We analyze a long-lasting intracloud (IC) flash lasting >1800 ms using high-speed video and fast electric-field measurements from the Beijing Lightning Network. The flash entered the camera field of view from the left and developed horizontally toward the right and developed a horizontal channel; within ~100 ms, the channel progressively faded toward optical invisibility. During this period, multiple one-frame side discharges flickered along the already formed path. Following the connection of a side discharge to the established channel network, previously invisible channels were re-illuminated. Then, established channels repeatedly became nearly optically invisible and were subsequently re-illuminated, while other side discharges propagated outward and generated abundant new branches. The re-illumination switched between competing branches in a seesaw-like manner. We use a simplified potential model to interpret the observed branch-to-branch switching.

lightning,side discharge,continuing current