부산대학교 도서관

The negative cloud-to-ground (CG) flashes that struck the ground with multiple contacts have been analyzed based on a high-speed video camera system (1000 frames s-1) in correlation with fast and slow antenna systems. Two cases have been divided. In one case, the CG flashes struck the ground with more than one termination on a millisecond-scale. This kind of stroke, named as multiple-ground termination stroke (MGTS). The other case was the lightning with different terminations in normal different return stroke process, and named as multiple channel flash (MCF). The percentage of the flashes with MGTS occupied about 15% (9 out of 59) in the total CG flashes according to the optical images from high speed video camera and the corresponding electric field recordings, while the percentage of the MCF occupied about 4%. While the tip of leader away from ground, the characteristics of pulses had no relation with the progress of several branches. But the electric field caused by multiple branches will change into cluster when the tip of leader nearing the ground.