Wavelet‐Based Multifractal Analysis of the Radiation Field of First Return Stroke in Cloud‐To‐Ground Discharge

By using electric field change data obtained during the summer of 2002 in Qinghai province, the detection of radiation fields of the first return stroke involving in negative cloud-to-ground lightning discharges and their multifractal behaviors were analyzed with Wavelet Transform Modulus Maxima (WTMM) method. It was indicated that the variation coefficient of wavelet coefficients at the lower level of decomposition exhibits a sharp peak just at the position of main pulse peak of return stroke (return stroke point), thus the return stoke points can be reliably and effectively detected. It was also found that radiation field of the first return stroke exhibits strong multifractality, all scaling behavior is consisted with a modified version of the binomial multiplicative cascade multifractal model, and two characteristic parameters, the width of spectrum and the minimum spectral exponent were obtained with mean of 1.5 and –0.11, respectively. We suggest that the wavelet and multifractal method is a powerful tool in lightning signal's detection and reorganization.