Fractal Model of a Compact Intracloud Discharge. I. Features of the Structure and Evolution

Иудин, Д. И.; Davydenko, S. S.

doi:10.1007/s11141-015-9621-2

Cited by 15 publications

(11 citation statements)

References 52 publications

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“…In this study, we assume a factor of 2 different threshold fields for positive (superscript “+”) and negative (superscript “‐”) polarities:

E_{i t h}^{+} = 1.34 MV false/ normalm

E_{i t h}^{-} = 2.68 MV false/ normalm

E_{p t h}^{+} = 0.31 MV false/ normalm

, and

E_{p t h}^{-} = 0.62 MV false/ normalm

at an altitude of 1 km, which corresponds to the height of our computational domain center above ground level. Similar streamer propagation fields were obtained experimentally by Allen and Mikropoulos () and theoretically estimated by Gallimberti et al () for positive polarity and adopted for both polarities in a number of lightning development models (Iudin & Davydenko, ; Iudin et al, , ; Mansell et al, , Tan et al, ). Note that in this study

E_{i t h}^{+}

and

E_{i t h}^{-}

apply only to the initiation of first collective streamer from the node representing the space stem and that, because of

E_{i t h}^{-} > E_{i t h}^{+}

, the first streamer is always positive and, hence,

E_{i t h}^{-}

is not needed in modeling the initiation of streamers from the space stem.…”

Section: Model Descriptionsupporting

confidence: 84%

“…All presently existing numerical models describing lightning discharge development (see, e.g., Davydenko & Iudin, 2016;Iudin & Davydenko, 2015;Iudin et al, , 2017Mansell et al, 2002Mansell et al, , 2010Riousset et al, 2007;Tan et al, 2006;Wang et al, 2016) do not consider the difference in fields required for propagation of positive and negative streamers. This polarity asymmetry is well known from laboratory spark studies, which indicate that the fields in streamer zones of positive and negative leaders, which are approximately constant, differ by about a factor of 2 and are equal to about 5 and 10 kV/cm, respectively (Gorin & Shkilev, 1976;Raizer, 2009, p. 596).…”

Section: Appendix A: Polarity Asymmetrymentioning

confidence: 99%

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Numerical Simulation of Stepping and Branching Processes in Negative Lightning Leaders

et al. 2020

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A numerical model with physical timing and grid spacing of 3 m is applied to studying the progression (including stepping and branching) of negative lightning stepped leader. The asymmetry between positive and negative streamers is taken into account via using polarity‐dependent initiation and propagation field thresholds. The stepped nature of negative leader is confirmed to be caused by this asymmetry. The step formation process of the negative leader is modeled to begin with the appearance of space stems inside and in the immediate vicinity of its streamer zone (corona streamer burst completing the preceding step). Some of those space stems evolve into space leaders, which can connect to the primary leader channel, thereby facilitating its extension. Model‐predicted morphology and dynamics of negative leaders are in good agreement with the recent recordings of lightning stepped and dart‐stepped leaders obtained using high‐speed video cameras, and their electrical parameters are in line with the current knowledge on negative lightning leaders.

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“…In this study, we assume a factor of 2 different threshold fields for positive (superscript “+”) and negative (superscript “‐”) polarities:

E_{i t h}^{+} = 1.34 MV false/ normalm

E_{i t h}^{-} = 2.68 MV false/ normalm

E_{p t h}^{+} = 0.31 MV false/ normalm

, and

E_{p t h}^{-} = 0.62 MV false/ normalm

E_{i t h}^{+}

and

E_{i t h}^{-}

apply only to the initiation of first collective streamer from the node representing the space stem and that, because of

E_{i t h}^{-} > E_{i t h}^{+}

, the first streamer is always positive and, hence,

E_{i t h}^{-}

is not needed in modeling the initiation of streamers from the space stem.…”

