter and 1.9 km in summer.

Title 雷放電路は,フラクタルであるか?
Author(s) 勝野, 河崎, 松浦
Journal 電気学会論文誌A, 111, 5, 496-497 (1991)

Title レーザー誘雷
Author(s) 藤原, 井澤, 河崎, 松浦, 山中
Journal レーザー研究, 19, 6, 528-537 (1991)
Abstract Electrical discharge guided by a 100J/2GW pulse CO2 laser is reviewed. A long air breakdown plasma channel is produced by using a Multi-Active CHannel (MACH) focusing mirror which has two focal lengths. The plasma channel has been used to guide electrical discharge over a distance of 6m in laboratory air at an applied potential of - 1.2MV. A successive plasma channel produced by the laser is more effective for discharge guiding than the chains of break plasma beads. A stepped leader was observed with a streak camera for laser guided discharge. The mean propagation velocity of the stepped leader was 105-106 m/s.

Title 電磁界変化とUHF放射からみたロケット誘雷
Author(s) 金尾, 河崎, 松浦, 山本, 堀井, 仲野, 中村, 竹内
Journal 電気学会論文誌B, 111, 10, 1079-1084 (1991)
Abstract The electric field changes, the magnetic field changes, and UHF radiations were observed during the rocket-triggered lightning experiment using the 4 channels transient memory of its sampling frequency of 1 MHz. The sensors were a flat disk antenna, a loop antenna, and a disk corn antenna respectively. Concerning the initiation of the electric and magnetic field changes, a remarkable discrepancy between the rocket-triggered lightning to the tower and the one to the ground is noticed. That is, the former is initiated by a bipolar pulse of a large amplitude. On the other hand, the amplitude of the latter increases gradually. Preceding such kind of changes, UHF isolated pulses were also recorded. The statistics of the UHF isolated pulses are presented.

Title 冬季の送電線鉄塔へのトリガード落雷に伴う磁界変化
Author(s) 山本, 相木, 松原, 松浦, 河崎, 木下, 有馬, 竹内, 藤本
Journal 電気学会論文誌B, 112, 12, 1101-1109 (1992)
Abstract The magnetic field changes due to cloud-to-ground strokes have been measured by loop antennas, which have been installed in the north-south direction and the east-west direction, respectively, in winter and summer seasons during 982 through 1989. In consequence of the measurements, it is found that there is difference between the magnetic field change due to summer lightning and that due to winter lightning, that is, the magnetic field change measured by the N-S loop antenna is the same as the magnetic field change measured by the E-W loop antenna in summer lightning, but not the same in winter lightning (Winter lightning in this paper is the triggered lightning initiated at the top of a steel tower of a transmission line.). It is considered that the difference between the magnetic field change measured by the N-S loop antenna and that by the E-W loop antenna in winter lightning is caused by the anomalous shape of the lightning channel, such as the large tortuosity of the channel close to the ground. The effects of the tortuosity of the channel on the magnetic field change is shown by the numerical analysis of magnetic field change due to the lightning stroke current, which propagates along the tortuous channel. When the lightning stroke current is estimated from the magnetic field change, it should be noted that the shape of the channel has an important effect on the magnetic field change.

Title 雷放電に伴う電界変化の時間同期多地点観測
Author(s) 牛尾, 王, 河崎, 松浦, 山本
Journal 電気学会論文誌B, 114, 11, 1160-1167 (1994)
Abstract Exploiting GPS systems, we synchronized three wideband (0.1Hz-2MHz) show antennas with the time accuracy of 1オs. With this slow antenna system, we recorded many lightning flashes at Hokuriku district area from December 2, 1993 to January 28, 1994. Almost all lightning flashes show consecutive pulses superimposing on their slow field changes with the time intervals of tens microseconds. We analyzed the arrival time difference of the pulses to different stations and succeeded in locating the sources of the pulses which are from PB (Preliminary Breakdown), L (Leader), R (Return stroke), and C (Continuing current) stage for a positive cloud to ground discharge, and from recoil streamers for a cloud discharge. Since we combine the functions of traditional slow antennas with lightning location method, this paper would provide a significant tool to study lightning physics, especially the physics of the initiation of lightning.

Title 冬季雷放電開始部の電磁界パルスの性質
Author(s) 牛尾, 李, 王, 河崎, 松浦, 松井
Journal 電気学会論文誌B, 116, 4, 453-459 (1996)
Abstract Pulse trains superimposed on the initial stage of Japanese winter lightning are investigated. The characteristics of these pulse trains seem to be significantly different from those of summer lightning. The shapes of pulse trains are divided into three categories: (1) consecutive small bipolar pulses similar to the summer ones. (2) a large bipolar pulse which has a static electric field change. (3) a large oscillating waveform. A correlation between the meteorological conditions and the type of these three waveforms is investigated. Each pulse included in the pulse trains is a normal bipolar waveform and its width takes the value from 5 to 52 microseconds with the mean of 18 microseconds. The time interval between successive pulses takes the value from 10 to 180 microseconds and has the mean of 52 microseconds. For each bipolar pulse, the ratio of the peak amplitude of the initial polarity to the maximum overshoot amplitude is statistically about 1.4-1.7.

Title 冬季雷放電に伴う電界変化のウェーブレット解析
Author(s) 和田, 牛尾, 川田, 河崎, 松浦, 松井
Journal 電気学会論文誌B, 116, 4, 469-474 (1996)
Abstract Electric field changes due to lightning discharges are analyzed by means of Wavelet. Since the electric field changes are the non-stationary phenomena, the conventional Fast Fourier Transform (FFT) Analysis is not sufficient to investigate the transition of electric field spectra as functions of time. The main objective of this paper is to discuss the feasibility of the forecasting of lightning to the ground to consult the transition of electric fields. For this purpose the typical electric field changes of the positive cloud to ground strokes, which were observed during winter thunderstorms, are analyzed. The transition of spectra corresponding to the preliminary breakdown pulses, return strokes and continuing currents with pulses are shown and the feasibility of forecasting is suggested.

Title シミュレーションによるレーザー誘雷の研究−不連続プラズマからの放電開始シミュレーション−
Author(s) 古河, 内田, 島田, 安田, 山中, 河崎, 山中, 石窪
Journal レーザー研究, 24, 5, 590-595, (1996)
Abstract We developed a simulation code on the discharges from discontinuous plasmas to study laser triggered lightning theoretically. And the simulations of the discharges with 2m gap from discontinuous plasmas, of which intervals are 5mm or 10mm, are performed. The model is based on plasma approximation. The effects of distortion of external electric field by tower and the progresses of the leader are included. The speed of the progresses of the leader obtained by simulations is about 3×106m/s which agrees with experimental results.