On the possibility of phosphenes being generated by the energetic radiation from lightning flashes and thunderstorms

After the first report of this phenomenon by Apollo 11 astronauts, experiments conducted in space and on the ground confirmed the creation of phosphenes by the interaction of energetic radiation with the human visual system. The aim of this Letter is to show that the energetic radiation generated in the form of X-rays, gamma rays, electrons and neutrons by thunderstorms and lightning is strong enough for the creation of phosphenes in humans. It is also pointed out that some of the visual observations reported during thunderstorms might be attributable to phosphenes excited by this energetic radiation.     

Physical processes during development of lightning flashes

The objective of this paper is to review our present understanding of the physical processes in lightning flashes during their development within or outside a cloud, following lightning initiation. This represents the ‘big picture’ of lightning development, in the scale of the cloud dimensions themselves. Since the acceptance of the bi-directional, zero-net-charge leader concept, significant changes have occurred in our understanding of the key physical processes of which a lightning flash is comprised, and in the analytical relationship between the electrical structure of a cloud and lightning parameters. These changes are discussed with an emphasis on the unifying nature of the bi-directional leader concept. To cite this article: V. Mazur, C. R. Physique 3 (2002) 1393–1409.     

Characteristics of lightning flashes striking the CN Tower below its tip

It has been observed that tall structures are sometimes struck by lightning below their tops. This phenomenon necessitates the use of special procedures for the protection of tall structures from lightning hazards. This paper focuses on the analysis of lightning flashes that struck the CN Tower below its tip over an extended period of time (1991–2005). Through the use of video images recorded during the reporting period, it was found that out of 404 flashes to the tower, only 16 hit the tower below its tip (3.96%). The distance between the tower's tip and the strike location varied from 5.4 to 70 m. Statistical analysis of flash characteristics of strikes below the tower's tip generally shows that the flash duration and the number of strokes per flash are considerably lower than those for the majority of cases, when the tower is struck at its tip. Furthermore, a trend of decrease in flash duration is found as the distance between the tower's tip and the strike location increases. Therefore, based on the analysis of the available data, lightning strikes below the top of a tall structure do not seem to pose greater danger than strikes to the structure's top, assuming that the structure is also protected along its sides. It is hoped that the presented observations and statistical analyses will be of value in the development of sophisticated measures against lightning hazards at elevated objects.     

非线性传输线高功率实验北大核心CSCD

设计了基于交叉耦合铁氧体非线性传输线高功率射频微波产生系统,系统由脉冲形成线、非线性传输线以及高功率匹配负载(或组合振子辐射天线)组成。由100kV高压电源和高压微波电缆构成单传输线高功率脉冲形成线,形成线输出脉冲幅度35kV,脉冲半宽60ns。高压脉冲经过非线性传输线的脉冲压缩和调制,与高功率匹配负载相连时,实验得到了峰峰值31kV、中心频率308 MHz、3dB带宽为13%的射频振荡脉冲;与组合振子天线相连时,实验得到了中心频率380MHz、3dB带宽为12%的宽谱辐射。实验结果与数值模拟基本吻合。     

非线性传输线高功率实验

设计了基于交叉耦合铁氧体非线性传输线高功率射频微波产生系统,系统由脉冲形成线、非线性传输线以及高功率匹配负载（或组合振子辐射天线）组成。由100 kV高压电源和高压微波电缆构成单传输线高功率脉冲形成线,形成线输出脉冲幅度35 kV,脉冲半宽60 ns。高压脉冲经过非线性传输线的脉冲压缩和调制,与高功率匹配负载相连时,实验得到了峰峰值31 kV、中心频率308 MHz、3 dB带宽为13%的射频振荡脉冲;与组合振子天线相连时,实验得到了中心频率380 MHz、3 dB带宽为12%的宽谱辐射。实验结果与数值模拟基本吻合。     

