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Wavelet Profile of Initial Breakdown Process Accompanied by Narrow Bipolar Pulses
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2014 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824Article in journal (Refereed) Submitted
Place, publisher, year, edition, pages
2014.
Keyword [en]
Initial breakdown process; Narrow bipolar pulse; Wavelet.
National Category
Meteorology and Atmospheric Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Atmospheric Discharges
Identifiers
URN: urn:nbn:se:uu:diva-233650OAI: oai:DiVA.org:uu-233650DiVA: diva2:753414
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05
In thesis
1. Temporal and Wavelet Characteristics of Initial Breakdown and Narrow Bipolar Pulses of Lightning Flashes
Open this publication in new window or tab >>Temporal and Wavelet Characteristics of Initial Breakdown and Narrow Bipolar Pulses of Lightning Flashes
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Temporal and wavelet characteristics of initial breakdown pulses are meticulously studied especially during the earliest moment of lightning events. Any possible features during the earliest moment that may exist which lead to either negative cloud-to-ground (CG), positive cloud-to-ground, cloud or isolated breakdown flashes in Sweden are investigated. Moreover, the occurrence of narrow bipolar pulses (NBPs) as part of a CG event that has been recorded from tropical thunderstorms are also included in the investigation. Electric field signatures selected from a collection of waveforms recorded using fast electric field broadband antenna system installed in Uppsala, Sweden and Skudai, South Malaysia are then carefully analyzed in order to observe any similarities or/and differences of their features.

Temporal analysis reveals that there are significant distinctions within the first 1 ms among different types of lightning flashes. It is found that a negative CG flash tends to radiate pulses more frequently than other flashes and a cloud flash tends to radiate shorter pulses than other flashes but less frequently when compared to negative CG and isolated breakdown flashes. Perhaps, the ionization process during the earliest moment of negative CG flashes is more rapid than other discharges. Using a wavelet transformation, it can be suggested that the first electric field pulse of both negative CG and cloud flashes experiences a more rapid and extensive ionization process compared to positive CG and isolated breakdown flashes.

Further temporal analysis on NBPs found to occur as part of CG flashes show the disparity of the normalized electric field amplitude between the NBPs prior to and after the first return stroke. This indicates that the NBPs intensities were influenced by the return stroke events and they occurred in the same thundercloud. The similarity between the temporal characteristics of NBPs as part of CG flashes and isolated NBPs suggests that their breakdown mechanisms might be similar.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 51 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1190
Keyword
Initial breakdown; Lightning flash; Narrow bipolar pulse; Temporal-Wavelet characterization
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Meteorology and Atmospheric Sciences
Research subject
Engineering Science with specialization in Atmospheric Discharges
Identifiers
urn:nbn:se:uu:diva-233671 (URN)978-91-554-9070-6 (ISBN)
Public defence
2014-12-01, Polhemsalen, Ångströmslaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:00 (English)
Opponent
Supervisors
Available from: 2014-11-07 Created: 2014-10-08 Last updated: 2015-01-23

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Mohd Esa, Mona RizaAhmad, Mohd RiduanCooray, Vernon

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