Numerical simulation of reversal point dynamics in intracloud lightning: Back-and-forth promoting effect

Abstract

Lightning is a self-developing charge transport system that exhibits fundamental manifestations of the macro-scale polarity asymmetry. This asymmetry is tightly connected with peculiarities of the reversal point (the point of zero leader sheath charge or, alternatively, a site where the lightning channel potential coincides with the intracloud one) movement along the leader growth direction. The study presents a stochastic lightning discharge model that is used to analyze the reversal point dynamics. It is shown that the reversal point shifts towards the direction of growth of the dominant leader, i.e. the leader with prevailing peripheral current. The cases of upward and downward directions of the positive leader propagation are considered to study how the difference in altitudes of positive and negative lightning poles influences the mode of reversal point drift. The model predicts that, for the case of an intracloud lightning, the amplitudes of oscillation of reversal point altitude and voltage are of the order of 1 km and 100 MV, respectively, with the reversal point voltage change rate being of the order of 10 MV/ms. The results allow to conclude that the reversal point meandering is a fundamental manifestation of lightning evolution.