超高避雷针系统接闪效能的数值评估

针对目前超高避雷针系统日趋增多但现行标准又难以对其整体接闪效能进行有效评价的现状,基于亚网格技术发展了一种地物装置接闪效能数值评估方法,建立了超高避雷针系统接闪效能的数值评估模型,并对典型超高避雷针系统的接闪效能进行了数值评估实验,结果表明：超高避雷针系统接闪器顶端接闪概率最大,但其上部其他区域也可能遭受雷电的侧击,且接闪器上部遭受侧击的概率会随着侧击点高度的增加而增大。此外,雷击强度或雷云荷电强度对超高避雷针系统接闪器上各部分的接闪概率也有影响。雷击强度或雷云荷电强度越小,接闪器顶端的接闪概率越低,相应地接闪器上遭受侧击的概率越大,且侧击点的覆盖范围也会随之逐渐向接闪器的下部扩展。     

基于人工传输线的小型平衡型Wilkinson功分器（英）

提出了一种基于人工传输线并采用双面平行带状线实现的小型平衡型Wilkinson功分器。该器件采用人工传输线取代传统传输线以减少电路尺寸,同时引入双面平行带状线结构用来实现功分器平衡的功能。设计的功分器尺寸仅为传统Wilkinson功分器的25%。测试结果表明,设计制作的平衡Wilkinson功分器在0.83 GHz至1.05 GHz带宽范围内相位平衡度1.28,幅度平衡度0.17 dB,回波损耗大于16.79 dB,端口隔离度大于16.21 dB。测量结果和仿真结果吻合良好,证实了该功分器具有良好的性能。     

基于人工传输线的小型平衡型Wilkinson功分器（英）

提出了一种基于人工传输线并采用双面平行带状线实现的小型平衡型Wilkinson功分器。该器件采用人工传输线取代传统传输线以减少电路尺寸,同时引入双面平行带状线结构用来实现功分器平衡的功能。设计的功分器尺寸仅为传统Wilkinson功分器的25%。测试结果表明,设计制作的平衡Wilkinson功分器在0.83 GHz至1.05 GHz带宽范围内相位平衡度1.28,幅度平衡度0.17 dB,回波损耗大于16.79 dB,端口隔离度大于16.21 dB。测量结果和仿真结果吻合良好,证实了该功分器具有良好的性能。     

大规模电力系统变电线路异常实时检修方法分析

为保障大规模电力系统变电线路的正常运行,提高变电线路的工作质量,需要对大规模电力系统变电线路异常进行实时检修。当前方法利用一个函数对线路的异常进行检测,把异常码传输给调用者,直至该异常码传输至响应该异常的处理函数。该方法无法对变电线路的异常进行实时检修,降低变电线路的维修效率,还造成电网电流传输的中断,电网安全性得不到保障。为此,提出一种基于CIM的大规模电力系统变电线路异常实时检修方法。该方法利用小波变换对变电线路异常发生之后5ms内,异常点电流时域和时频域中的不同特征进行提取,并将提取结果当作变电线路异常点分类特征量。根据模糊支持向量机完成变电线路异常点的模糊分类,分析在异常点特征空间组建带状分段的隶属度函数,通过支持向量回归机构建其最佳的分类回归函数。实验结果证明,所提方法可以高效对大规模电力系统变电线路异常进行实时检修,为该领域的研究发展提供强有力的依据,具有实际利用价值。     

On the attachment of lightning flashes to grounded structures with special attention to the comparison of SLIM with CVM and EGM

Lightning attachment to vertical grounded conductors are presented with special attention to the lightning attractive radii of vertical conductors as predicted by self consistent leader inception and propagation model (SLIM), Electro Geometrical Model (EGM) and Collection Volume Method (CVM). Moreover, SLIM was utilized to model the attachment of a slanted stepped leader to a tall tower that resulted in a side flash to a point below the top of the tower. The important conclusions to be drawn from the results obtained are the following: (a) The error (caused by neglect of the connecting leader in EGM) in the predicted attractive radii and the striking distance of EGM increases with increasing structure height. However, for structures whose height is shorter than about 30 m the error associated with using EGM is less than about 20%. (b) The attractive radii predicted by the Collection Volume Method (CVM) are much larger than the ones predicted by SLIM and EGM. Thus, the use of CVM to locate the lightning conductors on a structure may undermine its safety. (c) Slanted stepped leader channels can cause side flashes in tall structures even though long connecting leaders are emitted from the top of the structure.     

