Correlation between Neutral Density Variation and Optical Emission Accompanying Streamer Progression upon Application of a Lightning Impulse

Abstract

Neutral density variations accompanying progression of streamers, which occur upon application of lightning impulse to an air gap, were observed using laser interferometry. The optical emission accompanying streamer progression was monitored simultaneously. In the case of positive polarity, the spatial distribution of neutral density variations and optical emission showed high correlation. In the case of negative polarity, the correlation was substantially lower, and neutral density variations were often observed when optical emission from the corresponding region was absent. The results showed that the corrlelation between the spatial distributions of neutral density variations and of optical emission differs largely according to the polarity.