Breakdown conditions and thermal instability in air

Summary Reduced electric fields (E/N) responsible for electrical breakdown in air have been calculated by solving a stationary Boltzmann equation including superelastic vibrational collisions. The results show a decrease ofE/N with increasing gas temperature. The possibility of air instability due to chemical processes producing electrons is then investigated by calculating the threshold of this instability as a function of a characteristic time for heat dissipation τ.     

Breakdown in air in a rising microwave field

Results are presented from studies of a high-pressure electrodeless breakdown in air at the focus of a standing wave in a high-Q quasi-optical two-mirror resonator pumped by single microwave pulses. In the experiment, the breakdown occurred at the front of the pulse of the resonator field. The breakdown field substantially exceeded the critical level and, under fixed conditions, showed a scatter from pulse to pulse. It is shown that the experimentally found excess in the threshold breakdown field over the critical level is due to the fact that the resonator field increases as a discharge plasmoid forms during breakdown and that the appearance of an electron initiating breakdown in a gas is a random event.     

Disturbances of the upper atmosphere and ionosphere caused by acoustic-gravity wave sources in the lower atmosphere

The results of observations of acoustic-gravity waves in the troposphere and the ionosphere at middle latitudes during periods of passage of the solar terminator are presented. Tropospheric observations were performed using a lidar. The frequency characteristics of variations of the tropospheric parameters are determined based on observations of the intensity of the scattered lidar signal. The characteristics of variations of the total electron content (TEC) in the atmosphere are determined from data collected by GPS navigation satellites. An analysis of the observational data showed that the spectrum of variations of the atmospheric and ionospheric parameters is indicative of acoustic-gravity waves (AGW) propagating from the lower atmosphere. Modeling studies of the vertical propagation of AGW from the Earth’s surface showed that such waves quickly (within ~15 min) reach altitudes of the upper atmosphere (~300 km). The refraction and dissipation of waves in the upper atmosphere produces perturbations of the background state of the atmosphere and gives rise to the waveguide propagation of infrasonic wave components. The observed manifestations of TEC disturbances caused by AGW propagating from the lower atmosphere can be explained by the diurnal variation of the altitude of the ionosphere and the waveguide propagation of infrasonic waves.     

LIDAR monitoring of the temperature in the middle and lower atmosphere

Two methods are described to monitor the temperature of the atmosphere from the ground to 100 km altitude. The Rayleigh LIDAR is now widely used (the French network includes four of those characteristics of which are given), and here, the major results obtained from this technique are presented. The second method, which completes the Rayleigh LIDAR downwards, uses the rotational Raman lines of O₂ and N₂. The method is briefly described and first results are presented. Including both the Rayleigh and Raman modes leads to a continuous temperature measuring method to survey changes in the lower and middle atmosphere.     

激光大气闪烁的分形分析

 采用分形理论分析了激光大气闪烁的统计特征。研究结果表明：在弱起伏条件下，激光大气闪烁的分形维和奇异性随光强起伏的增强而增大，而其长期相关性则减小；不同Fresnel尺度下具有相同闪烁指数的激光大气闪烁的分形特征存在着明显的差别；在强起伏条件下，有限的数据中尚未发现分形维有饱和现象，因此可以用来描述激光大气闪烁的强度。     

激光大气闪烁的分形分析

采用分形理论分析了激光大气闪烁的统计特征。研究结果表明：在弱起伏条件下,激光大气闪烁的分形维和奇异性随光强起伏的增强而增大,而其长期相关性则减小;不同Fresnel尺度下具有相同闪烁指数的激光大气闪烁的分形特征存在着明显的差别;在强起伏条件下,有限的数据中尚未发现分形维有饱和现象,因此可以用来描述激光大气闪烁的强度。     

Simulation of the coupling of the upper and lower atmosphere

The coupling of the upper and lower atmosphere and the problem of developing a unified numerical model of the Earth’s gaseous envelope is considered. The existing models of the upper and lower atmosphere are analyzed and specific models for use as parts of a future metamodels of Earth’s atmosphere are selected. A general algorithm for combining these models is proposed.     

