The Principles of Developing the Ball Lightning Theory

Criteria for developing the ball lightning theory based on the results of observations are analyzed. It is assumed that the key features of ball lightning are a large energy (more than 10⁶ J) and long lifetime (more than 1 s). We exclude from consideration theories which do not explain these features and concentrate our attention on the analysis of three models where the large energy of the autonomous ball lightning and the forces providing the compression of the ball lightning substance are taken into account. The first considered model was developed by Geert Dijkhuis, in which the appearance of a force directed towards the system center is attributed to the Bose condensation of vortices of degenerated electrons as well as to gradient forces arising due to a nonuniform distribution of the electron density over the ball lightning volume. The second model proposed by Vladimir Bychkov assumed that the energy reservoir of ball lightning is polymer threads carrying a big electric charge. Our model assumes that the energy is stored in the form of kinetic energy of ions which the positively charged core of ball lightning is thought to consist of. The core is compressed by a dielectric shell which, in turn, is shrunk by the force created due to the nonuniform electric field of the core. The merits and limitations of these and other models are discussed.     

Electric fields from model lightning discharges in a neutral atmosphere

The electric fields created by lightning discharges in a neutral atmosphere are calculated in the time representation. It is shown that asymmetric strokes containing horizontal currents can generate pronounced pulsed electric fields. A high-power quasistatic field can influence the middle atmosphere together with pulses. The motion of the current wave in a complex-geometry stroke channel can lead to an increase in the number of emitted pulses. At the periphery of the lightning cell, upon the arrival of the pulse, the electric field vector turns upward, to the stroke axis, and sideward. We also expect an increase in atmospheric turbulence due to convection at the frontal part of the cloud. The emerging inhomogeneities of the atmospheric temperature and density can facilitate the onset of plasma processes generated by the electric field of a strong thunderstorm. Since convection and the focusing electric fields are concentrated at the periphery, their joint action can lead to the appearance of circular and prolate luminous formations. Institute of Radiophysics and Electronics of the National Academy of Sciences, Khar’kov, Ukraine; The University of Electro-Communications, Tokyo, Japan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 6, pp. 699–722, June, 1998.     

Electric charge of a lightning ball

The electric charge of a lightning ball is found by comparing the electrohydrodynamic stabilities of a charged drop in an electrostatic suspension and a lightning ball floating in a superposition of the gravitational field and the surface electric field. It has been assumed that the electric field strength at the surface is limited by a breakdown value. For a lightning ball radius of 15 cm, its charge is estimated as several microcoulombs. Accordingly, the density of electrostatic energy accumulated in the lightning ball is on the order of one-hundredth of a joule per square centimeter. The density of the material that constitutes the lightning ball has been estimated for the case when the electric field strength at the site of its origination is several times higher than that in fine weather. The density of the lightning ball turns out to differ from that of air by only a few percents.     

雷暴云内电场力对起电和电荷结构的反馈作用

利用美国国家强风暴实验室(NSSL)发展的耦合了详细起电机制和放电过程的中尺度电耦合数值模式WRF(weather research forecasting)-Elec,在NSSL云微物理双参数化方案中增加了电场力对霰、雹粒子降落末速度的影响,完善了WRF-Elec模式的物理过程,建立了双向耦合WRF-Elec模式.利用改进后的WRF-Elec模式,通过敏感性数值实验,定量分析了雷暴云内电场力对起电和电荷结构的反馈作用.结果发现:雷暴云发展旺盛阶段,由于电场力作用,霰、雹粒子质量加权平均降落末速度的瞬时变化极值可以超过4 m/s,但这种情况仅出现在雷暴云内局部区域,并且维持时间较短;电场力对直径小且数浓度较低的霰和雹粒子影响较大,但这种影响不是由单一物理量决定,而是由电场强度和霰、雹粒子的电荷密度、极性以及粒子的直径与数浓度共同决定;电场力通过对霰、雹粒子降落末速度的调整,增强了雷暴云内感应、非感应起电率,且前者远大于后者,云内局部产生-0.6—1.2 n C/m~3总电荷密度的变化,从而使电荷结构重新分布,局部垂直电场强度增强5 k V/m,总闪电数增加,与此同时,雷暴云内降水粒子的微观增长过程也发生改变.总体上,电场力对雷暴云起电过程的作用为正反馈,电场力对雷暴云电荷结构的反馈作用不可忽略.     

