基于MF-DFA的极低频瞬态事件多重分形分析

利用三个测站实测极低频全球闪电活动背景信号南北及东西方向磁场分量资料, 应用多重分形方法对极低频瞬态事件发生时前1s背景信号中的长程关联性及多重分形特征进行了分析. 发现极低频瞬态事件发生时, 最大脉冲前1s背景信号南北及东西方向磁场均具有长程关联性和多重分形特征. 其中南北方向最小标度指数0.15 < a_min< 0.22, 分形谱宽度1.09 < Δa < 1.51; 东西方向最小标度指数0.23 < a_min< 0.59, 分形谱宽度0.75 < Δa < 0.99. 多重分形谱参数Δa和a_min可以很好地自动识别Q-burst发生. 

Multifractal Analysis of ELF Transient Events Based on MF-DFA

In this paper, the magnetic field components totally continued 10 seconds using measured ELF global lightning activity background signal. The measuring signal sensor includes a pair of horizontal antenna which are orthogonal to each other and a spherical antenna with vertical placement. The horizontal antenna is for receiving ELF horizontal magnetic (HNS, HEW) signal of north-south and east-west directions, while the vertical antenna is for receiving ELF vertical electric field signal. By using the magnetic field component in both north-south and east-west direction of the observational extremely low frequency background signal of global lightning activity, and based on MF-DFA (Multifractal Detrended Fluctuation Analysis) multiple fractal method to analyze the long range correlation and multiple fractal characteristic of the background signal one second before the Q-burst occurs. Then, it is found that the magnetic field in the north-south, east-west direction of the maximum impulse one second before the Q-burst occurs has a long range correlation and multiple fractal characteristics. Among them, the minimum scaling exponent of the north-south direction is 0.15 < a_min < 0.22, fractal spectrum width is 1.09 < Δa < 1.51; the minimum scaling exponent of the east-west direction is 0.23 < a_min < 0.59, fractal spectrum width is 0.75 < Δa < 0.99. The multiple fractal spectrum parameters Δa, a_min can automatically identify the occurrence of Q-burst excellently.