HF radiation emitted by chaotic leader processes

Mäkelä, Jarmo; Edirisinghe, Mahesh; Fernando, Mahendra; Montaño, Raúl; Cooray, Vernon

doi:10.1016/j.jastp.2007.01.003

Cited by 23 publications

(20 citation statements)

References 19 publications

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“…The available evidence suggests that these pulses are associated with cloud processes, and a reasonable case can be made for there being a recoil streamer similar to that proposed for K changes but of much shorter duration [5]. As reported in [13], using measurements of HF at 10 MHz, shown that the "chaotic leaders" associated with subsequent return are a strong source of HF radiation.…”

Section: Introductionsupporting

confidence: 53%

“…A few studies have been carried out to understand the characteristics of lightning HF radiation [1,[3][4][5][6][7][8][9][10][11][12][13][14]. Two methods have traditionally been used to measure HF spectrum.…”

Section: Introductionmentioning

confidence: 99%

“…The problem occurs because of the inherent conflict between the requirement that the signal measured be truly representative of the power radiated at the frequency under investigation (a narrow bandwidth requirement) and the time resolution needed to distinguish between events in the flash (a large bandwidth requirement) [3]. A narrowband RLC tuned receiver was used successfully as a HF measuring system by [7] followed by [11][12][13][14]. For this study we have used narrowband RLC tuned receiver system, similar to [7] to detect HF radiation simultaneously with broadband electric field signal.…”

Section: Introductionmentioning

confidence: 99%

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Fine Structure Signatures in Ground Flashes as a Source for HF Radiation

Edirisinghe

Cooray

2013

ILCPA

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Lighting radiation fields below 10 MHz are of considerable interest since these frequencies correspond to the natural resonance of structures with dimensions of a few meters to tens of meters. In this paper we present the fine structure signatures of sub-microsecond range pulses appeared at the leader phase and after the return stroke in negative ground flashes which act as a source for HF radiations at 10 MHz, 5 MHz and 3 MHz observed in Sri Lanka, in the tropics. Of the total submicrosecond range pulses analyzed, 298 were due to positive field changes and 228 were due to negative field changes. The average rise time of those pulses for both polarities is 127 ns and it was found to be varying from 110-160 ns. The peak amplitude is in the range of 0.65-2.19 V/m. For the total 526 pulses analyzed for this study, the FWHM was between 190-310 ns with an arithmetic mean of 238 ns. Signatures of these pulses are similar to the leader like electric field pulses which acted as a strong source for HF radiations at 10 MHz, 5 MHz and 3 MHz. The initiation process of pulses reported in this study could be similar to the initiation process of leader like pulses.

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Section: Introductionsupporting

confidence: 53%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fine Structure Signatures in Ground Flashes as a Source for HF Radiation

Edirisinghe

Cooray

2013

ILCPA

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“…The HF radiation associated with CPTs was previously reported by Gomes et al [6] and Mäkela et al [11], but as far as we know there were no reports on measured HF radiation associated with RPTs. Figure 1a-d, Figures 2e and 3c show several examples of HF radiation associated with the CPT and the RPT.…”

Section: Hf Radiation (3 Mhz)mentioning

confidence: 65%

On the Possible Origin of Chaotic Pulse Trains in Lightning Flashes

et al. 2017

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Abstract:In this study, electromagnetic field radiation bursts known as chaotic pulse trains (CPTs) and regular pulse trains (RPTs) generated by lightning flashes were analyzed. Through a numerical analysis it was found that a typical CPT could be generated by superimposing several RPTs onto each other. It is suggested that the chaotic pulse trains are created by a superposition of several regular pulse trains. Since regular pulse trains are probably created by dart or dart-stepped leaders or K-changes inside the cloud, chaotic pulse trains are caused by the superposition of electric fields caused by more than one of these leaders or K-changes propagating simultaneously. The hypothesis is supported by the fact that one can find regular pulse trains either in the beginning, middle or later stages of chaotic pulse trains.

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“…The causative storms were 10 to 150 km distant. It was reported that CPTs immediately preceding subsequent return strokes had pulse widths generally in the range from 2 to 4 μ s (measured as short as 400 ns), interpulse intervals from 2 to 20 μ s, and mode value duration of 400 to 500 μ s. Mäkelä et al [2007] also performed an analysis of “chaotic” leaders in Sri Lanka using both a wideband (upper frequency limit of about 12 MHz) flat‐plate electric field antenna and a vertical antenna tuned to a resonant frequency of 10.44 MHz with a bandwidth of 2.02 MHz. They analyzed 34 lightning flashes containing 74 subsequent return strokes, more than 30% of which appeared to be preceded by “chaotic” leaders.…”

Section: Introductionmentioning

confidence: 99%

“Chaotic” dart leaders in triggered lightning: Electric fields, X‐rays, and source locations

et al. 2012

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.[1] We present the first published observations of "chaotic" dart leaders in triggered-lightning discharges. We examine four leaders that exhibited "chaotic" electric field derivative (dE/dt) signatures in their final 10 to 12 ms. The dE/dt signatures were characterized by bursts exhibiting widths of the order of hundreds of nanoseconds on which were superimposed irregular pulses with widths of the order of tens of nanoseconds. These unique signatures were dissimilar from the dE/dt waveforms observed from dart or dart-stepped leaders in triggered lightning. Three-dimensional locations for dE/dt pulses that radiated from the bottom 200 m of the leader channels were determined, as were emission times. Vertical leader speeds for the four "chaotic" dart leaders were estimated to range from 2.0 to 4.3 Â 10 7 m/s. A relatively continuous flux of energetic radiation (X-rays and gamma rays) was observed during the final 10-13 ms of each "chaotic" dart leader. Some individual photons had energies more than 1 MeV. High-speed video images of three "chaotic" dart leaders were obtained at a frame rate of 300 kilo-frames per second (exposure time of 3.33 ms). One image, in the frame immediately prior to the return stroke, shows an upward positive leader 11.5 m in length propagating from the launch facility and a downward negative leader above with a streamer zone length of about 25 m. Channel base currents preceding the four "chaotic" dart leaders were of unusually long duration and large charge transfer, and return strokes following them had larger than usual peak currents.

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HF radiation emitted by chaotic leader processes

Cited by 23 publications

References 19 publications

Fine Structure Signatures in Ground Flashes as a Source for HF Radiation

Fine Structure Signatures in Ground Flashes as a Source for HF Radiation

On the Possible Origin of Chaotic Pulse Trains in Lightning Flashes

“Chaotic” dart leaders in triggered lightning: Electric fields, X‐rays, and source locations

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