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Characterizations of ground flashes from tropic to northern region
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Elektricitetslära.
2014 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig) [Kunstnerisk arbeiden]
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.

sted, utgiver, år, opplag, sider
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
Emneord [en]
Positive/negative cloud-to-ground lightning flashes, Initiation position, slow field changes, close ground flashes, preliminary breakdown process
HSV kategori
Forskningsprogram
Teknisk fysik med inriktning mot atmosfäriska urladdningar
Identifikatorer
URN: urn:nbn:se:uu:diva-222838ISBN: 978-91-554-8946-5 (tryckt)OAI: oai:DiVA.org:uu-222838DiVA, id: diva2:712383
Disputas
2014-06-03, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:00 (engelsk)
Opponent
Veileder
Forskningsfinansiär
Swedish Research Council, 621-2006-4299Tilgjengelig fra: 2014-05-12 Laget: 2014-04-15 Sist oppdatert: 2018-05-28
Delarbeid
1. Comparative study on preliminary breakdown pulse trains observed in Johor, Malaysia and Florida, USA
Åpne denne publikasjonen i ny fane eller vindu >>Comparative study on preliminary breakdown pulse trains observed in Johor, Malaysia and Florida, USA
Vise andre…
2012 (engelsk)Inngår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895, Vol. 117, s. 111-121Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this paper, the preliminary breakdown (PB) pulse train preceding the negative first return stroke (RS) is recorded using a broad band antenna system. These analyses were carried out in Johor Bahru, Malaysia and Florida, United States. This is a novel initiative at examining and identifying the characteristics of the PB pulse trains in the negative cloud-to-ground flashes observed in Malaysia. The arithmetic mean of the total pulse train duration is 12.3 ms and the weighted arithmetic mean of the pulse durations and interpulse intervals are 11 mu s and 152 mu s, respectively. The arithmetic mean ratio between the maximum peak amplitude of the PB pulse and the peak RS electric field was 27.8%, and the corresponding value in Florida was 29.4%. The arithmetic mean of the time duration between the most active part of the pulse train, and the RS was 57.6 ms in Malaysia and 22 ms in Florida. A qualitative comparison of our results with those obtained earlier in Sri Lanka. Sweden and Finland supports the hypothesis that the PBP/RS ratio is higher in the northern regions compared to the tropical regions. (C) 2012 Elsevier B.V. All rights reserved.

Emneord
Preliminary breakdown pulses, PB/RS ratio, PB-RS separation
HSV kategori
Forskningsprogram
Teknisk fysik med inriktning mot elektricitetslära
Identifikatorer
urn:nbn:se:uu:diva-184450 (URN)10.1016/j.atmosres.2012.01.012 (DOI)000309300100015 ()
Tilgjengelig fra: 2012-11-09 Laget: 2012-11-07 Sist oppdatert: 2017-12-07bibliografisk kontrollert
2. Electric field changes generated by the preliminary breakdown for the negative cloud-to-ground lightning flashes in Malaysia and Sweden
Åpne denne publikasjonen i ny fane eller vindu >>Electric field changes generated by the preliminary breakdown for the negative cloud-to-ground lightning flashes in Malaysia and Sweden
Vise andre…
2012 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 84-85, s. 15-24Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We present the study of the electric field changes generated by the preliminary breakdown for negative cloud-to-ground lightning flashes in Malaysia and Sweden concerning the association of slow field changes associated in preliminary breakdown process. We examined the total of 1685 negative cloud-to-ground lightning flashes from the total of 39 thunderstorms by recording the slow electric field, fast electric field and narrowband radiation field at 3 and 30 MHz signals simultaneously. Our results show 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 and geometric mean range from 1.4-6.47 and 1-3.36 ms, respectively. The mean values of pre-starting time in Malaysia are greater than the values observed in Sweden by more than a factor of 3. From the two data sets it shows that the slow field changes never start before the preliminary breakdown. Furthermore, the use of single-station electric fields measurement with high resolutions of 12 bits transient recorder with several nanosecond accuracy allow one to distinguish the slow field changes generated by preliminary breakdown, which preceded the negative first return stroke, between tens to hundreds of milliseconds of pre-return stroke duration.

Emneord
Initiation position, Slow field changes, Close ground flashes, Preliminary breakdown process
HSV kategori
Forskningsprogram
Teknisk fysik med inriktning mot atmosfäriska urladdningar
Identifikatorer
urn:nbn:se:uu:diva-182547 (URN)10.1016/j.jastp.2012.04.009 (DOI)000308512100003 ()
Tilgjengelig fra: 2012-10-11 Laget: 2012-10-11 Sist oppdatert: 2017-12-07
3. Electric field changes generated by preliminary breakdown pulse for positive lightning ground flashes in Sweden
Åpne denne publikasjonen i ny fane eller vindu >>Electric field changes generated by preliminary breakdown pulse for positive lightning ground flashes in Sweden
Vise andre…
(engelsk)Manuskript (preprint) (Annet vitenskapelig) [Kunstnerisk arbeiden]
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.

