Physical mechanism of initial breakdown pulses and narrow bipolar events in lightning discharges

Caitano L. Da Silva, Victor P. Pasko

    Research output: Contribution to journalArticle

    25 Scopus citations

    Abstract

    To date the true nature of initial breakdown pulses (IBPs) and narrow bipolar events (NBEs) in lightning discharges remains a mystery. Recent experimental evidence has correlated IBPs to the initial development of lightning leaders inside the thundercloud. NBE wideband waveforms resemble classic IBPs in both amplitude and duration. Most NBEs are quite peculiar in the sense that very frequently they occur in isolation from other lightning processes. The remaining fraction, 16% of positive polarity NBEs, according to Wu et al. (2014), happens as the first event in an otherwise regular intracloud lightning discharge. These authors point out that the initiator type of NBEs has no difference with other NBEs that did not start lightning, except for the fact that they occur deeper inside the thunderstorm (i.e., at lower altitudes). In this paper, we propose a new physical mechanism to explain the source of both IBPs and NBEs. We propose that IBPs and NBEs are the electromagnetic transients associated with the sudden (i.e., stepwise) elongation of the initial negative leader extremity in the thunderstorm electric field. To demonstrate our hypothesis a novel computational/numerical model of the bidirectional lightning leader tree is developed, consisting of a generalization of electrostatic and transmission line approximations found in the literature. Finally, we show how the IBP and NBE waveform characteristics directly reflect the properties of the bidirectional lightning leader (such as step length, for example) and amplitude of the thunderstorm electric field.

    Original languageEnglish (US)
    Pages (from-to)4989-5009
    Number of pages21
    JournalJournal of Geophysical Research
    Volume120
    Issue number10
    DOIs
    StatePublished - 2015

    All Science Journal Classification (ASJC) codes

    • Geophysics
    • Forestry
    • Oceanography
    • Aquatic Science
    • Ecology
    • Water Science and Technology
    • Soil Science
    • Geochemistry and Petrology
    • Earth-Surface Processes
    • Atmospheric Science
    • Earth and Planetary Sciences (miscellaneous)
    • Space and Planetary Science
    • Palaeontology

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