First experimental observations of neutron bursts under thunderstorm clouds near sea level

The connection of short-term neutron bursts near sea level with the electric and geomagnetic atmospheric fields during thunderstorms in 2009–2011 has been experimentally studied. The data from the cosmic-ray spectrograph named after Kuzmin, an electrostatic fluxmeter, and a three-component fluxgate magnetometer in Yakutsk have been analyzed. It has been shown that short-term (no longer than 4 min) neutron bursts are due to negative lightning discharges. The bursts are detected at the ground level 1–3 km below thunderstorm clouds. In this case, the neutron flux is about 4 × 10⁻³ cm⁻² s⁻¹. The minimum energy of the neutrons that are efficiently detected by the monitor is about 10 MeV. It has been found that short-term neutron bursts are detected when the electric field strength reaches a threshold value of −16 kV/m.     

Water vapor condensation and the collapse of superheated water drops as possible causes of ball lightning

Ball lightning is modeled by the bulk of humid air heated to temperatures of 600–650 K and containing a multitude of charged drops and microbubbles of size 10⁻⁵ cm or less, as well as water vapor heated to a near-critical temperature. The condensation of the vapor in the microbubbles, followed by the cooling of resulting droplets, generates energy spent on the thermal radiation of ball lightning. The radiation of light and radio waves is explained by the motion of ions and electrons in the electric field of charged bubbles and droplets and by the thermal rotational motion of charged droplets. As a result of coagulation, the droplets overheat and tend to collapse. An external electric field, supersaturated water vapor condensation, and a number of other factors may contribute to the ball lightning explosion energy.     

New Physical Mechanism for Lightning

The article is devoted to electromagnetic phenomena in the atmosphere. The set of experimental data on the thunderstorm activity is analyzed. It helps to identify a possible physical mechanism of lightning flashes. This mechanism can involve the formation of metallic bonds in thunderclouds. The analysis of the problem is performed at a microphysical level within the framework of quantum mechanics. The mechanism of appearance of metallic conductivity includes the resonant tunneling of electrons along resonance-percolation trajectories. Such bonds allow the charges from the vast cloud charged subsystems concentrate quickly in lightning channel. The formation of metal bonds in the thunderstorm cloudiness is described as the second-order phase transition. A successive mechanism for the process of formation and development of the lightning channel is suggested. This mechanism is associated with the change in the orientation of crystals in growing electric field. Possible consequences of the quantum-mechanical mechanism under discussion are compared with the results of observations.     

Current Problems of Electrodynamics of a Thunderstorm Cloud

Electrodynamics of a thunderstorm cloud is considered with allowance for recirculation and multiflow motion of charged intracloud particles. In this simulation, the large-scale electric-field emerges due to the charge separation at the process of air convection and develops through the oscillation regime in the initial and final stages of the thunderstorm evolution. These oscillations qualitatively explain the observed behavior of the electric field of a thunderstorm. On the other hand, the multiflow convection is unstable and leads to generation of small-scale electrostatic waves (wavelength from 1 to 100 m) with amplitude reaching the conventional breakdown value. Such an instability can initiate microdischarge intracloud activity at the preliminary stage of the lightning discharge and between individual return strokes. We propose a three-dimensional cellular automata model which describes the main features of the preliminary stage of the lightning. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 9, pp. 810–822, September 2005.     

基于小波的雷暴强放电前地面电场的多重分形分析

根据远离平衡的复杂系统演化的雪崩性和自相似倍增串级性，强调了多重分形工具的重要；利用青藏高原中部地区雷暴放电的地面电场仪资料，基于多重分形谱的小波估计方法，对强放电前雷电活动的多重分形特征进行了分析，发现多重分形谱可用推广的多重分形二项倍增串级模式描述，强放电前放电过程具有强烈的奇异性和明显的多重分形性，谱宽度Δα＞1.6，最小标度指数α_min＜-0.3；随着放电的活跃，Δα表现出明显的增加，而强的放电则发生在随后Δα的高值区或下降区，并对相关的原因进行了讨论. 关键词： 多重分形 雪崩 倍增串级 小波 闪电放电     

基于RAMS V6.0的非感应起电机制评估和雷暴初期电荷结构模拟

数值模式是研究雷暴内起电和电荷结构的重要工具. 本文将Takahashi (1978) 和Saunders (1991) 两种主流非感应起电机制加入最新版本的中尺度模式RAMS(Version 6.0), 建立了一个区域大气-电耦合中尺度雷暴云模式, 据此对发生于北京的一次雷暴过程首次放电前的电荷结构和水成物粒子起电情况进行了较成功的模拟. 结果表明, Takahashi (1978) 和Saunders (1991)方案模拟的雷暴电荷结构在电场达到击穿阈值时均呈现三极性特征, 但Takahashi和Saunders方案模拟的雷暴电荷结构演变过程有一定的差异, Takahashi方案的电荷结构从起电到放电都是三极性特征, Saunders方案的电荷结构从反偶极性演变为三极性. 此外, 两种方案的模拟结果均表明雨滴是雷暴云低层的正电荷载体, 聚合物和霰是高层的主要电荷载体, 霰的电荷中心分布形态与雷暴云的总电荷分布形态相似.     

