Observations of the connection of positive and negative leaders in meter‐scale electric discharges generated by clouds of negatively charged water droplets

Abstract

Detailed observations of the connection between positive and negative leaders in meter‐scale electric discharges generated by clouds of negatively charged water droplets are presented, and their possible implications for the attachment process in lightning are discussed. Optical images obtained with three different high‐speed cameras (visible range with image enhancement, visible‐range regular, and infrared) and corresponding current recordings were used. Two snapshots of the breakthrough phase of the leader connection, showing significant leader branching inside the common streamer zone, are presented for the first time. Positive and negative leader speeds inside the common streamer zone for two events were found to be similar. Higher leader speeds were generally associated with higher leader currents. In the case of head‐to‐head leader connection, the infrared brightness of the junction region (probably representing the gas temperature and, hence, the energy input) was typically a factor of 5 or so higher than for channel sections either below or above that region. In 16% of cases, the downward negative leader connected to the upward positive leader below its tip (attached to the lateral surface of the positive leader), with the connection being accomplished via a channel segment that appeared to be perpendicular to one or both of the leader channels.

Numerical Simulation of Stepping and Branching Processes in Negative Lightning Leaders

“…Sometimes between those two connections there are additional (attempted hot‐channel) connections (see Tran & Rakov () and references therein). Two current and light pulses have been documented during the attachment process in long negative sparks by Kostinskiy et al (, Figures 2 and 4).…”

“…Sometimes between those two connections there are additional (attempted hot-channel) connections (see Tran & Rakov (2017) and references therein). Two current and light pulses have been documented during the attachment process in long negative sparks by Kostinskiy et al (2016, Figures 2 and 4). Figure 7 shows the current and power density waves in different sections of the channel associated with a single step presented in Figure 6.…”

The Discharge Preceding the Intense Reillumination in Positive Leader Steps Under the Slow Varying Ambient Electric Field

“…Negative leaders propagate in discrete steps, with waiting time of tens of microseconds punctuated by sudden jumps (Berger, 1966;C J Biagi et al, 2014;Guimaraes et al, 2017;Hill et al, 2011;Reess et al, 1995;Malagón-Romero & Luque, 2019). The underlying mechanisms leading to the formation of negative leader steps were first discovered in laboratory discharges and only recently confirmed in natural lightning (Bazelyan & Raizer, 2000;Kostinskiy et al, 2016). Positive leaders usually propagate continuously but exhibit steps/restrikes characterized by intense reilluminations under the slow varying ambient electric field or at high moisture (Berger, 1966;Domens et al, 1991;Idone, 1992; V A Rakov et al, 2003;Marcelo M F Saba et al, 2008;Christopher J Biagi et al, 2011;Warner, 2012;Jiang et al, 2013;Wang et al, 2016;M.…”

Russian studies of atmospheric electricity in 2015–2018

“…Установлено, что скорости положительных и отрицательных лидеров внутри общей стримерной зоны совпадают и увеличиваются с ростом силы тока. Полученные результаты важны для решения фундаментальных проблем динамики главной стадии молнии [40]. В работе [41] впервые продемонстрирована возможность инициирования электрических разря-дов арбалетным болтом (снарядом), движущимся в электрическом поле облака отрицательно заряженных капель воды.…”