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Electric field changes generated by preliminary breakdown pulse for positive lightning ground flashes in Sweden
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. (Division of Electricity)
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. (Division of Electricity)
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. (Division of Electricity)
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper. (Division of Electricity)
Visa övriga samt affilieringar
(Engelska)Manuskript (preprint) (Övrigt vetenskapligt) [Forskning på konstnärlig grund]
Abstract [en]

This is the new study of the electric field changes generated by the preliminary breakdown for positive cloud-to-ground flashes which concerning on the association of slow field changes in preliminary breakdown process. In this study, a 107 positive cloud-to-ground lightning flashes recorded from the total of 14 thunderstorms generated by the whole flash were examined. The electric fields were measured with nanosecond resolution by using the slow electric field, fast electric field and narrowband radiation field at 3 and 30 MHz signals simultaneously. Our result shows that there is a pre-starting time, i.e. the duration between the first preliminary breakdown pulse and slow field changes starting point, which is found to be after the first preliminary breakdown pulse. The pre-starting time has the arithmetic mean – 3.0 ms and geometric mean – 1.8 ms, ranging from 0.3 to 21.7 ms. This study is consistent with the latest finding for the slow field changes in negative ground flashes where the slow field changes never start before the preliminary breakdown process.

Nyckelord [en]
Positive cloud-to-ground lightning flashes, Initiation position, slow field changes, close ground flashes, preliminary breakdown process
Nationell ämneskategori
Annan elektroteknik och elektronik
Forskningsämne
Teknisk fysik med inriktning mot atmosfäriska urladdningar
Identifikatorer
URN: urn:nbn:se:uu:diva-222826OAI: oai:DiVA.org:uu-222826DiVA, id: diva2:712381
Forskningsfinansiär
Vetenskapsrådet, 621-2006-4299Stiftelsen för strategisk forskning (SSF), IG2004–2031Tillgänglig från: 2014-04-15 Skapad: 2014-04-14 Senast uppdaterad: 2017-11-09Bibliografiskt granskad
Ingår i avhandling
1. Characterizations of ground flashes from tropic to northern region
Öppna denna publikation i ny flik eller fönster >>Characterizations of ground flashes from tropic to northern region
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt) [Forskning på konstnärlig grund]
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.

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2014. s. 78
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1145
Nyckelord
Positive/negative cloud-to-ground lightning flashes, Initiation position, slow field changes, close ground flashes, preliminary breakdown process
Nationell ämneskategori
Annan elektroteknik och elektronik
Forskningsämne
Teknisk fysik med inriktning mot atmosfäriska urladdningar
Identifikatorer
urn:nbn:se:uu:diva-222838 (URN)978-91-554-8946-5 (ISBN)
Disputation
2014-06-03, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:00 (Engelska)
Opponent
Handledare
Forskningsfinansiär
Vetenskapsrådet, 621-2006-4299
Tillgänglig från: 2014-05-12 Skapad: 2014-04-15 Senast uppdaterad: 2018-05-28

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Baharudin, Zikri AbadiCooray, VernonRahman, MahbuburHettiarachchi, Pasan
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Institutionen för teknikvetenskaper
Annan elektroteknik och elektronik

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