Influence of thunderstorm atmospheric conditions on the properties of ball lightning

Rank-correlation methods are used to investigate the influence of thunderstorm atmospheric conditions on the lifetime (observation time) and diameter of ball lightning on the basis of an analysis of observations from the Stakhanov-Cole-Bychkov ball lightning PC database. For the analysis ball lightning events are ranked by diameter, the weather conditions are ranked in relation to humidity, which correlates with the charge state of the atmosphere, and thunderstorm conditions are ranked in relation to the electric field of the atmospheric ground layer. A statistical analysis shows that the lifetime and diameter of ball lightning decrease under conditions of increasing humidity and increasing electric field. The plausibility of this result from the standpoint of various existing ball lightning models is discussed. Zh. Tekh. Fiz. 67, 117–122 (April 1997)     

Mechanisms of coupling of aeroelectric and temperature fields in the lower atmosphere

Based on synchronous observations of the aeroelectric field and the air temperature, performed in August–October 2002 and June–September 2003 at the measuring facility of the mid-latitude geophysical observatory “Borok” (Yaroslavsl’ Region, Russia), we conclude that correlative relations exist between the aeroelectric-field intensity E and the air temperature T in the atmospheric surface layer. We reveal positive correlation between the temperature and electric-field variations under conditions of unstable stratification (late morning-day) and negative correlation under stable stratification (late evening-night). A simultaneous increase in the amplitude of pulsations of the electric field and the temperature occurs most frequently near the local midday. Intense variations in the electric field correspond to variations in the temperature field with a close time period. A positive temporal shift of variations in E with respect to variations in T, which reaches 40 min, is observed during enhanced temperature activity. The structure-temporal analysis of experimental data from remote sensing of the temperature and electric-field variations at five points is performed. We find simultaneous aeroelectric and temperature coherent structures accompanied by short-period pulsations of the field intensity and the air temperature in the atmospheric surface layer. We discuss possible mechanisms of coupling of the aeroelectric-field intensity and the atmospheric air temperature to describe their positive correlation under conditions of unstable stratification (late morning-day) and negative correlation in the late evening and at night. Enhancement of electric activity, which is stipulated by the intensification of turbulent convection and the formation of aeroelectric structures, seems the most significant process. With allowance for nonlocality of the electric field, this process can in particular explain a substantial lead of the aeroelectric-field perturbations compared with the correlated positive temperature perturbations. In this case, the formation of warm “quasi-front,” which is accompanied by the lifting of the near-surface air abundant in moisture and charged particles to the higher atmospheric layers, can play an important role. Other mechanisms of the field-temperature coupling take into account a decrease in the conductivity of near-surface air due to the condensation of water vapor during its cooling, as well as an increase in the mobility of light ions with increasing air temperature. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 1, pp. 35–52, January 2006.     

Electroluminescence study of polarization changes in lead magnoniobate crystals in pulsed electric fields

Electroluminescence is used to study changes in the polarization of crystals of a model ferroelectric relaxor, lead magnoniobate (PMN), in pulsed electric fields. The amplitude of the electoluminescence pulses produced during polarization and depolarization of PMN crystals is found to depend on the duration of the applied electric field pulses if this duration is shorter than the most probable time for polarization buildup. These data provide evidence of rapid changes in the polarization through realignment of the domain and heterophase structure at temperatures above the temperature for destruction of the induced macrodomain ferroelectric phase and evidence of an “excited” polarization state for short-lived pulses whose decay is accompanied by an enhancement in the amplitude of the depolarizing luminescence pulse and by a reduction in the time delay of its emission following the end of the field pulse. Fiz. Tverd. Tela (St. Petersburg) 39, 341–343 (February 1997)     

Electric field perturbation caused by an increase in conductivity related to seismicity-induced atmospheric radioactivity growth

The influence of conductivity perturbation in the lower atmosphere on the DC electric field over a seismic region is investigated. This perturbation is related to the emanation of radon and other radioactive elements into the lower atmosphere as the seismic activity increases. An increase in the level of atmospheric radioactivity results in the appearance of additional ionization sources. The altitude dependence of the ion formation rate is calculated. An ionization source changes the atmospheric conductivity because of the appearance of ions with an equilibrium number density. The perturbation of the atmospheric conductivity is calculated as a function of the altitude. Lower atmosphere conductivity changes disturb the electric current that flows in the global atmosphere-ionosphere circuit. This disturbance is caused by an external current over a seismic region. DC electric field perturbations on the Earth’s surface and in the ionosphere are estimated. Published in Russian in Khimicheskaya Fizika, 2007, Vol. 26, No. 4, pp. 39–44. The text was translated by the authors.     