雷暴电场对宇宙射线次级粒子μ 子的影响研究

西藏羊八井宇宙射线观测站的中子监测器主要探测宇宙射线次级粒子中能量在500 MeV—20 GeV的核子成分和少量的负μ子成分. 本文分析了2008—2010年观测站附近发生的62次雷暴期间中子监测器和大气平均电场仪的同步观测资料, 发现27次雷暴期间中子监测器计数率发生明显变化, 显著性S>5σ, 其中13次变化显著, 显著性S>10σ . 显著性S>10σ的13次个例信号变化百分比与地面电场场强幅值之间存在大体一致的变化趋势, 而显著性在5σ <S<10σ之间的14次个例信号变化百分比与地面电场场强幅值之间不存在相似的变化趋势. 较强雷暴当顶时中子监测器计数率变化一般不明显, 而中子监测器计数率变化明显的个例则多发生于雷暴云不当顶, 但探测器仍处于雷暴云下部正电荷层的控制范围之内时, 或者当顶雷暴处于形成或消散阶段. Dorman等把雷暴期间中子监测器计数率的变化归因于雷暴云内电场对宇宙射线次级粒子μ子的作用, 并建立了雷暴期间中子监测器计数率变化与雷暴地面电场相关联的理论. 本文分析发现雷暴期间羊八井中子监测器计数率变化与地面电场场强之间相关性较小或者没有相关性, 不支持Dorman的理论.     

Absorption of gamma-ray photons in a vacuum neutron star magnetosphere: II. The formation of “lightnings”

The absorption of a high-energy photon from the external cosmic gamma-ray background in the inner neutron star magnetosphere triggers the generation of a secondary electron-positron plasma and gives rise to a lightning—a lengthening and simultaneously expanding plasma tube. It propagates along magnetic fields lines with a velocity close to the speed of light. The high electron-positron plasma generation rate leads to dynamical screening of the longitudinal electric field that is provided not by charge separation but by electric current growth in the lightning. The lightning radius is comparable to the polar cap radius of a radio pulsar. The number of electron-positron pairs produced in the lightning in its lifetime reaches 10²⁸. The density of the forming plasma is comparable to or even higher than that in the polar cap regions of ordinary pulsars. This suggests that the radio emission from individual lightnings can be observed. Since the formation time of the radio emission is limited by the lightning lifetime, the possible single short radio bursts may be associated with rotating radio transients (RRATs).     

Shielding failure rate calculation by means of downward and upward lightning leader movement models: Effect of environmental conditions

In this paper the effects of environmental conditions on shielding failure rate (SFR) of transmission lines are investigated. The study utilizes a previously published work in which leader progression model for lightning upward and downward leaders are used to calculate the SFR. Taking into account the effects of reduced air density and humidity on the parameters of upward leader model and wind pressure on the movement of lightning leaders and wires, SFR and maximum lightning stroke current causing shielding failure are computed. The electric field in all simulations is calculated by means of charge simulation method. The results of simulation show that the effects of relative air density and height of installation are quite higher than that of the wind pressure and humidity while the humidity has the lowest impact on the SFR of investigated transmission line.     

Experimental research on ball lightning

Summary Experiments on producing ball lightning were made with discharge in flammable gas and/or aerosol. A long lifetime (2 s) ball lightning was observed in 2.7% ethane and 100 cm³ cotton fibers, and in 1.5% methane and 1.9% ethane.     