重复频率纳秒脉冲聚四氟乙烯薄膜击穿特性

实验研究了聚四氟乙烯薄膜在重复频率纳秒脉冲下的击穿特性,选用脉冲上升时间约15 ns,脉宽30~40 ns,重复频率1~1 000 Hz。测量并计算了击穿前后的电压电流波形、重复频率耐受时间和施加脉冲个数与击穿特性密切相关的参数。结果表明,重复频率纳秒脉冲下聚四氟乙烯薄膜击穿场强为MV/cm量级,重复频率耐受时间随施加场强和重复频率的增大而减小。薄膜本身性质及油浸时间使实验数据具有分散性,重复频率纳秒脉冲下聚四氟乙烯薄膜击穿应考虑重复频率条件下的热积累效应和材料缺陷。     

重复频率纳秒脉冲聚四氟乙烯薄膜击穿特性

实验研究了聚四氟乙烯薄膜在重复频率纳秒脉冲下的击穿特性,选用脉冲上升时间约15 ns,脉宽30~40 ns,重复频率1~1 000 Hz。测量并计算了击穿前后的电压电流波形、重复频率耐受时间和施加脉冲个数与击穿特性密切相关的参数。结果表明,重复频率纳秒脉冲下聚四氟乙烯薄膜击穿场强为MV/cm量级,重复频率耐受时间随施加场强和重复频率的增大而减小。薄膜本身性质及油浸时间使实验数据具有分散性,重复频率纳秒脉冲下聚四氟乙烯薄膜击穿应考虑重复频率条件下的热积累效应和材料缺陷。     

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.     

Ionization process in the humid air of the lower troposphere

This paper analyzes the local processes of ionization and electron loss in the early stages of an electric discharge in humid air at altitudes of 0–12 km. The processes of ionization in an external electric field, background ionization, attachment and detachment of electrons from atomic and molecular oxygen, charge transfer, and the conversion of negative ions are considered. The dependences of the rate constants on the pressure are taken into account. It is shown that the electric field strength at which the effective ionization of air begins decreases with increasing altitude.     

Some aspects of the solar cyclicity display in the lower atmosphere of the Earth

Several examples of the solar cyclicity display in the lower atmosphere and in the ocean are considered using the North Atlantic as an illustration. The solar activity is manifested by the increased recurrence of certain circulation forms.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 39, No. 10, pp. 1342–1347, October, 1996.     

Remote sensing of thermal profile in the lower atmosphere by a radio-acoustic system

Summary A new radio-acoustic methodology, for the remote sensing of temperature profile in the lower troposphere, has been developed in the last few years. Since 1972 different types of radio-acoustic sounders have been designed and tested in the USA, Europe and Japan. The technique used for measurements in a Doppler tracking of a short acoustic pulse with a radar. Measurement of the sound speed as a function of delay from the start of the acoustic beam leads to the acquisition of the temperature vertical profile. After a brief review of the experimental radio-acoustic systems, the metric radio-acoustic sounder developed and tested at Istituto di Cosmogeofisica of the National Research Council (Italy) is analysed. Results of this sounder and its performance in fog-capping thermal inversion measurements are discussed. A comparison of the data measured with the radio-acoustic system and with traditional methods shows:a) sounder ability to produce vertical thermal profile with temperature accuracy and height discrimination comparable with conventional soundings;b) advantages typical of remote-sensing technique;c) applicability of the system both in assessing thermodynamic conditions in the planetary boundary layer (PBL) and in sensing conditions conductive to high concentrations of air pollutants at ground level. Preliminary results of the completely automatized system and application to air quality management are also presented. This work was partially supported by the Commission of the European Communities (CEC) under contract No. ENV·348 I(S) and by a research contract by ENEL-CRTN Milano.     