依据光谱研究闪电回击通道核心的特征参数

闪电回击通道核心中的大电流及其强电磁辐射是引发多种雷电灾害的主要根源。随着现代科技的飞速发展,闪电防护工作显得越为重要。为了完善闪电防护系统,需要从描述闪电回击通道核心的特征参数入手深入研究闪电通道形成和发展过程的微观物理机制。截至目前,光谱观测是获取闪电通道核心特征参数的最佳手段。2015年夏天在青海高原地区的野外试验中,利用由高速摄像机作为记录系统组装的无狭缝光栅摄谱仪,结合快天线地面电场测量仪,记录到一次包括四个回击的云地闪电放电过程的光谱以及与之同步的快电场变化信息。依据光谱,结合等离子体理论计算得到闪电回击通道核心的电导率。在此基础上,应用闪电电动力学模型计算了闪电回击速度、峰值电流、贯穿通道核心的电磁场以及通道核心单位长度的峰值功率等特征参数。结果表明,回击速度在(1.2～2.3)×108 m·s-1的范围内;贯穿回击通道核心的轴向电场、径向电场和磁感应强度的最大值分别在(1.42～1.74)×105 V·m-1,(8.22～9.99)×108 V·m-1和(1.51～2.83) T的范围内。当闪电回击的峰值电流在(7.52～24.05) kA的范围内时,回击通道核心的峰值功率在(0.63～1.92)×109 W·m-1的范围内。另外,分析了电导率、起始电场峰值、回击速度和峰值电流与峰值功率之间的相关性,结果发现峰值电流和峰值功率具有良好的线性关系。研究结果可为探索闪电回击通道形成和发展过程的微观物理机制提供参考依据。     

Modeling of the Electric-Field Dynamics in the Atmosphere Using the Test-Structure Method

We propose the test-structure method for modeling of electric-field pulsations in the atmosphere. Numerical calculations necessary for interpretation of the behavior of experimental spectra and structure functions of the electric field are performed. Analysis of experimental data shows that the aeroelectric-field strength, being a nonlocal quantity, is formed by an inhomogeneous distribution of space charges surrounding the observation point. Quantitative assessments of the state of the atmospheric boundary layer, electro-gas-dynamic turbulence and convection parameters are discussed on the basis of spectral and structure functions of the electric field. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 48, No. 8, pp. 648–660, August 2005.     

On the relationship between the lightning electromagnetic field and the channel-base current based on the TL model

A set of approximation expressions relating the lightning channel-base current and the lightning electric and magnetic fields on earth surface are proposed respectively in the near-zone and far-zone, by employing the transmission line (TL) model. The derived expressions show that, the electric and magnetic fields waveforms can be expressed approximately by the channel-base current waveform with different factors at a certain distances, whether in the near-zone or far-zone. The factors can be expressed in terms of the return stroke wavefront speed v, the speed of light c, and the horizontal distance r between the return-stroke channel and the observation point.     

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.     

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.     

Spatial characteristics of radiation from lightning discharges

The results of measurements of levels of electric and magnetic radiation fields from lightning discharges are presented. Lightning discharges occurred in the region of the terrestrial surface bounded by a sector of ∼90° with a radius of ∼30–300 km. A power spatial dependence of the electromagnetic radiation field components of lightning discharges is established. The results of measurements are interpreted using fractal geometry methods.     

Erratum and addendum to “Transcranial stimulability of phosphenes by long lightning electromagnetic pulses” [Phys. Lett. A 374 (2010) 2932]

The comparison of electric fields transcranially induced by lightning discharges and by TMS brain stimulators via is shown to be inappropriate. Corrected results with respect to evaluation of phosphene stimulability are presented. For average lightning parameters the correct induced electric fields appear more than an order of magnitude smaller. For typical ranges of stronger than average lightning currents, electric fields above the threshold for cortical phosphene stimulation can be induced only for short distances (order of meters), or in medium distances (order of 50 m) only for pulses shorter than established axon excitation periods. Stimulation of retinal phosphene perception has much lower threshold and appears most probable for lightning electromagnetic fields.     

Electron band structure detection by high-order optical harmonic generation in solids

As the threshold field strength for the breakdown in air significantly exceeds the maximum measured thundercloud strength 3 kV/cm/atm, the problem of lightning initiation remains unclear. According to the popular idea, lightning can be initiated from streamer discharges developed in the enhanced electric field in a vicinity of hydrometeors. To test the idea, we carry out numerical simulations of positive streamer development around charged water drops at air pressure typical at thundercloud altitudes and at different background fields, drop sizes and charges. With real drop sizes and charges, the electric field required for the streamer formation is stronger than the measured fields; therefore, second mechanism is required to amplify the local field.     

