Observation And Study Of Lightning Chaotic Leader

In this paper, a special class of leader process-dart chaotic leader is investigated. In order to get the integrated features of the dart chaotic leader, a number of test data by the summer of2013field observations collected. We explore and give the Characterization of the chaotic and the methods of the time-frequency domain analysis based on the comparative and comprehensive analysis of the observational data.The main conclusions in this paper are as follows:(1) A multi-scale entropy method is proposed to analyze the lightning electric field data of fast changes. As a characteristic parameters, the multi-scale entropy can be used to distinguish the dart chaotic leader and the other leader processes. Especially when the scale is greater than3, the three leader can be clearly distinguished by its entropy value. The process with the entropy value greater than1.5may be classified as a chaotic leader, and the one with the entropy value less than1.5is classified as a stepped leader or a dart leader.(2) Dart chaotic leaders can be classified into two categories according to the fast electric changes data. Through the statistical analysis of each type, we concluded that the probability of the occurrence of the first type of dart chaotic leader can reach81%, and the second type is only19%. We also give the sample entropy feature of the two types of dart chaotic leader. Through the comparative analysis of two kinds of chaotic leaders, we discover that the first dart chaotic leader’s sample entropy increases slightly with time, while the second dart chaotic leader’s sample entropy increases at first but then decreases with time. (3) Time-frequency feature of the dart chaotic leader, dart stepped leader and dart leader are analyzed by using the method of wavelet analysis. Our analysis shows that between10MHz and300MHz, the electromagnetic radiation energy of the dart chaotic leader is stronger than the other two leaders’, in particular, the energy of dart leader is significantly smaller than the other two leaders’, and all of the three leaders’ electromagnetic radiation energy decreases with the increase of frequency. The attenuation rate in10-50MHz is larger than that in50MHz～300MHz.(4) The optical characteristics of the second type of dart chaotic leader are summarized combined with the integrated observation. We find that the chaotic pulse occurs, accompanies the variousness of the optical signal. By analyzing the speed camera data, we find that the time when chaotic pulse occurs corresponds to the high-speed camera images in the discharge process deviating from the original pilot channel. So it can be concluded that the second type of dart chaotic leader may be caused by the attempted leader.The comprehensive observation brings us more information in analysis of dart chaotic leader process, and helps to deepen the understanding of the physical mechanism of such discharge process.