Numerical simulation of lightning channel reactivation in recoil leader process

Abstract

Lightning development involves transient events that produce non-stationary, abrupt changes in lightning structure. The most prominent (and most studied) examples of reactivation of lightning side branches are recoil leaders that are initiated near the tips of previously decayed positive leader channels. This study proposes a numerical model that, among other things, takes into account evolution of channel temperature profile and is aimed at simulation the recoil leader inception. The model is based on the paradigm of reversal point meandering, which is a consequence of the macroscale asymmetry of development of positive and negative lightning poles. Simulation results allow one for the first time to formulate a physically-based and well-founded mechanism of a negative recoil leader initiation. In particular, it is shown that the channel reactivation is provided by the wave of electric field that starts from the branching point and propagates along a previously decayed (but still heated) leader channel when its per-unit-length resistance does not exceed several thousand Ohms per meter. This resistance corresponds to the channel temperature no less than $\sim$3500 K under equilibrium conditions. It is shown that channel reactivation starts somewhere between the branching point and the previously decayed leader tip, in agreement with observations. Additionally, the plasma chemical aspects of the leader channel reactivation are discussed.