微秒脉冲下碳酸丙烯酯的击穿特性

采用紧凑Tesla变压器型脉冲功率驱动源及球电极击穿试件,通过改变初级充电电压,开展了微秒级充电条件下碳酸丙烯酯及其与碳酸乙烯酯的混合液的击穿实验研究。由结果和分析可知：碳酸丙烯酯理论工作温度可低至-55 ℃,这意味着它可以成为一种低温下的良好液体电介质;碳酸丙烯酯耐压性能与去离子水相当,且实测电阻率达到了10 Mcm以上;向碳酸丙烯酯中添加碳酸乙烯酯后,介电常数可提高至80以上,耐压强度也有所提升;将碳酸丙烯酯、碳酸乙烯酯/碳酸丙烯酯混合液用于脉冲形成线作为储能介质无需附加去离子处理系统,有利于装置的紧凑化和小型化。     

微秒脉冲下碳酸丙烯酯的击穿特性

采用紧凑Tesla变压器型脉冲功率驱动源及球电极击穿试件,通过改变初级充电电压,开展了微秒级充电条件下碳酸丙烯酯及其与碳酸乙烯酯的混合液的击穿实验研究。由结果和分析可知:碳酸丙烯酯理论工作温度可低至-55℃,这意味着它可以成为一种低温下的良好液体电介质;碳酸丙烯酯耐压性能与去离子水相当,且实测电阻率达到了10 MΩ·cm以上;向碳酸丙烯酯中添加碳酸乙烯酯后,介电常数可提高至80以上,耐压强度也有所提升;将碳酸丙烯酯、碳酸乙烯酯/碳酸丙烯酯混合液用于脉冲形成线作为储能介质无需附加去离子处理系统,有利于装置的紧凑化和小型化。     

大气环境下用于瞄准的激光波束传播特性研究

针对激光瞄准过程中的光斑偏移现象,结合修正的Von Karman谱的折射指数起伏和Hufnagel-Vally湍流模型上的近似积分,研究了高斯脉冲光束在湍流大气中远场水平以及斜程传播时的脉冲展宽和闪烁指数,分析了强湍流条件下1.06 μm准单色光斜程大气传输光强分布与脉冲展宽的关系,对数值结果进行比较,发现远距离传输中波长和距离对波束瞄准偏差影响较大.从理论和实验上对大气环境下激光光斑瞄准偏差进行了分析研究,研究结果表明:将激光光斑全场数据及分析结果应用到现有偏差补偿算法中,可以实现激光瞄准偏差的有效补偿,在大气能见度1 km～3 km范围内,激光瞄准偏差测量误差σA≤0.1 mrad.     

High energy physics in the atmosphere: phenomenology of cosmic ray air showers

The properties of cosmic rays with energies above 10⁶ GeV have to be deduced from the spacetime structure and particle content of the air showers which they initiate. In this review we summarize the phenomenology of these giant air showers. We describe the hadronic interaction models used to extrapolate results from collider data to ultra high energies, and discuss the prospects for insights into forward physics at the LHC. We also describe the main electromagnetic processes that govern the longitudinal shower evolution, as well as the lateral spread of particles. Armed with these two principal shower ingredients and motivation from the underlying physics, we provide an overview of some of the different methods proposed to distinguish primary species. The properties of neutrino interactions and the potential of forthcoming experiments to isolate deeply penetrating showers from baryonic cascades are also discussed. We finally venture into a terra incognita endowed with TeV-scale gravity and explore anomalous neutrino-induced showers.     

纳秒脉冲电压下气体开关的击穿特性

采用快速Marx发生器产生ns量级的高电压脉冲,分别开展了不同脉冲电压值下气体开关自击穿实验,获得了气体开关在不同气压下的击穿电压和击穿延迟时间以及抖动。详细介绍了纳秒脉冲电压作用下,气体火花开关击穿电压和击穿延迟时间随工作气压变化的特点,指出了气体开关在不同场合应用时的要求。     

纳秒脉冲下单间隙伪火花放电特性

采用单间隙伪火花放电装置,研究了纳秒脉冲下气压、间隙距离和小孔直径对伪火花放电特性的影响。研究结果表明,纳秒脉冲下伪火花放电电压随着气压、间隙距离和小孔直径的增加而减小。通过数值拟合,得到了放电电压与气压、间隙距离和小孔直径间的经验公式。放电电压随着气压、间隙距离和小孔直径的增加而减小,衰减系数分别为0.76,0.39和0.39。