Characteristics of upward leaders from tall structures

The initiation models of upward leaders from tall structures are reviewed and the relationship between the equivalent height of a structure and upward leader occurrence is discussed. The observation results of propagation characteristics of upward leaders at a 200 m chimney in the coastal area of the Sea of Japan are shown with the corresponding current waveforms. From the observation results, we evaluated the line charge density of the upward leader. The line charge density of the upward leader is much larger than those predicted from the results of long spark experiments in laboratories.