A detailed investigation of low latitude tweek atmospherics observed by the WHU ELF/VLF receiver:Ⅰ. Automatic detection and analysis method  

作　　者：RuoXian Zhou XuDong Gu KeXin Yang GuangSheng Li BinBin Ni Juan Yi Long Chen FuTai Zhao ZhengYu Zhao Qi Wang LiQing Zhou 

机构地区：[1]Department of Space Physics,School of Electronic Information,Wuhan University,Wuhan 430072,China [2]State Key Laboratory of Space Weather,Chinese Academy of Sciences,Beijing 100190,China

出　　处：《Earth and Planetary Physics》2020年第2期120-130,共11页地球与行星物理（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grants Nos. 41674163, 41474141, 41204120, 41304127, 41304130, and 41574160);the Projects funded by China Postdoctoral Science Foundation (Grants Nos. 2013M542051, 2014T70732);the Hubei Province Natural Science Excellent Youth Foundation (2016CFA044);the Project Supported by the Specialized Research Fund for State Key Laboratories;the 985 funded project of School of Electronic information, Wuhan University

摘　　要：As a dispersive wave mode produced by lightning strokes, tweek atmospherics provide important hints of lower ionospheric(i.e., D-region) electron density. Based on data accumulation from the WHU ELF/VLF receiver system, we develop an automatic detection module in terms of the maximum-entropy-spectral-estimation(MESE) method to identify unambiguous instances of low latitude tweeks.We justify the feasibility of our procedure through a detailed analysis of the data observed at the Suizhou Station(31.57°N, 113.32°E) on17 February 2016. A total of 3961 tweeks were registered by visual inspection;the automatic detection method captured 4342 tweeks, of which 3361 were correct ones, producing a correctness percentage of 77.4%(= 3361/4342) and a false alarm rate of 22.6%(= 981/4342).A Short-Time Fourier Transformation(STFT) was also applied to trace the power spectral profiles of identified tweeks and to evaluate the tweek propagation distance. It is found that the fitting accuracy of the frequency–time curve and the relative difference of propagation distance between the two methods through the slope and through the intercept can be used to further improve the accuracy of automatic tweek identification. We suggest that our automatic tweek detection and analysis method therefore supplies a valuable means to investigate features of low latitude tweek atmospherics and associated ionospheric parameters comprehensively.As a dispersive wave mode produced by lightning strokes, tweek atmospherics provide important hints of lower ionospheric(i.e., D-region) electron density. Based on data accumulation from the WHU ELF/VLF receiver system, we develop an automatic detection module in terms of the maximum-entropy-spectral-estimation(MESE) method to identify unambiguous instances of low latitude tweeks.We justify the feasibility of our procedure through a detailed analysis of the data observed at the Suizhou Station(31.57°N, 113.32°E) on17 February 2016. A total of 3961 tweeks were registered by visual inspection; the automatic detection method captured 4342 tweeks, of which 3361 were correct ones, producing a correctness percentage of 77.4%(= 3361/4342) and a false alarm rate of 22.6%(= 981/4342).A Short-Time Fourier Transformation(STFT) was also applied to trace the power spectral profiles of identified tweeks and to evaluate the tweek propagation distance. It is found that the fitting accuracy of the frequency–time curve and the relative difference of propagation distance between the two methods through the slope and through the intercept can be used to further improve the accuracy of automatic tweek identification. We suggest that our automatic tweek detection and analysis method therefore supplies a valuable means to investigate features of low latitude tweek atmospherics and associated ionospheric parameters comprehensively.

关 键 词：tweeks automatic detection WHU-VLF receiver 

分 类 号：P352[天文地球—空间物理学]