Lightning Sferics: Analysis of the Instantaneous Phase and Frequency Inferred From Complex Waveforms

Zhongjian Liu, Kuang Liang Koh, Andrew Mezentsev, Sven Erik Enno, Jacqueline Sugier, Martin Fullekrug

Research output: Contribution to journalArticle

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Abstract

Analysis of very low frequency lightning waveforms, or radio sferics, can contribute to research into lower ionosphere perturbations and the corresponding atmospheric chemistry. Lightning waveforms can also be characterized on the basis of their propagation distance from receivers in order to study radio wave propagation. A bank of average waveforms, that is, the waveform bank, <1,000 km with a spatial resolution of 10 km has been produced, based on the lightning waveforms recorded in Europe on 8 August 2014. These average lightning waveforms at different distances exhibit a sequence of consecutive maxima resulting from ionospheric reflections, named sky waves. The spectral waveform bank shows a sequence of consecutive modal maxima at different frequencies depending on distance. The Hilbert transform is applied to produce complex lightning waveforms, which provide additional information to the original real waveforms alone, that is, the instantaneous phase and frequency. The time differences calculated from the instantaneous phases of complex lightning waveforms give the minimum arrival time difference error when compared to other analyzed signal processing methods. The derivative of the instantaneous phase, that is, the instantaneous frequency, represents the amplitude-weighted average of frequency components at maximum amplitude according to theory and numerical simulation. In real experiments, the instantaneous frequency can be understood as the median value of the real frequency distribution calculated at maximum amplitude. It is found that the instantaneous frequencies at maximum amplitudes are distance dependent. This finding might enable the development of a novel method to determine lightning distances in the future.

LanguageEnglish
Pages448-457
JournalRadio Science
Volume53
Issue number4
Early online date24 Mar 2018
DOIs
StatusPublished - 1 Apr 2018

Fingerprint

lightning
Lightning
waveforms
Atmospherics
Atmospheric chemistry
Radio waves
sky waves
Ionosphere
radio wave
atmospheric chemistry
signal processing
ionospheric propagation
arrival time
analysis
Wave propagation
wave propagation
lower ionosphere
ionosphere
very low frequencies
Signal processing

Keywords

  • Atmospheric and space electricity
  • Complex waveform
  • Instantaneous frequency
  • Instantaneous phase
  • Lightning discharge
  • Sferics

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Earth and Planetary Sciences(all)
  • Electrical and Electronic Engineering

Cite this

Lightning Sferics : Analysis of the Instantaneous Phase and Frequency Inferred From Complex Waveforms. / Liu, Zhongjian; Koh, Kuang Liang; Mezentsev, Andrew; Enno, Sven Erik; Sugier, Jacqueline; Fullekrug, Martin.

In: Radio Science, Vol. 53, No. 4, 01.04.2018, p. 448-457.

Research output: Contribution to journalArticle

Liu, Zhongjian ; Koh, Kuang Liang ; Mezentsev, Andrew ; Enno, Sven Erik ; Sugier, Jacqueline ; Fullekrug, Martin. / Lightning Sferics : Analysis of the Instantaneous Phase and Frequency Inferred From Complex Waveforms. In: Radio Science. 2018 ; Vol. 53, No. 4. pp. 448-457
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