Emneord
Positive cloud-to-ground lightning flashes, Initiation position, slow field changes, close ground flashes, preliminary breakdown process
HSV kategori
Forskningsprogram
Teknisk fysik med inriktning mot atmosfäriska urladdningar
Identifikatorer
urn:nbn:se:uu:diva-222826 (URN)
Forskningsfinansiär
Swedish Research Council, 621-2006-4299Swedish Foundation for Strategic Research , IG2004–2031
Tilgjengelig fra: 2014-04-15 Laget: 2014-04-14 Sist oppdatert: 2017-11-09bibliografisk kontrollert
4. Negative cloud-to-ground lightning flashes in Malaysia
Åpne denne publikasjonen i ny fane eller vindu >>Negative cloud-to-ground lightning flashes in Malaysia
Vise andre…
2014 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 108, s. 61-67Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The characteristics of the negative cloud-to-ground lightning flashes in Malaysia are studied by analyzing the electric fields generated by the whole flash in nanosecond resolution. A total of 405 strokes obtained from 100 successive negative cloud-to-ground lightning flashes were analyzed, which were recorded from seven convective thunderstorms during the southwest monsoon period, i.e. from April to June 2009. It was found that the total number of interstroke intervals has an arithmetic mean value of 86 ms, a geometric mean value of 67 ms and does not depend on the return stroke order. Of the 100 negative ground flashes, 38 flashes (38%) have at least one subsequent return-stroke (SRS) whose electric field peak was greater than that of the first return-stroke (RS). Furthermore, 58 (19%) out of 305 SRS have electric field peak larger than those of the first RS. The arithmetic and geometric mean ratio between the peak electric field of the SRS and the peak electric field of the first RS are 0.7 and 0.6, respectively. The percentage of single-stroke flashes was 16% while the mean number of strokes per flash and maximum number of stroke per flash were 4 and 14, respectively.

Emneord
Negative cloud-to-ground lightning flashes, Number of strokes per flash and interstroke interval
HSV kategori
Forskningsprogram
Teknisk fysik med inriktning mot elektricitetslära
Identifikatorer
urn:nbn:se:uu:diva-221965 (URN)10.1016/j.jastp.2013.12.001 (DOI)000331684900007 ()
Tilgjengelig fra: 2014-04-10 Laget: 2014-04-07 Sist oppdatert: 2017-12-05bibliografisk kontrollert
5. On the characteristics of positive lightning ground flashes in Sweden
Åpne denne publikasjonen i ny fane eller vindu >>On the characteristics of positive lightning ground flashes in Sweden
Vise andre…
2016 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 138, s. 106-111Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this study the stroke characteristics of positive cloud-to-ground flashes in Sweden were obtained from the electric field records measured from 14 thunderstorms. The electric fields were measured with nanosecond resolution. Together with the fast and the slow electric field records, the narrowband radiation field at 3 and 30 MHz signals were also measured simultaneously. Out of a total of 107 flashes, 30 flashes had two strokes, 7 had three strokes and 3 flashes had four strokes. The arithmetic and geometric means of the interstroke intervals were found to be 116 and 70 ms, respectively. The arithmetic and geometric mean ratio between the peak electric field of the Subsequent Return Stroke (SRS) and the first Return Stroke (RS) were 0.48 and 0.36, respectively. Of the 40 positive multiple-stroke ground flashes, 5% have at least one SRS with field peak higher than the first RS. The percentage of SRS with field peaks greater than the first RS was 6%. In our best of our knowledge, this is the first time a large sample of positive return strokes in Sweden was analysed. It was found to be statistically more significant than the previous studies.

