Chaotic Pulse Train in Cloud-to-Ground and Cloud Flashes of Tropical Thunderstorms

Ahmad, Mohd Riduan and Mohd Esa, Mona Riza and Johari, Dalina and Ismail, Mohd Muzafar and Cooray, Vernon (2014) Chaotic Pulse Train in Cloud-to-Ground and Cloud Flashes of Tropical Thunderstorms. In: ICLP, 13-17 October 2014, Shanghai, China. (In Press)

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In most cases, the event of chaotic leader is often observed to precede natural subsequent return strokes [Weidman, 1982; Bailey et al., 1988; Willett et al. 1990; Rakov and Uman, 1990; Davis, 1999; Gomes et al., 2004; Mäkelä et al., 2007; Lan et al., 2011] and triggered subsequent return strokes [Hill et al., 2012]. The average pulse duration, inter pulse duration, and train duration have been reported to be about a few microseconds, 2-20 μs, and 470 μs, respectively. The range of the train duration is between 0.1 and 2 ms. It is suggested that chaotic leader event is associated with the dart leader process due to fact that chaotic leader is followed by a dart leader or dart stepped leader in most cases. On the other hand, Gomes et al. (2004) have reported the occurrence of chaotic leader in cloud flashes (IC) and in some cases it occurred in isolated breakdown (IB) flash, which suggest that perhaps chaotic leader associates with cloud activity rather than dart/dart stepped leader process. Because of this, Gomes et al. (2004) have used the term chaotic pulse train (CPT) rather than chaotic leader. In this paper, we report for the first time the observation of CPT preceding natural subsequent negative return strokes and also CPT occurrence in IC flashes from tropical thunderstorms in Malaysia. Electric field change measurement has been conducted in Southern Malaysia (latitude 1°34ʹ′12.00ʺ″N, longitude 103°38ʹ′42.00ʺ″E) during Northeastern monsoon season between November and December 2012. We examined 20 negative cloud-to-ground (CG) flashes and 9 cloud flashes. All 20 CG flashes are located within the range between 6 and 45 km and CPTs have been observed to occur between return strokes in 17 CG flashes only. A total of 73 CPTs have been recorded with the total number of CPTs between RS1 and RS2 is the highest, about 41.1% from the total 73 CPT as shown in Fig. 1. As for IC flashes, 6 are located within the range between 9 km and 67 km. 5 CPTs have been found to occur between IC flash pulses in all cases observed by us. In Fig. 2, an example of IC flash shows that it consists of a single CPT that is followed by a train of negative bipolar pulses and then immediately followed by a train of positive bipolar pulses superimposed on a slowly varying negative field change.

Item Type: Conference or Workshop Item (Poster)
Subjects: Q Science > Q Science (General)
Divisions: Faculty of Electronics and Computer Engineering > Department of Computer Engineering
Depositing User: En. Mohd Riduan Ahmad
Date Deposited: 19 Jun 2014 03:03
Last Modified: 28 May 2015 04:26
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