Section: Model Descriptionsupporting

confidence: 84%

Section: Appendix A: Polarity Asymmetrymentioning

confidence: 99%

Numerical Simulation of Stepping and Branching Processes in Negative Lightning Leaders

et al. 2020

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“…Equation is a differential analog of the Rompe‐Weitzel formula for the conductivity of long spark channel [see Dulzon et al , ; Rompe and Weizel , ]. A similar approach was recently used by Iudin and Davydenko [], Davydenko and Iudin [] to describe the preliminary stage of compact intracloud discharges [e.g., Nag and Rakov , , ]. In contrast to the present model, they considered the development of streamer‐type discharges, which are characterized by relatively small currents, lower initial conductance of the channel, and smaller spatial extent.…”

Section: Model Descriptionmentioning

confidence: 99%

Advanced numerical model of lightning development: Application to studying the role of LPCR in determining lightning type

et al. 2017

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An advanced 3‐D numerical model of lightning development is presented. The key features of the model include the probabilistic branching, bidirectional propagation, nonzero internal electric field, simultaneous growth of multiple branches, physical timing, channel decay, and, for the first time, probabilistic propagation field threshold. The new model can be used for computing electrical parameters of individual branches, including conductivity, current, and longitudinal electric field, each as a function of time, in different parts of the discharge tree. For illustrative purposes, the model was applied to studying the occurrence of lightning flashes of different type depending on the cloud charge structure, with emphasis on the lower positive charge region (LPCR). We demonstrated with the new model that the presence of relatively large (excessive) LPCR can prevent the occurrence of negative CG flashes by “blocking” the progression of descending negative leader from reaching ground. The blocking effect of excessive LPCR was found to occur when the vertical component of electric field near the cloud bottom was negative (downward directed). Further, we showed that significant reduction or absence of LPCR can eliminate the possibility of negative CG flashes and lead to normal‐polarity IC flashes instead. The model predicts the polarity‐asymmetry, which suggests that the amount of collected charge depends not only on the number of branches but also on the dynamics of their conductivity (lifetime) and the local cloud charge density.

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“…There is, however, a lack of studies to understand the physical mechanism that enables CIDs to produce strong HF/VHF radiation, except the work by Iudin and Davydenko (2015) and Davydenko and Iudin (2016). Based on fractal modeling results, they suggested that CIDs are produced as a two-step process.…”

Section: Introductionmentioning

confidence: 99%

Understanding the Radio Spectrum of Thunderstorm Narrow Bipolar Events

et al. 2019

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This paper reports a study to understand the radio spectrum of thunderstorm narrow bipolar events (NBEs) or compact intracloud discharges, which are powerful sources of high-frequency (HF) and very high frequency (VHF) electromagnetic radiation. The radio spectra from 10 kHz to about 100 MHz are obtained for three NBEs, including one caused by fast positive breakdown and two by fast negative breakdown. The results indicate that the two polarities of fast breakdown have similar spectra, with a relatively flat spectrum in the HF and VHF band. The ratio of energy spectral densities in the very low frequency and HF bands is (0.9-5) × 10 5 . We develop a statistical modeling approach to investigate if a system of streamers can explain the main features of fast breakdown. Assuming that the current moment peak and charge moment change of individual streamers vary in the ranges of 5-10 A-m and 5-20 μC-m, respectively, the modeling results indicate that a system of 10 7 -10 8 streamers can reproduce the current moment, charge transfer, and radio spectrum of fast breakdown. The rapid current variation on a time scale of nanoseconds required for fast breakdown to produce strong HF/VHF emissions is provided by exponentially accelerating and expanding streamers. Our study therefore supports the hypothesis that fast breakdown is a system of streamers. Finally, suggestions are given regarding future streamer simulations and NBE measurements in order to further develop our understanding of NBEs and lightning initiation.

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Fractal Model of a Compact Intracloud Discharge. I. Features of the Structure and Evolution

Cited by 15 publications

References 52 publications

Numerical Simulation of Stepping and Branching Processes in Negative Lightning Leaders

Numerical Simulation of Stepping and Branching Processes in Negative Lightning Leaders

Advanced numerical model of lightning development: Application to studying the role of LPCR in determining lightning type

Understanding the Radio Spectrum of Thunderstorm Narrow Bipolar Events

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