Studying the influence of hydrometeors on discharge initiation from an artificial thunderstorm cell and the characteristics of its electromagnetic radiation
Keywords:
artificial thunderstorm cell, positive and negative polarity, hydrometeor array, lightning, cloud and channel discharges, electromagnetic radiation, wavelet analysis, spectral characteristicsAbstract
Results from experimental investigations aimed at studying the influence of hydrometeors on initiating discharge from an artificial thunderstorm cell having negative and positive polarity are presented. The spectral characteristics of electromagnetic radiation from the discharges generated with participation of hydrometeors are investigated using a wavelet analysis. It has been found that depending on the cloud polarity, hydrometeors may initiate the formation of cloud discharges, as well as channel and diffuse discharges between the cloud and ground. The effect the hydrometeor array location in the cloud-to-ground gap has on the discharge initiation probability and on the spectral pattern of its electromagnetic radiation is clarified. It has been found that with a positively charged cloud, the cloud discharge initiation probability reaches its maximum when a group of hydrometeors partially locates in the cloud, and with a negatively charged cloud, its maximum is reached when the array of hydrometeors locates near the cloud lower boundary. As regards the formation of channel discharges with participation of hydrometeors, the opposite tendency has been revealed. An analysis of the electromagnetic radiation spectrum has shown the following. The wavelet spectrum of a cloud discharge generated from a negatively charged thunderstorm cell with participation of hydrometeors contains a band of frequencies exceeding 1 GHz. It has also been found that in case of hydrometeor-initiated cloud discharges, the limiting frequencies and the frequencies corresponding to the maximal intensity that appear in the wavelet spectra of signals are significantly higher for a negatively charged cloud than they are for a positively charged cell. A similar tendency has been found for channel discharges formed between the cloud and ground with the participation of hydrometeors. Thus, if a thunderstorm cloud contains zones with a sufficiently high concentration of large hydrometeors, this may significantly modify the initiation and propagation of discharges formed inside the thunderstorm cloud and between the cloud and ground, as well as the spectrum of their electromagnetic radiation.
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