Inversion Of Cloud-to-ground Lightning Current And Its Characteristics

In thunderstorm activity, the cloud-to-ground （CG） lightning discharge process isone of the most influential and destructive phenomena on human production andliving. However, its own Semi-random, dispersion, suddenness and transient makes itdifficult to accurately capture and directly observe.The electromagnetic data is used to calculate the two major discharge processesof CG lightning, including return stroke and M component. In the meantime, therelated contrast, analysis and verification results are also showed in this work. Themain contents and conclusions are as below:1、Starting from design principle of the electric field instrument, the simplest andmost feasible program is used to improve the measuring range of the electric fieldinstrument.2、Discussing the retrieval method of return stroke current. Based on the researchof calculating stroke peak current by using long distance-range electromagnetic field,the Maxwell’s equations are simplified according to the suitable physical model. Theelectromagnetic field data, which was measured about2km distance from thetriggered lightning channel got in Conghua, Guangzhou, is used to calculate in theinversion process of strokes current waveform. Simultaneously, the calculation resultsare compared with the real waveform of channel base current measured by coaxialshunt. Particularly focusing on the comparison of the amplitude and geometrycharacteristic of the waveform parameters between them. The result showed that thiscalculation method can inverse the Conghua Guangzhou triggered lightning’s returnstroke current waveform.3、Discussing the retrieval method of current of M component. According to thedata of channel base current and close electromagnetic field in the triggered lightningobtained in Conghua, Guangzhou during the period of2008-2010, the characteristicsand correlations of base current and electromagnetic field of M component are analyzed. The results show that: a) the geometric mean values of duration,10%-90%rise time, decline time and half-peak width for electric field waveform of Mcomponent are0.49ms,0.12ms,0.28ms and0.15ms, respectively; b) the geometricmean values of duration,10%-90%rise time, decline time, half-peak width and peakfor current waveform of M component are0.53ms,0.11ms,0.31ms,0.17ms and0.34kA; c) the geometric mean values of duration,10%-90%rise time, decline time,half-peak width and peak for magnetic field waveform of M component are0.65ms,0.16ms,0.37ms,0.21ms and2.76×10^-5T.The correlation analysis showed that, not only the geometry is more consistent,and there is a certain mutual relationship on the waveform of current, electric fieldand magnetic field waveform of M component. Furthermore, there is a relativelystrong correlation between the peaks of current and electromagnetic field waveform.According to the relationship between the electromagnetic field and the current,giving the equations base on electromagnetic data to inversion the peak current of Mcomponent. As a result, it is feasible to calculate the current waveform of Mcomponent by using the electromagnetic field data. The formula for calculating thepeak current of M component based on the electromagnetic data is proposedaccording to the relationship between the electromagnetic field and with the current.