资源环境科技发展态势分析平台

A numerical model with physical timing and grid spacing of 3 m is applied to studying the progression (including stepping and branching) of negative lightning stepped leader. The asymmetry between positive and negative streamers is taken into account via using polarity-dependent initiation and propagation field thresholds. The stepped nature of negative leader is confirmed to be caused by this asymmetry. The step formation process of the negative leader is modeled to begin with the appearance of space stems inside and in the immediate vicinity of its streamer zone (corona streamer burst completing the preceding step). Some of those space stems evolve into space leaders, which can connect to the primary leader channel, thereby facilitating its extension. Model-predicted morphology and dynamics of negative leaders are in good agreement with the recent recordings of lightning stepped and dart-stepped leaders obtained using high-speed video cameras, and their electrical parameters are in line with the current knowledge on negative lightning leaders.