Emneord
Lightning flashes, Positive ground flashes, Positive return strokes, Electromagnetic fields
HSV kategori
Forskningsprogram
Teknisk fysik med inriktning mot atmosfäriska urladdningar
Identifikatorer
urn:nbn:se:uu:diva-274994 (URN)10.1016/j.jastp.2015.12.014 (DOI)000370769900011 ()
Forskningsfinansiär
Swedish Research Council, 621-2006-4299
Tilgjengelig fra: 2016-01-27 Laget: 2016-01-27 Sist oppdatert: 2017-11-30bibliografisk kontrollert
6. Comparative Study on Preliminary Breakdown Pulse Trains Observed in Malaysia and Florida
Åpne denne publikasjonen i ny fane eller vindu >>Comparative Study on Preliminary Breakdown Pulse Trains Observed in Malaysia and Florida
Vise andre…
2010 (engelsk)Konferansepaper, Publicerat paper (Fagfellevurdert)
sted, utgiver, år, opplag, sider
Cagliary, Italy: , 2010
HSV kategori
Forskningsprogram
Teknisk fysik med inriktning mot atmosfäriska urladdningar
Identifikatorer
urn:nbn:se:uu:diva-140393 (URN)
Konferanse
30TH International Conference on Lightning Protection, ICLP
Tilgjengelig fra: 2011-01-05 Laget: 2011-01-05 Sist oppdatert: 2018-05-28
7. The first electric field pulse of cloud and cloud-to-ground lightning discharges
Åpne denne publikasjonen i ny fane eller vindu >>The first electric field pulse of cloud and cloud-to-ground lightning discharges
Vise andre…
2010 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, nr 2-3, s. 143-150Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this study, the first electric field pulse of cloud and cloud-to-ground discharges were analyzed and compared with other pulses of cloud discharges. Thirty eight cloud discharges and 101 cloud-to-ground discharges have been studied in this analysis. Pulses in cloud discharges were classified as [`]small', [`]medium' and [`]large', depending upon the value of their relative amplitude with respect to that of the average amplitude of the five largest pulses in the flash. We found that parameters, such as pulse duration, rise time, zero crossing time and full-width at half-maximum (FWHMs) of the first pulse of cloud and cloud-to-ground discharges are similar to small pulses that appear in the later stage of cloud discharges. Hence, we suggest that the mechanism of the first pulse of cloud and cloud-to-ground discharges and the mechanism of pulses at the later stage of cloud discharges could be the same.

Emneord
Cloud discharges, Electromagnetic field, Lightning, Electric field pulses
HSV kategori
Forskningsprogram
Teknisk fysik med inriktning mot atmosfäriska urladdningar
Identifikatorer
urn:nbn:se:uu:diva-140337 (URN)10.1016/j.jastp.2009.11.001 (DOI)
Tilgjengelig fra: 2011-01-05 Laget: 2011-01-05 Sist oppdatert: 2017-12-11
8. Radiation Field Spectra of Long-duration Cloud Flashes
Åpne denne publikasjonen i ny fane eller vindu >>Radiation Field Spectra of Long-duration Cloud Flashes
(engelsk)Inngår i: IEEE transactions on electromagnetic compatibility (Print), ISSN 0018-9375, E-ISSN 1558-187XArtikkel i tidsskrift (Fagfellevurdert) Submitted
Abstract [en]

The radiation electric fields produced by long-duration cloud flashes have been Fourier analyzed to determined the frequency spectrum in the range of 10 kHz to 10 MHz. The flashes were recorded within a distance of less than 20 km. The spectrum was normalized to 50 km distance and it shows a f-1 dependence within the entire frequency range.

Identifikatorer
urn:nbn:se:uu:diva-150952 (URN)
Tilgjengelig fra: 2011-04-08 Laget: 2011-04-08 Sist oppdatert: 2017-12-11
9. Characteristics of narrow bipolar pulses observed in Malaysia
Åpne denne publikasjonen i ny fane eller vindu >>Characteristics of narrow bipolar pulses observed in Malaysia
Vise andre…
2010 (engelsk)Inngår i: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 72, nr 5-6, s. 534-540Artikkel i tidsskrift (Fagfellevurdert) 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.

Emneord
Narrow bipolar pulses, Lightning, Cloud discharges, Electric field
HSV kategori
Identifikatorer
urn:nbn:se:uu:diva-137067 (URN)10.1016/j.jastp.2010.02.006 (DOI)000276428600020 ()
Tilgjengelig fra: 2010-12-15 Laget: 2010-12-15 Sist oppdatert: 2017-12-11bibliografisk kontrollert
10. Some features of electric field waveform of Narrow Bipolar Pulses
Åpne denne publikasjonen i ny fane eller vindu >>Some features of electric field waveform of Narrow Bipolar Pulses
(engelsk)Inngår i: Atmospheric research, ISSN 0169-8095, E-ISSN 1873-2895Artikkel i tidsskrift (Fagfellevurdert) Submitted
Abstract [en]

Narrow Bipolar Pulses (NBPs) are generated by intra-cloud discharge processes and they are of interest due to their strong broadband and high frequency (HF) emissions. In this study, we present some features of electric field waveform of NBPs which have not been reported in the literature.  The HF emission was observed to begin simultaneously with the onset of NBPs indicating no streamers or stepped-leader process was taking place before the initiation of NBPs. The electric field waveforms of NBPs were characterized by many fine peaks embedded intermittently on the rising and decaying edge of NBPs suggesting that some small scale electrical discharges were involved during the formation of NBPs.

 

Identifikatorer
urn:nbn:se:uu:diva-150953 (URN)
Tilgjengelig fra: 2011-04-08 Laget: 2011-04-08 Sist oppdatert: 2017-12-11

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