利用非线性传输线产生高功率射频场

根据孤立子理论,分析了利用变容非线性传输线产生射频场的机理。利用电路仿真方法系统地研究了影响射频场产生的相关参数,发现电感和零压电容越小、输入电压越大,射频场的频率越高;电容的非线性率越大,射频场的峰值电压越高、高频成分越多。并在此基础上,仿真设计了能产生峰值功率为0.8 GW、主频为19.42 MHz射频场的非线性传输线。     

利用非线性传输线产生高功率射频场

根据孤立子理论,分析了利用变容非线性传输线产生射频场的机理。利用电路仿真方法系统地研究了影响射频场产生的相关参数,发现电感和零压电容越小、输入电压越大,射频场的频率越高;电容的非线性率越大,射频场的峰值电压越高、高频成分越多。并在此基础上,仿真设计了能产生峰值功率为0.8 GW、主频为19.42 MHz射频场的非线性传输线。     

脉冲功率传输线磁绝缘的建立与特性分析

 分析了脉冲功率传输线建立磁绝缘的暂态过程,对暂态过程中传输线的击穿与磁绝缘关系、电子的分布规律及其与建立磁绝缘的关系进行了阐述。分析了磁绝缘传输线电极间的电子分布改变传输线工作阻抗值的现象,给出了传输线稳态工作阻抗的求解方法和用稳态工作阻抗计算传输线暂态工作阻抗的方法。研究了截面尺寸变化时传输线中电子的分布和电磁波传播的折反射情况。结果表明:传输线在建立磁绝缘的过程中损失电子是必然的,损失电子是建立磁绝缘的必要条件。截面半径沿轴向变化时,其工作特性与极间距的变化有关。极间距增大时,后半段的电子电流增大,使其工作阻抗增大并与前半段相等,因而在尺寸变化处不产生反射波。极间距减小时,由于后半段提前产生损失电子,因而尺寸变化处产生反射波。     

脉冲功率传输线磁绝缘的建立与特性分析

分析了脉冲功率传输线建立磁绝缘的暂态过程,对暂态过程中传输线的击穿与磁绝缘关系、电子的分布规律及其与建立磁绝缘的关系进行了阐述。分析了磁绝缘传输线电极间的电子分布改变传输线工作阻抗值的现象,给出了传输线稳态工作阻抗的求解方法和用稳态工作阻抗计算传输线暂态工作阻抗的方法。研究了截面尺寸变化时传输线中电子的分布和电磁波传播的折反射情况。结果表明:传输线在建立磁绝缘的过程中损失电子是必然的,损失电子是建立磁绝缘的必要条件。截面半径沿轴向变化时,其工作特性与极间距的变化有关。极间距增大时,后半段的电子电流增大,使其工作阻抗增大并与前半段相等,因而在尺寸变化处不产生反射波。极间距减小时,由于后半段提前产生损失电子,因而尺寸变化处产生反射波。     

The striking distance of lightning flashes and the early streamer emission (ESE) hypothesis

The attachment of a lightning flash to a lightning conductor (or to any other structure) takes place through a connecting leader that rises from the structure towards the descending stepped leader of a lightning flash. The spatial separation between the tip of the stepped leader and the lightning conductor (or the grounded structure) at the initiation of the connecting leader is known as the striking distance. In this paper the striking distance of stepped leaders is derived as a function of conductor height, conductor radii and the prospective return stroke current. Based on these results the validity of the early streamer emission (ESE) hypothesis is discussed. According to the ESE hypothesis, the striking distance of a lightning conductor can be increased by the artificial initiation of streamers from a lightning conductor. The results cast doubt on the validity of the ESE hypothesis. This in turn calls for more experimental data and field validations before using the ESE hypothesis in standard lightning protection practice.     

