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| 2. |
- Cooray, Vernon, et al.
(författare)
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Lightning parameters of engineering interest
- 2009
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Ingår i: Lightning Protection. - London : The Institution of Engineering and Technology, London, UK. - 9780863417443
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Bokkapitel (populärvet., debatt m.m.)
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| 3. |
- Fernando, Mahendra, et al.
(författare)
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Lightning and trees
- 2009
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Ingår i: Lightning Protection. - London : The Institution of Engineering and Technology, London, UK. - 9780863417443
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Bokkapitel (populärvet., debatt m.m.)
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| 9. |
- Sharma, S. R., et al.
(författare)
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Isolated breakdown activity in Swedish lightning
- 2008
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 70:8-9, s. 1213-1221
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Tidskriftsartikel (refereegranskat)abstract
- The initial breakdown processes or preliminary breakdown (PB) processes are generally associated with either cloud or cloud-ground lightning flashes, and hence have been studied mainly in connection with those subsequent activities. However, it has been observed in the summer thunderstorms of Sweden that there are breakdown processes that may not culminate into any subsequent activity. As these processes do not lead to any subsequent activity, they have been termed as isolated breakdown activities. Such isolated breakdown activities involve microsecond-scale pulses with both initial polarities. Based on their polarities, breakdown processes are divided into two groups, the negative breakdown pulses that are similar to the breakdown pulses leading to negative return strokes in ground flashes and the positive breakdown pulses similar to the breakdown pulses generally leading to the cloud flashes. The occurrence of the two types of breakdown processes is found to vary from a thunderstorm day to the other. In the present study, the signatures of isolated breakdown activities have been analyzed and are compared with those leading to the subsequent activities observed during the same measurement campaign. The average duration of the isolated breakdown activity associated with the negative initial polarity pulses is found to be 0.98 ms with average number of pulses 8.5. Similarly, the average duration and number of pulses in the isolated breakdown process with positive initial polarity pulses are 6.9ms and 3.9, respectively.
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| 10. |
- Sharma, S. R., et al.
(författare)
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Narrow positive bipolar radiation from lightning observed in Sri Lanka
- 2008
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826. ; 70:10, s. 1251-1260
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Tidskriftsartikel (refereegranskat)abstract
- Narrow positive bipolar pulses (NPBPs), whose origin largely remains unknown as yet, have occasionally been noticed in Sri Lanka. These discharges are found to be opposite in polarity to that of negative return strokes, and are found to occur at the beginning and active stage of thunderstorm activities in Sri Lanka. They are emitted from the thunderstorms that produce other activities also and are relatively narrower, bipolar and isolated in nature. They are neither preceded by leader-type pulses nor succeeded by the subsequent activities and hence, could not be associated with any other known activity. Similar radiations have previously been identified and termed as NPBPs. Their features are indeed unique and different from the other known thunderstorm electrical processes. These events have been found to be accompanied by the HF radiations at 5 and 10 MHz, at the trailing part of the pulse. However, such narrow, bipolar and isolated events have not been observed in Sweden, during a lightning measurement campaign at Uppsala, in 2006. So, it is speculated that the meteorological conditions to be responsible for the thunderstorm activity to produce such pulses. Features of such pulses recorded on different thunderstorm days in 2005 and 2006 have been analyzed and presented in this study. The average rise time (10-90%) (Tr), of the pulses was found to be 2.6 [mu]s, the average zero crossing time (Tz) was found to be 5.85 [mu]s, the average duration of slow front (Ts) was found to be 1.86 [mu]s, and the average ratio of amplitude of overshoot to the corresponding peak amplitude (Os/Pa) of these pulses was found to be 0.39.
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