人工引发雷电先导-回击过程的电场变化特征

 2005年夏季在山东滨州进行了以人工引发雷电为主的综合观测实验，在负电场环境下，成功引发雷电5次，其中传统引发方式3次，空中引发方式2次。详细分析了双向先导-小回击过程和箭式先导-回击过程的垂直电场变化特征。结果表明：2次空中引发雷电的双向先导发展过程在地面60 m处产生的电场变化为4.70~14.60 kV/m，呈负向变化；在550 m处为0.11~0.16 kV/m，呈正向变化。利用60 m处的先导电场变化，估算双向先导电荷线密度分布的斜率为(1.2~3.8)×10^-7 C·m^-2。箭式先导-回击电场变化波形呈不对称V形，V形的底部对应先导的结束和回击的开始。60和550 m处的箭式先导电场几何平均值分别为17.80和1.20 kV·m^-1。随水平距离的增加，箭式先导电场以水平距离的-1.18次方衰减。     

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).     

Simulation of a solid-state cooler with electrocaloric elements

The dynamics of change in temperature at the edges of a layered structure consisting of one or more electrocaloric and heat-conducting elements in response to pulses of a periodic electric field has been studied with the use of the finite-element method. The possibility of using ceramic materials and (Ba,Sr)TiO₃ films as electrocaloric and heat-conducting elements of linear and radial cooling structures is considered. The difference between the temperatures at the center and periphery of the radial film microstructure with two interdigital circular electrode lines is 2.5 K. An increase in the number of lines and the electric field frequency leads to an increase of the thermal effect.     

Identification of lightning vulnerability points on complex grounded structures

The identification of the most vulnerable points on a given structure to be struck by lightning is an important issue on the design of a reliable lightning protection system. Traditionally, these lightning strike points are identified using the rolling sphere method, through an empirical correlation with the prospective peak return stroke current. However, field observations in Kuala Lumpur and Singapore have shown that the points where lightning flashes strike buildings also depend on the height and geometry of the structure. Since a lightning strike point is believed to be the place on a grounded structure where a propagating upward leader is first initiated, a physical leader inception model is used here to estimate the background electric field required to initiate a stable upward leader from the corners of some complex buildings. The computed location of the points from where leaders are incepted are compared with the damaged points on buildings struck by lightning. The observed lightning strike points coincide rather well with the corners of the buildings which are characterized by lower leader inception electric fields. Furthermore, it is found that the geometry of the buildings significantly influences the conditions necessary to initiate upward leaders and, therefore, the location of the most likely strike points.     

Modeling the development of the stepped leader of a lightning discharge

A stochastic-deterministic model is presented for the propagation of a downward-moving leader. Lightning formation is described by a stochastic growth of branching discharge channels which is determined by the electrostatic field. The dynamics of the electric field and of the charge distribution over the lightning structure are calculated deterministically. The model includes the initiation of lightning, a preliminary discharge in a cloud, the propagation of a downwardmoving stepped leader toward the earth, and the initiation and upward motion of a return stroke from the earth’s surface. Numerical execution of the model yields a dynamic picture of the development of the downward-moving leader and of the intracloud discharge structure. The effect of the charge density in the cloud and the parameters of the developing channels on the spatial-temporal, current, and charge characteristics of the stepped leader’s propagation are studied. The effect of free-standing structures on the distribution of points on the earth’s surface where lightning strikes is examined. Zh. Tekh. Fiz. 69, 48–53 (April 1999)     

Effect of orographic features on global atmospheric electrical parameters over 160 different places of United States

Global atmospheric electrical parameters like atmospheric conductivity, air-earth current density, electric field, and atmospheric potential have been estimated over different places of United States (US) assuming fair weather conditions. Results show that atmospheric electrical conductivity and current density increase with height from sea level, while electric field remains constant at all altitudes. The atmospheric potential, on the other hand, decreases in US orography. New best fit regression lines between the atmospheric electrical parameters and height from sea level have been examined for US orography in both clean and clear atmosphere.     

Mechanism of generation of runaway electrons in a lightning leader

A mechanism is analyzed of the electric field enhancement in a lightning leader up to the level permitting runaway of low-energy electrons. The ionization wave propagation in the preionized domain in front of the leader makes it possible to overcome the limitation imposed on the field intensity by transversal expansion of the leader front. By means of numerical simulations, it is demonstrated that, at the final stage of formation of a new leader step, generation of an electric field is possible in the channels of the streamer zone ahead of the new step with intensity sufficient for electron runaway and, consequently, for producing the X-ray and γ-ray pulses observed in correlation with the lightning leader steps.     

Generation of neutrons in giant upward atmospheric discharges

It has been shown that the efficiency of the reactions of the fusion of deuterons in the atmosphere is very low; therefore, nuclear fusion cannot be responsible for the generation of neutrons by lightning. The generation of neutrons in thunderstorm fields is attributed to photonuclear reactions in giant upward atmospheric discharges over thunderclouds.