Current Issue

• OBSERVATION OF POSITIVE LIGHTNING IN THE INLAND PLATEAU OF CHINA
• LIU Xin-sheng;QIE Xiu-shu;ZHANG Yi-jun;WANG Cai-wei;DONG Wan-sheng;XIAO Qing-fu;ZHANG Guang-shu;GUO Chang-ming;CHEN Ming-li;T Watanabe;M Nakano;K Nakamura;Z Kawasaki;S Sumi
• 1998 Vol. 17 (1): 1-9. 
• Abstract ( ) PDF (312KB) ( )
• In the summer of 1997, Chinese and Japanese scientists conducted jointly a comprehensive observation of positive lightning in Pingliang, Gansu province which is located in the east verge of Qinghai-Xizang Plateau. This paper presents the field experiment arrangement, measuring technique and main results obtained. During the experiment, the technique of artificial triggering lightning was used and two cases of triggered lightning were obtained. Among them the so-called 'altitude triggering technique' was used in one case, ie., the lower end of still wire pulled by ascending rocked was attached to the ground not directly but through a length of insulated nylon line. In this way the initial process of natural lightning could be reproduced more truly. A bi-directional leader process initiated from both ends of altitude wire was observed. Simultaneous measurement of current and field change as well as luminosity measurement by high speed video cammera revealed that after initiation the downward moving positive leader connected in the period of 0.7ms to the upward moving negative leader. The experiment shows that the comprehensive observation by using the technique of artificially triggered lightning and advanced instruments is conducive to revealing the characteristics of positive lightning in the inland plateau of China , and also an efficient way to study the mechanism of lightning discharge.

• THE CHARACTERISTICS OF THE CHANNEL LUMINOSITY OF TRIGGERED LIGHTNING FLASHES
• WANG Cai-wei;LIU Xin-sheng;DONG Wan-sheng;ZHANG Cui-hua
• 1998 Vol. 17 (1): 10-23. 
• Abstract ( ) PDF (484KB) ( )
• The luminous characteristics of the channel of artificially triggered lightning flashes were studied by use of digital photographic data obtained with a high-speed CCD camera system(frame rate 1 000F/s) at very close range to the lightning. The techniques for triggering lightning were conventional one with a rocket trailing a grounded wire as well as a newly-developed one called altitude-triggering with the lower end of the wire not connected to the ground. The results showed that the transversal distribution of channel luminosity was essentially symmetric. The duration of the channel luminosity and the number of light pulses for individual flash could be different noticeably, however, they had four common luminous phases, which associated with specific discharge processes. The light pulses during a flash were found to well correspond with that of electric field change and lightning current. The initial light pulse was produced by the upward leader propagating into clouds and the vaporization of the wire as a result of leader development; channel had being appreciably luminant when M component occurred; whereas the channel luminosity had become very weak or even ceased when light pulse of return stroke appeared. The lowest part of the lightning channel of an altitude triggered flash consisted of metal-vaporized and air-ionized ones, whose luminous behaviors were quite different:the channel luminosity of the latter was more intensive and lasted for a longer time, especially during the steady luminous period.

• THE DOWNWARD-MOVING LEADER OF THE LIGHTNING FLASH TRIGGERED AT ALTITUDE AND ITS BEHAVIOR IN CONNECTING TO THE GROUND
• WANG Cai-wei;ZHANG Yi-jun;XIAO Qin-fu;LIU Xin-sheng
• 1998 Vol. 17 (1): 24-33. 
• Abstract ( ) PDF (354KB) ( )
• In the field experiment of artificially triggering lightning conducted near Nanchang, Jiangxi in the summer of 1996, 3 lightning flashes were successfully triggered by use of newly-developed technique with ungrounded rocket-wire system in negative ambient electric field of thunderclouds. A high-speed digital camera with 1 000F/s framing rate was used for the observation. Data analysis revealed the characteristics of the initiation, propagation and connection to the ground of the downward-moving negative leader, which progressed at a lower speed and showed zigzag, branching on its way to the ground, and finally terminated on the tip of a 4m high, well grounded lightning rod. The current density along the channel was not uniform on the moment when the downward leader touched the ground. A physical model of leader inception and propagation in altitude triggered lightning was presented through case analyses.

