The luminescence characteristics and propagation speed of lightning leaders

The light intensity and 2-D propagation speed of the leader channel of natural lightning are obtained by analyzing the optical data captured by a high-speed camera. For the leader channels of cloud-to-ground (CG) lightning, attempted CG lightning and bidirectional leader lightning, the light intensities present a pulse at the positions where the tip of the leader arrived, and as the tip passed, the pulse disappear and the light intensities of the channel remain stable. As the stepped leaders approach the ground, the tip luminous intensities and two-dimension (2-D) propagation speed of the channels as a whole shown the tendencies of “increased”, “decreased” and “irregular” with time. Moreover, the luminous intensities of the tip or total channel increase when the branch occurred, while the propagation speed of stepped leader decreases in most cases.