西藏地区近地晴天大气电场气象效应和时间变化研究

基于西藏羊八井宇宙线观测站在2006年3月至2011年6月期间记录的近地大气电场数据, 分析研究了该地区近地晴天大气电场气象效应和时间变化特征. 气象效应分析结果显示, 该地区近地晴天大气电场与三个气象参量(大气压强、温度和相对湿度)的长时间变化趋势基本一致, 并有明显的季节效应. 冬春季, 大气电场强度整体水平相对较低, 约为0.14 kV/m; 夏秋季, 电场强度水平相对较高, 为0.18 kV/m左右. 近地晴天大气电场强度与大气温度间的线性相关性最强, 拟合相关系数达到0.89; 与大气压强和相对湿度间的线性相关性相对较弱, 拟合相关系数依次为0.43和0.53. 傅里叶分析结果表明: 晴天大气电场时间变化受太阳日周期、半太阳日周期及其三、四次谐波分量调制作用, 调制强度依次减弱. 西藏地区近地晴天大气电场日变化特征呈大陆简单型, 即双峰双谷. 主、次峰谷分别出现在白天和夜间, 主峰谷出现的早晚因季节不同略有差异, 次峰谷出现的早晚因季节不同差异相对较大.     

Production of ball-lightning-like luminous balls by electrical discharges in silicon

We performed electric arc discharges in pure Si to generate luminous balls with lifetime in the order of seconds and several properties usually reported for natural ball lightning. This simple experiment does not rely on energy sources and excitation mechanisms that are improbable in the natural phenomenon and clearly demonstrates the role of vaporization and oxidation of Si, as proposed by the Abrahamson-Dinniss theory for ball-lightning formation.     

A preliminary study on time series forecast of fair-weather atmospheric electric field with WT-LSSVM method

Accurate forecasting of fair-weather atmospheric electric field is of great importance to denote the climate change, and it also plays a vital role in lightning forecasting. In this paper, the WT (Wavelet transform)-LSSVM (Least squares support vector machine) method is proposed to develop a model to forecast time series of fair-weather atmospheric electric field. The application experiments with data from Verhnee Dubrovo, Dusheti, and Voeikovo stations show that the predicted data and observed value have the same tendency. The correlation coefficients between them are 0.8149, 0.6395 and 0.7308, while the MSE are 16.9869 V/m, 28.8876 V/m and 32.2163 V/m, respectively. Furthermore, comparing to LSSVM and ANN, WT-LSSVM is a superior method to predict the monthly mean values of fair-weather atmospheric electric field.     

Similarities of dielectric surface flashover under atmospheric conditions for pulsed unipolar and RF excitation

Mechanisms in vacuum surface flashover caused by rf (f < 10 GHz) or unipolar voltages are virtually identical. Similarities between rf (representing high-power microwave window breakdown on the high-pressure side) and unipolar surface flashover are expected in an atmospheric environment as well. Two separate experimental setups were utilized to investigate both unipolar flashover and rf window flashover under atmospheric conditions while controlling excitation, temperature, pressure, humidity, and type of gas present, all under a similar electric field-surface geometry. The local electric field at the flashover initiating points has been numerically calculated in detail for all test geometries. For both rf and unipolar pulsed excitation, the flashover dynamics are changed by the application of UV light to the dielectric surface. A UV prepulse has a distinct impact on the arc’s path and a tendency to decrease the hold-off electric field. The effect of humidity on the hold-off electric field for both pulsed unipolar and rf excitations, along with temporally resolved emission spectroscopy of the flashover event, is discussed. This work was funded by the Cathode and HPM Breakdown MURI program and managed by the Air Force Office of Scientific Research (AFOSR) and by Sandia National Laboratories.     

A lightning initiation mechanism: application to a thunderstorm electrification model

The use of numerical models has greatly increased our understanding of the electrical and microphysical process within electrified clouds. We use the University of Washington, 1.5-dimensional thunderstorm model to examine the effects of including a runaway electron based lightning initiation mechanism. We find that this mechanism can significantly alter the electrification history of modeled storms and produce vertical electric field profiles that are very similar to those of observed storms. To cite this article: R. Solomon et al., C. R. Physique 3 (2002) 1325–1333.     

On the lightning hazard warning using electrostatic field: Analysis of summer thunderstorms in Spain

This work presents an analysis of lightning warnings based on atmospheric electrostatic field measurements achieved in the city of Terrassa (northeastern Spain). Seven summer thunderstorms were analyzed. Lightning location data were obtained from two lightning detection networks that provide cloud-to-ground (CG) and intra-cloud (IC) flash information. Warning behaviour was studied on the basis of the “two area method” using both electrostatic field (EF) thresholds and polarity reversal detection. The study of the total lightning locations (CG + IC) with respect to the electric field mill (EFM) site lets investigate the possible EF threshold and EF polarity inversion values useful for warning. The probability of detection (POD) and the false alarm ratio (FAR) were evaluated in both cases obtaining slightly better results by using polarity change criteria. The paper also includes a discussion about the lead times (LTs) obtained between the trigger of a warning and a CG located in the area of concern (AOC).