• INITIAL PROCESS DURING ONE NEGATIVE GROUND LIGHTNING DISCHARGE IN ZHONGCHUAN AREA
• QIE Xiu-shu;YU Ye;ZHANG Guang-shu;LIU Xin-sheng;GUO Chang-ming;T Watanabe;Z Kawasaki;M Nakano;K Nakamura;Wang Dao-hong;T Ushio
• 1998 Vol. 17 (1): 34-43. 
• Abstract ( ) PDF (342KB) ( )
• The initial processes in one multiple-stroke flash to ground have been discussed by using 4-site measurements of the electrostatic field changes synchronized by GPS on the ground in Zhongchuan area near Lanzhou. It has been found that ground flashes usually follow cloud discharges which lasted 170ms~300ms and consisted of several K-changes. The sources of a series of pulses included in 3 K-changes are located by using time difference of arriving different site. It is concluded that K-changes initiated from negative charge region in the middle part of the cloud in a manner of negative streamer, and propagated downward to the positive charge region at the bottom of the cloud with an average speed of 1.5×10 ⁷m/s. Positive and negative charge center are located in 2.5~3.5km and 5.0~6.0km above the ground respectively. The cloud discharge before ground discharge is important for the initiation of ground discharge because of the well ionized discharge channel in the cloud. The speed of stepped leader below thunderstorm to the ground is about 2.7×10 ⁵m/s. Dart leader propagates following the return stroke channel with a speed of 2×10 ⁷m/s at the beginning, and becomes slower near the ground with a speed close to that of stepped leader.

• RADIATION ELECTRIC FIELD OF RETURN STROKE AND ATTACHMENT PROCESS NEAR THE GROUND
• QIE Xiu-shu;GUO Chang-ming;ZHANG Cui-hua;LIU Xin-sheng;T Watanabe;WANG Dao-hong;Z Kawasaki;M Nakano;K Nakamura;T Ushio
• 1998 Vol. 17 (1): 44-54. 
• Abstract ( ) PDF (466KB) ( )
• The characteristics of return stroke and the slow front process in the radiation field of return stroke have been analyzed using the data obtained by slow antenna with 1 μs time resolution in Zhongchuan area near Lanzhou. It has been found that the duration of slow front for 18 positive and 85 negative first return stroke are 19.2 μs, with a standard deviation of 6.1 μs and 9.4 μs, with a standard deviation of 3.9 μs,and while that of negative subsequent return stroke is 4.3 μs, with a standard deviation of 3.1 μs. The amplitude percentage to the peak is 30%~70% for positive first return stroke, 20%~60% for negative first return stroke, and 10%~30% for negative subsequent return stroke. The peak discharge current and striking distance are 56.08kA and 137.2m for one positive, 16.92kA and 62.8m for three negative first return strokes respectively. The preliminary analysis shows that the slow front is a complicated process, and it appears that the slow front begins at the initiating instant of the attachment process, and moves downward from the connecting point to the strike point on the ground, and moves upward along the stepped leader, untill the downward leader arrives at the ground.

• EXPERIMENT OF ARTIFICIALLY TRIGGERED LIGHTNING IN ALTITUDE AND ANALYSIS OF ITS CHARACTERISTICS
• ZHANG Yi-jun;LIU Xin-sheng;WANG Cai-wei;XIAO Qing-fu;DONG Wan-sheng;WANG Huai-bin
• 1998 Vol. 17 (1): 55-64. 
• Abstract ( ) PDF (348KB) ( )
• In this paper,the characteristics of artificially triggered lightning flashes in altitude in Nanchang,1996 was analyzed and electric parameters in the stage of rocket lifting were evaluated. The results indicated that triggering height of artificially triggered lightning in altitude was 2 time higher than that of artificially triggered lightning flashes on the ground. In the stage of rocket lifting,a positive electric field on the ground was caused by artificially triggered lightning in altitude and a negative electric field on the ground was caused by artificially triggered lightning on the ground. For negative electric field on the ground,two artificially triggered lightning flashes on the ground produced positive charges on the path of rocket. Their average magnitude were 1.0×10 ^-5C/m and 6.7×10 ^-6C/m respectively and average corona currents were 0.68mA and 0.57mA respectively. However two artificially triggered lightning flashes in altitude produced positive charges on the top of path of rocket and negative charges on the bottom of path of rocket,the maximum values of charge were 3.7×10 ^-5C/m and 4.5×10 ^-5C/m respectively. The positive and negative leader of artificially triggered lightning in altitude propagated up and down respectively. When negative leader connected with the ground,a higher current impulse was caused. It is similar to return stroke. The propagation of leader was stepped and the characteristics of return stroke were similar to that of natural lightning discharge. There were continuing current superimposed M changes after return stroke. There was positive correlation between lightning current and relative light intensity.

• THE INITIATION AND PROPAGATION OF LIGHTNING LEADER IN POSITIVE AMBIENT ELECTRIC FIELD
• WANG Cai-wei;LIU Xin-sheng;DONG Wan-sheng;ZHANG Cui-hua;XIAO Qing-fu
• 1998 Vol. 17 (1): 65-74. 
• Abstract ( ) PDF (376KB) ( )
• In order to investigate the detailed characteristics of positive lightning discharges in inland plateau of China, scientists from China and Japan conducted a joint field experiment on triggered lightning in Pingliang, Gansu province of China in July to August of 1997. In this paper, the characteristics of the initiation and propagation of initial leaders of two lightning flashes triggered in positive ambient electric field have been studied by analyzing photographic data obtained with a high speed digital camera system installed 3.5km away from the triggering site and the discharge current measured at the bottom of lightning channel. Results showed that the analyzed triggered lightnings were initiated by upward-going negative leader emerged from the tip of ascending rocket, and both of which were short duration discharges without return stroke. The leader tended to speed up during its vertical propagation with a mean speed of the order of 3.5×10 ⁵m/s, the durations of two discharges were 17ms and 26ms separately. A number of branches might occour during leader propagation in positive ambient field, however, only one or two branches could enter clouds, while most of them existed only for a few ms and then died out. The luminosity of the main channel combined the changes of that of individual branch, and it in turn showed a good correspondence with lightning currents measured at the bottom of the channel.

