On the polarity and continuing currents in unusually large lightning flashes deduced from ELF events |
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| Institution: | 1. Institute of Ionosphere, National Center for Space Research and Technology, Almaty 050020, Kazakhstan;2. Institute for Physics, Southern Federal University, Rostov-on-Don 344090, Russia;3. Hacettepe University, Dept. of Electrical and Electronics Engineering, Ankara 06800, Turkey;1. School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Binshuixi Road 399, Xiqing District, Tianjin 300387, PR China;2. Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xinning Road 18, Chengxi District, Xining 810008, PR China;3. Hebei Yuanda Securities Investment Consulting Company Limited, Zhongshan Road 265, Changan District, Shijiazhuang 050010, PR China;4. Institute of Urban and Rural Construction, Agricultural University of Hebei, Bao Ding 071001, PR China;1. Department of Electrical Engineering, Faculty of Engineering, Menoufia University, 32511 Shebin El-Kom, Egypt;2. Electrical Power and Machines Department, Faculty of Engineering, Ain Shams University, Cairo, Egypt;1. Department of Applied Physics, S.V. National Institute of Technology, Surat 395007, India;2. Department of Geology and Space Science, Chungnam National University, Daejeon 305764, Republic of Korea;3. Department of Electrical Electronic and Systems Engineering, Universiti Kebangsaan, 43600, Malaysia;4. Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan;1. Department of Physiotherapy, School of Rehabilitation, Tehran University of Medical Sciences, Tehran, Iran;2. Department of Physical Medicine and Rehabilitation, School of Medicine, Iran University of Medical Sciences, Tehran, Iran |
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| Abstract: | An analysis of ELF events has enabled the magnitude and duration of the continuing currents in 274 unusually large lightning flashes to be estimated. An exponential decay model of the variation of the current moment of the source lightning stroke with time was fitted to the measured spectra using an optimisation algorithm. Of the events analysed, 212 were of positive polarity (i.e. the initial polarity of the electric field was positive) and 62 were negative. The average magnitude of the peak current moment for positive events was 5.1 × 107 Am with a standard deviation of 3.2 × 107 Am while that for negative events was 2.9 × 107 Am with a standard deviation of 0.6 × 107 Am. The average time constant T of our data set is 32 ms with a standard deviation of 6 ms for positive events and 26 ms with a standard deviation of 5 ms for negative events. Positive events are therefore associated with somewhat larger and more variable current moments and slightly longer continuing currents. We believe that these positive events are most likely to be produced by positive cloud to ground lightning. |
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