资源环境科技发展态势分析平台

We found two kinds of side breakdowns from the active horizontal negative channel in a positive cloud-to-ground flash. During the propagation of the negative leader in the field of view, some decayed negative branches were reactivated, and most of them promoted the propagation of advancing negative leaders. The reactivations extended outward from the edge of the negative leader channel with an average speed of 2.2 × 10⁶ m s⁻¹, but they produced no distinct VLF-VHF radiations, as confirmed by the lightning mapping results. The reactivations of decayed negative branches were different from recoil leaders in the decayed negative leader because we deduce the outward breakdown has changed its polarity. In addition, the negative channel that induced a downward positive leader was hot and conductive, as revealed by its brightness. The results indicate that disconnection or current cutoff on the negatively charged lightning channel is unnecessary for the inception of a downward positive leader.