INTRACLOUD LIGHTNING DISCHARGES IN THE LOWER PART OF THUNDERCLOUD

From analysis of observational data of thunderstorms in Gansu,China,it was deduced that the electric structure of thunderclouds in this region is often positive charge in the upper,main negative in the middle layer and another positive charge,large in magnitude and extensive in dimension,in the lower part.Intra- cloud discharges often take place between the main negative charge and lower positive charge instead of upper. Case analysis of 6 intracloud discharges in two storms on August 3 and 4,1986 shows that the centers of these discharges and the dipole moments destroyed were at the altitude of 3.8—6 km msl(7.6—-13.5℃)and 18— 40 C km,respectively.

Research on Characteristic Parameters of Lightning Discharge Channels Based on Spectrum

According to the time-resolved spectra of lightning return stroke process and based on the plasma transmission theory,the evolution characteristics of the thermal conductivity and thermal diffusion coefficient of the discharge channel over time during the lightning return stroke are discussed.The radial distribution of the channel temperature in the lightning peak current phase is calculated,and the heat transfer along the radial direction of the channel is analyzed.The calculated transmission characteristic parameter values of the lightning discharge channel are all in a reasonable range.The results show that the heat transport coefficient of the lightning channel is closely related to the channel temperature and electron density.After returning to the peak current,the channel temperature slowly decreases,and the transport coefficient shows a non-linear and monotonous decay trend.The closer to the current core channel is,the greater the temperature gradient is,and the more the heat transferred radially outward is.

About Resolvability of the Problem of Lightning Coordinates Finding by the Time of Lightning Discharge Arrival

On the unit sphere, the geometric problem of calculating the position of a point relative to three given points is considered. We know the length of three spherical segments that go out from the given points in the direction of the unknown point. The requirement must be fulfilled: the distance from each point to an unknown point must be equal to the sum of the length of the segment outgoing from this point, and some increment, the same for all three segments. In the article, the conditions for the solvability of a geometric problem are established by the methods of spherical trigonometry and vector algebra. It is proved that when they are fulfilled, the problem is always solvable. The number of solutions is two, except in rare cases where there is only one solution. A solution method is presented. One of the practical applications is the problem of determining the time and location of a cloud-to-ground lightning discharge, which is directly reduced to this problem.

Development of a Lightning Warning System

A lightning warning system （LWS） which can predict the possibility of lightning strike and the position of lightning discharge was developed. The LWS uses the electric field intensity at the ground as a parameter to warn the possibility of lightning strikes. A planar shutter type electric field mill （EFM） with a rotating vane is studied to measure the electric field. From a calibration experiment, the sensitivity of the EFM was adjusted to 0.15 V/kV/m, and this covers the ranges from 200 V/m to 20 kV/m. Magnetic field waveform is detected by a crossed loop coil and an integral amplifier. Frequency bandwidth of the circuit ranges from 5 kHz to 1.2 MHz. The polarity of lightning discharges is discriminated by electric field component. After fixing the polarity, we can calculate the direction and distance of lightning discharge by the peak and the zero cross time of the detected magnetic field waveform.

Variations of Atmospheric ELF/VLF Radio Noise Due to Seismogenic Modifications in Tropospheric Conductivity

We suggest a possible explanation of the influence of pre-seismic activity on the registration rate of natural ELF(extremely low frequency)/VLF(very low frequency) pulses and the changes of their characteristics. The main idea is as follows. The distribution of the electric field around a thundercloud depends on the conductivity profile of the atmosphere. Quasi-static electric fields of a thundercloud decrease in those tropospheric regions where an increase of air conductivity is generated by pre-seismic activities due to emanation of radioactive gas and water into the lower atmosphere. The electric field becomes reduced in the lower troposphere, and the probability decreases of the cloud-to-ground (CG) strokes in such “contaminated” areas. Simultaneously, the electric field grows inside and above the thunderclouds, and hence, we anticipate a growth in the number of horizontal and tilted inter-cloud (or intra-cloud) (both termed as IC discharges) strokes. Spatial orientation of lightning strokes reduces vertical projection of their individual amplitudes, while the rate (median number strokes per a unit time) of discharges grows. We demonstrate that channel tilt of strokes modifies the spectral content of ELF/VLF radio noise and changes the rate of detected pulses during the earthquake preparation phase.

Integral Transformation of the Pulse Function for High Voltage Technique

One function for approximating pulse quantities in high voltage technique is presented in this paper. The function derivative, its integral, as well as its Laplace and Fourier transform are obtained analytically. Integral transformations of the pulse function are needed in frequency domain calculations of lightning induced effects in the case of a lossy ground. The pulse function having adequately chosen parameters is applied in lightning discharge modeling for lightning electromagnetic field calculation, and the results are in agreement with the results from literature. The choice of function parameters is based on their influence on the pulse waveshape which is presented in the paper. Numerical results for the Fourier transform are presented for different usually used pulse functions. The advantages of this function are simple choice of its parameters according to the desired waveshape characteristics and analytical solutions useful in lightning discharge modeling, electromagnetic field computation and induced effects calculations.