| 11. |
- Perera, Chandana, et al.
(författare)
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Continuing Currents and Luminosity of Cloud Flashes
- 2014
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Ingår i: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP). - : IEEE conference proceedings. - 9781479935444 ; , s. 1587-1593
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Konferensbidrag (refereegranskat)abstract
- In this study, continuing currents and luminosity of cloud flashes were investigated using time resolve photographic technique. In ground flashes, the flow of current after the end of the return stroke is called the continuing currents. Typical cloud flashes have two stages called early stage (or active stage) and final or late stage. The continuing current and luminosities reported in this paper are observed in late stage of the cloud flashes. In ground flashes the shortest reported duration of continuing current is longer than the 3 ms. For the first time in literature the continuing currents in cloud flashes were studied. No major difference between the time duration of continuing currents of ground flashes and long current variation of cloud flashes were observed.
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| 12. |
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| 13. |
- Sharma, S R, et al.
(författare)
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Temporal features of different lightning events revealed from wavelet transform
- 2011
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 73:4, s. 507-515
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Tidskriftsartikel (refereegranskat)abstract
- Various lightning events are analysed using wavelet transform. The events include PB pulses, stepped leaders, first return strokes, subsequent strokes associated with negative ground flashes, positive return strokes and narrow bipolar pulses. Time domain electric fields were recorded from tropical and temperate thunderstorms. PB pulses pertinent to the tropical thunderstorms are found to radiate in the average frequency range 51-739 kHz. Leaders are found to radiate in the frequency range 87-720 kHz. The energy radiated by the negative return strokes is predominant in the range 2.8-40 kHz. The energy radiated by the first subsequent strokes predominantly lies in the frequency range 4.5-55 kHz. Positive return strokes are found to radiate predominantly in the frequency range 5.5-81 kHz. Narrow bipolar pulses are found to predominantly radiate in the frequency range 58-714 kHz.
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| 14. |
- Sharma, S R, et al.
(författare)
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Unique lightning activities pertinent to tropical and temperate thunderstorms
- 2011
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Ingår i: Journal of Atmospheric and Solar-Terrestrial Physics. - : Elsevier BV. - 1364-6826 .- 1879-1824. ; 73:4, s. 483-487
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Tidskriftsartikel (refereegranskat)abstract
- Observations from two geographical locations show that some lightning events are unique and specific to the respective thunderstorms. From the measurements conducted in a tropical country, Sri Lanka, and a temperate country, Sweden, it is observed that there are some lightning activities that are unique for each location. Narrow bipolar pulses (NBPs) have frequently been observed in the tropical thunderstorms and were not observed in the temperate thunderstorms, whereas isolated breakdown pulses (IBPs) have frequently been observed in the temperate thunderstorms and were not observed in the tropical thunderstorms. It can be speculated that NBPs are the unique features of tropical thunderstorms and that IBPs are the unique features pertinent to the temperate thunderstorms.
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| 15. |
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| 16. |
- Vayanganie, S.P.A, et al.
(författare)
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High Speed Optical Observations of Cloud Flashes
- 2014
-
Ingår i: 2014 INTERNATIONAL CONFERENCE ON LIGHTNING PROTECTION (ICLP). - : IEEE conference proceedings. - 9781479935444 ; , s. 752-755
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Konferensbidrag (refereegranskat)abstract
- Luminosity variations of natural cloud lightning channels were studied using high speed video recordings in Sri Lanka in the tropic. Five cloud flashes were selected for the study, which were recorded with 5000 fps with 512X512 pixel resolution. Luminosity variation along channels and along selected channel segment, duration of cloud activities was studied. It was found that the average duration of selected flashes is 266.44 ms. No particular pattern was observed for the luminosity variation along channel segments. However the luminosity variation across the channel followed a Gaussian distribution pattern. Pattern of the luminosity variation along channels were compared with existing models to understand the development process of cloud flashes. Results show that it is hard to collaborate the observation to a single process for cloud discharges.
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