uu.seUppsala University Publications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Characteristics of narrow bipolar pulses observed in Malaysia
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.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Show others and affiliations
2010 (English)In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, no 5-6, 534-540 p.Article in journal (Refereed) Published
Abstract [en]

Narrow bipolar pulses (NBPs) are considered as isolated intracloud events with higher peak amplitude and strong high frequency emission compared to the first return strokes and other intracloud discharges. From 182 NBPs recorded in Malaysia in the tropic, 75 were narrow negative bipolar pulses (NNBPs) while 107 were narrow positive bipolar pulses (NPBPs). The mean duration of NNBPs was 24.6 +/- 17.1 mu s, while 30.2 +/- 12.3 mu s was observed for NPBPs. The mean full-width at half-maximum (FVVHM) was 2.2 +/- 0.7 and 2.4 +/- 1.4 mu s for NNBPs and NPBPs, respectively. The mean peak amplitude of NPBPs normalized to 100 km was 22.7 V/m, a factor of 1.3 higher than that of NNBPs which is 17.6 V/m. In contrast to the previous studies, it was observed that the electric field change was characterized by a bipolar pulse with a significant amount of fine structures separated by a few tens of nanoseconds intervals, embedded on it. (C) 2010 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
2010. Vol. 72, no 5-6, 534-540 p.
Keyword [en]
Narrow bipolar pulses, Lightning, Cloud discharges, Electric field
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-137067DOI: 10.1016/j.jastp.2010.02.006ISI: 000276428600020OAI: oai:DiVA.org:uu-137067DiVA: diva2:378339
Available from: 2010-12-15 Created: 2010-12-15 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Broadband and HF Radiation from Cloud Flashes and Narrow Bipolar Pulses
Open this publication in new window or tab >>Broadband and HF Radiation from Cloud Flashes and Narrow Bipolar Pulses
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Remote measurement of electric field generated by lightning has played a major role in understanding the lightning phenomenon. Even though other measurements such as photographic and channel base current have contributed to this research field, due to practical reasons remote measurements of electric field is considered as the most useful tool in lightning research.

This thesis discusses the remotely measured radiation field component of electric field generated by cloud flashes (ICs) and narrow bipolar pulses (NBPs). The associated HF radiation of these events at 3 MHz and 30 MHz are also discussed. To understand the initiation process of these discharges, a comparative study of the initial pulse of cloud flashes against the initial pulse of cloud to ground flashes was conducted. The result suggests that both discharges might have been initiated by similar physical processes inside the thunderclouds. Comparing the features of initial pulse of cloud and ground flashes with that of pulses that appeared in the later stages of cloud flashes suggests that the initiation process involved in both flashes are not very much different from the initiation of cloud flashes at the later stage. The average spectral amplitudes of electric field of full duration cloud flashes (180 ms) showed -1 frequency dependence within the interval of 10 kHz to approximately 10 MHz. This is in contrast to the standard -2 decrement (or even steeper ) at high frequency region for other lightning processes such as return strokes. It was suggested that small pulses which repeatedly appeared at the later stage of cloud flashes might have contributed to enhance the spectral amplitude at higher frequencies.

Electric fields generated by Narrow Bipolar Pulses (NBPs), which are considered as one of the strongest sources of HF radiation, were measured in the tropics of Malaysia and Sri Lanka.  Their features were also studied and show a good agreement with previously published observations of NBPs from other geographical regions. Thorough analyses and observations of these pulses found previously unreported sharp, fine peaks embedded in the rising and decaying edge of the electric field change of NBPs. Therefore it was suggested that these fine peaks are mostly responsible for the intense HF radiation at 30 MHz.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 64 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 822
Keyword
Lightning, Cloud Flashes, Narrow Bipolar Pulses, HF radiation
National Category
Other Physics Topics
Research subject
Engineering Science with specialization in Atmospheric Discharges
Identifiers
urn:nbn:se:uu:diva-150956 (URN)978-91-554-8067-7 (ISBN)
Public defence
2011-05-25, Å2001, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 14:15 (English)
Opponent
Supervisors
Available from: 2011-05-03 Created: 2011-04-08 Last updated: 2011-07-01Bibliographically approved
2. Characterizations of ground flashes from tropic to northern region
Open this publication in new window or tab >>Characterizations of ground flashes from tropic to northern region
2014 (English)Doctoral thesis, comprehensive summary (Other academic) [Artistic work]
Abstract [en]

This thesis portrays new information concerning the cloud-to-ground (CG) lightning flashes or ground flashes produced by thunderclouds. It emphasizes the importance of characterizing lightning studies as the relationship between lightning mechanisms, and of incorporating the influence of geographical location, latitude and storm type. Sweden, Malaysia and USA were chosen as the main locations for field experiments in 2009 to 2011 to gather a significant number of negative and positive CG flashes. This work provided data on a total of 1792 CG lightning flashes (1685 negative and 107 positive ones) from a total of 53 thunderstorms by monitoring both the slow and the fast electric field and the narrowband radiation field at 3 and 30 MHz signals simultaneously. This thesis is comprised of: (i) the relationship of the Low Positive Charge Region (LPCR) and Preliminary Breakdown Pulse (PBP) trains to the occurrence of negative CG, (ii) slow field changes generated by preliminary breakdown processes in positive and negative ground flashes, and (iii) the occurrence of positive and negative ground flashes. It was revealed that the PBP train appeared have a higher strength in the in Sweden. The strength of the PBP train was caused by the LPCR; in contrast,  weak PBP trains were characteristic in tropical countries constituting insignificant LPCR and needing little energy to break the “blocking” agent to allow the flash to propagate downward to the ground. The second contribution concerns the characteristics of the PBP train mentioned; this includes novel information for Malaysia. Further, it is stated that there are some different characteristics in the PBP trains in Johor, Malaysia and Florida, USA. The studies of slow field changes generated by preliminary breakdown processes clarifies unclear features concerning the starting position of slow field changes generated by preliminary breakdown processes in positive and negative ground flashes. It was found that the slow field changes did not occur before the initial process of the commencement of preliminary breakdown. Single-station electric field measurements incorporating narrowband radiation field measurement and high resolution transient recording (12 bits) with an accuracy of several nanoseconds, allows one to distinguish between the intracloud activities and the preceding processes of ground flashes. The results for the interstroke intervals, amplitude distribution of subsequent return-stroke (SRS) and the number of strokes per flash in the tropics, subtropics and northern regions were similar. Finally, a significant number of positive return-stroke (RS) electric fields provided statistically significant information on the characteristics of these strokes.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. 78 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1145
Keyword
Positive/negative cloud-to-ground lightning flashes, Initiation position, slow field changes, close ground flashes, preliminary breakdown process
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Atmospheric Discharges
Identifiers
urn:nbn:se:uu:diva-222838 (URN)978-91-554-8946-5 (ISBN)
Public defence
2014-06-03, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Funder
Swedish Research Council, 621-2006-4299
Available from: 2014-05-12 Created: 2014-04-15 Last updated: 2016-04-29

Open Access in DiVA

No full text

Other links

Publisher's full text

Authority records BETA

Baharudin, Zikri A.Cooray, Vernon

Search in DiVA

By author/editor
Baharudin, Zikri A.Cooray, Vernon
By organisation
Electricity
In the same journal
Journal of Atmospheric and Solar-Terrestrial Physics
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 598 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf