Hot plasma channel network formation in thunderclouds

Abstract

The main intrigue of lightning initiation is that electric fields measured in thunderclouds have peak values about an order of magnitude lower than the dielectric strength of air and do not even exceed the minimum field needed for positive streamers propagation. It was recently established that pronounced decimeter-scale electric field fluctuations appear against the background of a relatively weak thundercloud large-scale electric field owing to turbulent mixing and polarization of hydrometeors. In the course of thundercloud development these field enhancements reach a level sufficient for initiation of positive streamers and their propagation over the distances of the order of decimeters. Streamers initiate, develop, decay, and merge with each other, thereby providing the appearance of an extensive hierarchical system of interacting plasma channels at different stages of development with embedded and growing hot segments. In this study the renormalization group approach is employed to calculate the value of thundercloud electric field that provides hot plasma channel network explosive formation. The calculated threshold field is considerably less than the minimum field required for positive streamers propagation and may be viewed as the true lightning initiation field.