• THE NUMERICAL EXPERIMENTS OF RAINDROP GROWTH IN INTRA-CLOUD LIGHTNING DISCHARGE PROCESSES
• ZHANG Min-feng;GE Zheng-mo;LIU Xin-sheng
• 1998 Vol. 17 (1): 75-83. 
• Abstract ( ) PDF (371KB) ( )
• The numerical experiments of raindrop growth under the condition of intra-cloud lightning discharge and the raindrop growth evolution series and motion trails on different electric, charge count and electrical angle are studied in this paper. The results show that the implication on raindrop growth under two dimension model is different from under one dimension .The growth with different parameters are very fast when electric field and charge count change. If two parameters change in same step, the larger multiplication values are, the larger raindrop growth amplitude are. The responses of raindrop on the absolute change of electric field angle are week. The raindrop trails under different conditions are quasi-periodic.

• INFLUENCE OF CORONA IONS NEAR THE GROUND ON THE INITIATION OF ALTITUDE TRIGGERING LIGHTNING
• QIE Xiu-shu;LIU Xin-sheng;YU Ye;ZHANG Guang-shu;ZHANG Yi-jun;XIAO Qing-fu
• 1998 Vol. 17 (1): 84-94. 
• Abstract ( ) PDF (446KB) ( )
• The electric field and charge density under one thunderstorm have been studied by using a one-dimension model. Corona ions produced from ground irregularities will reach up to 500m in 1min if they are not captured by aerosols. Space charge layer is as thick as several hundreds meters with the evolution of thunderstorm. The analyses of electric field in altitude show that there is an important factor which affect triggering lightning success besides of the length of wires spooling by the rocket. That is the rocket should reach up to higher ambient electric field for the propagation of streamer from the tip of the rocket. Meanwhile, the higher ambient electric field in lower space is conducive to the propagation of streamer at the bottom of rocket-wire system and the breakdown of the isolated gap between the bottom of wire connecting to the wire and the grounded wire. One example of electric field for successful altitude triggered lightning is about 50.0kV/m, and the discharge begins with the positive streamer initiation at the bottom of the rocket-wire system. For the artificially triggering lightning experiment, it is suggested that the rocket lunching instant could be determined by referring the electric field at 500m above the ground, which is greater than 50kV/m in northern China and 25kV/m in southern China.

• STUDIES ON ARTIFICIALLY TRIGGERED LIGHTNING AND PLANT GENE MUTATION
• HE Li-xia;DONG Wan-sheng;FENG Da;LI Rui
• 1998 Vol. 17 (1): 95-100. 
• Abstract ( ) PDF (211KB) ( )
• In this paper, based on studies of the morphology and the cytology of plants( Limonium aureum and Limonium bicolor) that were mutagenized by the artificially triggered lightning, the mechanism of the artificially triggered lightning causing plant mutation was further explored. The results indicated that the experiment of artificially triggered lightning would play specified role in plant mutation breeding as a physics factor or inductive stimulus.

• A MULTI-CHANNEL HIGH SAMPLING AND LONG RECORDS SYSTEM OF DATA ACQUIRING AND ANALYZING
• DONG Wan-sheng;LIU Xin-sheng;ZHANG Guang-shu
• 1998 Vol. 17 (1): 101-105. 
• Abstract ( ) PDF (191KB) ( )
• In this paper, the hardware constitute and the design of controlling and analyzing program of a multi-channel high sampling and long record system data acquiring and analyzing are described. The synchronous data of current, electric field change, d E/d t and magnetic field et al with the order of microsecond are firstly acquired by using this system during artificially triggered lightning experiment carried in Pingliang country, Gansu on July 1997. Using this system, the measured lightning waveform can be analyzed and carried out multi signal deal.

• STILL PHOTOGRAPH AND ITS CHARACTERISTIC ANALYSIS OF ARTIFICIALLY TRIGGERED LIGHTNING
• LIU Xin-sheng;XIAO Qing-fu
• 1998 Vol. 17 (1): 106-110. 
• Abstract ( ) PDF (173KB) ( )
• Still photographes taken at close range of artificially triggered lightning are exhibited and analysed in this paper. Some macroscopic characteristics of lightning discharge can be deduced from the photographes.