Modeling initial breakdown pulses of CG lightning flashes

Abstract

Electric field change waveforms of initial breakdown pulses (IBPs) in cloud-to-ground (CG) lightning flashes were recorded at ten sites at Kennedy Space center, Florida, in 2011. Six "classic" IBPs were modeled using three modified transmission line (MTL) models called MTLL, MTLE, and MTLK. The locations of the six IBPs were obtained using a time-of-arrival method and used as inputs for the models; the recorded IBP waveforms from six to eight sites were used as model constraints. All three models were able to reasonably fit the measured IBP waveforms; the best fit was most often given by the MTLE model. For each individual IBP, there was good agreement between the three models on several physical parameters of the IBPs: current risetime, current falltime, current shape factor, current propagation speed, and the total charge moment change. For the six IBPs modeled, the ranges, mean values, and standard deviations of these quantities are as follows: current risetime

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

“…Figure shows a more detailed view on the leader's current distribution. Figures a–h show snapshots of the simulated I ( z , t ) (solid line) and comparison to TL model results by Karunarathne et al [] (dashed line). Figures i–j present 2‐D distributions of I ( z , t ) comparing our model results (i) to the previous work (j).…”

“…The input parameters used are summarized in the first line of Table . The simulated multistation electric field waveforms are shown in Figure in the same format as presented by Karunarathne et al [, Figure 4]. The full dynamics of charges (a), potential (b), current (c), and line conductivity (d) are shown in Figure .…”

“…Simulated electric field IBP waveform as observed by four sensors at different ranges D , as reported by Karunarathne et al [, Figure 4]. Time is measured from the arrival of the first peak in the closest sensor.…”

“…There are two classes of theoretical models for the source of electrical current, I ( z , t ), that generates IBP and NBE pulses. The first one is referred to as transmission line model and it was applied to make inferences about the sources of both IBP and NBE signatures [e.g., Shao and Heavner , ; Watson and Marshall , ; Nag and Rakov , ; Karunarathne et al , ]. The second one is based on the assumption that relativistic runaway electron avalanches seeded by cosmic ray air showers are the source of NBEs [e.g., Gurevich et al , , ; Gurevich and Zybin , ; Tierney et al , ; Arabshahi et al , ].…”

Initial breakdown and fast leaders in lightning discharges producing long‐lasting disturbances of the lower ionosphere

“…Among all lightning flashes, IB pulses were rarely observed in VLF (with >8 dB SNR) at distances greater than a few hundred kilometers, as will be discussed in the next section. Based on this criterion, we have classified the IB radiation reported in this paper (observed at distances greater than a few hundred kilometers) as “intense.” Recent experimental and modeling studies indicate that peak currents producing IB pulses may be as large as several tens of kiloamps [ Karunarathne et al , ; da Silva and Pasko , ; Kolmašová et al , ], flowing over channels with lengths on the order of a few hundred meters to a kilometer [ Stolzenburg et al , , ; Karunarathne et al , ; da Silva and Pasko , ; Nag and Rakov , ]. Such large currents have been demonstrated to produce initial breakdown observable at a distance of 600 km [ Kolmašová et al , , ].…”