1.Nanjing University of Information Science &2.Technology;3.Chinese Academy of Sciences
The lightning electric field signal recorded by ground-based lightning detection stations generally has a polarity reversal phenomenon, and the polarity reversal time of different stations is different. At present, this phenomenon is not clearly understood. The measurement principle of electric field change signal caused by lightning discharge is described in detail. Based on this, using broadband electric field and VHF radiation data, combined with the location results of lightning VHF radiation source, the characteristics and causes of polarity reversal of lightning electric field pulse is analyzed. Comparing multi-station data with an interval of 5 km, it is found that the electric field polarity reversal at different stations does not occur at the same time. And the polarity reversal is often accompanied by a decrease in pulse amplitude, which often results in pulse missing or time error increasing of arriving pulses during positioning. Using broadband electric field positioning and VHF radiation source positioning to complement each other, on the basis of obtaining refined three-dimensional positioning of lightning, it is found that the development direction change of the lightning channel head caused the polarity reversal phenomenon of the vertical electric field. The proximity or distance of the large amount of electric charges carried by the head of the main channel is the main reason for the pulse fluctuation of the ground vertical electric field change measurement device. For lightning detection stations with different orientations, the relative movement of the head of the main lightning channel is the main reason for the different timing of pulse polarity reversal at different detection stations. Aiming at the problem of decreased positioning efficiency caused by the polarity reversal phenomenon, this paper proposes a solution for Hilbert energy spectrum, which increases the number of lightning radiation sources located by about 9%.
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