Self-sustained relativistic-runaway-electron avalanches in the transverse field of lightning leader as sources of terrestrial gamma-ray flashes

The possibility of the development of self-sustained discharge in the transverse electric field of the lightning leader in the mode of generating relativistic-runaway-electron avalanches, supported by positive relativistic feedback with the participation of high-energy bremsstrahlung and positrons generated by the avalanches themselves, is analyzed. For a cylindrical geometry of the leader, the threshold of switching on the feedback was shown to be rather low. It was demonstrated that the discharge may be the source of pulses of penetrating emissions observed in the correlation with thunderstorm activity, the characteristics of which are well reproduced in the cylindrical-leader model. The penetrating emissions generated in the vicinity of the leader may be dangerous to the electronic equipment of aircrafts, as well as airplane passengers and crews.     

基于人工传输线的小型微带Wilkinson功分器

提出了一种基于人工传输线的小型微带Wilkinson功分器,该器件使用由L-C元件构成的人工传输线取代传统传输线,并使用交指电容和贴片电阻进行端口隔离。设计制作的Wilkinson功分器中心频率为915 MHz的微带3 dB功分器,等幅同相地将输入功率分配到2个输出端口,尺寸仅有传统Wilkinson功分器的25%,端口幅度平衡度±0.2 dB,相位平衡度±1°。实验结果表明：功分器带宽为0.49～1.20 GHz,插入损耗小于3.2 dB,回波损耗大于10 dB,仿真结果和测量结果吻合较好。     

基于人工传输线的小型微带Wilkinson功分器

提出了一种基于人工传输线的小型微带Wilkinson功分器,该器件使用由LC元件构成的人工传输线取代传统传输线,并使用交指电容和贴片电阻进行端口隔离。设计制作的Wilkinson功分器中心频率为915MHz的微带3dB功分器,等幅同相地将输入功率分配到2个输出端口,尺寸仅有传统Wilkinson功分器的25%,端口幅度平衡度±0.2dB,相位平衡度±1°。实验结果表明:功分器带宽为0.49～1.20GHz,插入损耗小于3.2dB,回波损耗大于10dB,仿真结果和测量结果吻合较好。     

闪电光电信号的同步观测与闪电类型模式识别

 利用宽带电场仪和光学纹波探头,对2006年夏季广东省从化地区发生的自然闪电的光电信号进行了同步观测,并对结果进行了统计分析。统计结果表明：闪电光信号脉冲的发生时间和峰值到达时间总是滞后于电信号,并且脉冲上升沿和宽度也比电信号宽;云闪的光信号在上述特征参数的滞后量、上升沿时间和脉宽时间差要比地闪回击放电大。从闪电光电信号时域信号特征的角度,利用BP人工神经网络,对闪电类型进行了模式识别研究。总体识别结果基本上能够满足要求,但是由于云闪放电过程比较复杂,获得的数据较少,所以对云闪识别的效果并不理想。     

闪电光电信号的同步观测与闪电类型模式识别

利用宽带电场仪和光学纹波探头,对2006年夏季广东省从化地区发生的自然闪电的光电信号进行了同步观测,并对结果进行了统计分析。统计结果表明：闪电光信号脉冲的发生时间和峰值到达时间总是滞后于电信号,并且脉冲上升沿和宽度也比电信号宽;云闪的光信号在上述特征参数的滞后量、上升沿时间和脉宽时间差要比地闪回击放电大。从闪电光电信号时域信号特征的角度,利用BP人工神经网络,对闪电类型进行了模式识别研究。总体识别结果基本上能够满足要求,但是由于云闪放电过程比较复杂,获得的数据较少,所以对云闪识别的效果并不理想。