A Comparison on the E‐Change Pulses Occurring in the Bi‐Level Polarity‐Opposite Charge Regions of the Intracloud Lightning Flashes

Abstract

We have compared the E‐change pulses occurring in the upper positive charge region (UPCR) and the middle negative charge region (MNCR) of 41 normal intracloud (IC) flashes. E‐change pulses can be roughly grouped into isolated pulses and pulse trains with both positive and negative polarities. Although isolated pulses occurred about equally in UPCR and MNCR, there were much more pulse trains in MNCR than UPCR. Overall, the average amplitude, rise time, half‐peak width, and fall time of isolated pulses (pulse trains) are 56% larger (115% larger), 31% faster (43% slower), 25% narrower (46% wider), and 26% shorter (62% longer) in UPCR than in MNCR. Interestingly, in the same charge region, positive and negative pulses share similar characteristics. Based on a typical well‐structured IC, it was found that the majority of isolated pulses in both UPCR and MNCR occurred at or close to the leader tips. In contrast, about 30% UPCR pulse trains occurred at or close to the tip, while the remaining 70% pulse trains occurred in the leader channel retracing along the leader channel away from the flash origin; for MNCR pulse trains, about 60% occurred close to the tip, and 40% occurred in the channel with a backward extension to the flash origin. Based on these characteristics, we have discussed the physical nature of various types of pulses and pointed out that a leader is likely to progress with a fluctuating behavior when it is neutralizing space charge distributed in a region with sufficient thickness and width.

Initial Results of Long-term Continuous Observation of Lightning Discharges by FALMA in Chinese Inland Plateau Region

“…To better understand such a difference, Figure 13 shows the spatiotemporal distributions of all located sources, along with the upper and the lower heights of 95 well-mapped PB processes, for an isolated summer thunderstorm observed also by FALMA in Gifu, Japan [17,23]. All the PB processes belonged to IC flashes and propagated upward with their lowest sources at the height of around −10 • C and highest sources at around −40 • C. As has been reported recently, PB processes are a type of negative leader (see, e.g., [23,24]); such types of upward PB progressions indicate that the main negative charge in the thundercloud is at a height of around −10 • C (at a lower height) and the main positive charge is at a height of around −40 • C (at an upper height). This is a typical charge structure for summer thunderstorms in lowland areas.…”

“…The large observed percentage of the downward PB processes (August 2nd: 93%, 287/310; August 5th: 96%, 318/332) indicates that the charge structures of the thunderclouds were generally different from the ordinary summer thunderstorms in lowland areas (e.g., in [23,24]). To better understand such a difference, Figure 13 shows the spatiotemporal distributions of all located sources, along with the upper and the lower heights of 95 well-mapped PB processes, for an isolated summer thunderstorm observed also by FALMA in Gifu, Japan [17,23].…”

“…The large observed percentage of the downward PB processes (August 2nd: 93%, 287/310; August 5th: 96%, 318/332) indicates that the charge structures of the thunderclouds were generally different from the ordinary thunderstorms in lowland areas (e.g., in [23,24]).…”

“…As shown in [17], using FALMA, a detailed 3D mapping for lightning flashes occurring inside the network can be produced. The estimated horizontal location accuracy for RSs was around 20 m. More information about FALMA and the results obtained in Japan with FALMA can be found in [19][20][21][22][23][24].…”

Recoil Leader and Associated Discharge Features Observed During the Progression of a Multi‐Branched Upward Lightning Flash

“…When a discharge is progressing in a region with space charge, it usually involves many branches (e.g., Mazur et al, 1998). So, we speculate that the discharge features observed in this paper should be very common in lightning discharges inside clouds and the connection processes involved could produce the isolated E-change pulses with various rise times as observed by Shi et al (2020).…”