Correlation analysis between channel current and luminosity of continuous/continuing current process in an artificially triggered lightning flash

Using the simultaneous high-speed camera records and channel-base current records in an artificially triggered negative lightning, the correlation between channel-base current and integrated luminosity (IL) of air-ionized part of lightning channel is analysed. Depending on the current´s changing trend (ascending or descending), and the luminosity property of those pixels used in calculating IL from the high-speed camera records (including saturated pixel or not), the continuous/continuing current process is divided into Stage-A (saturated ascending stage), Stage-B(saturated descending stage), Stage-C(unsaturated ascending stage), and unsaturated descending stage (not considered here due to lack of data). The analysis shows that: (1) IL shows a linear correlation with the logarithmic value of current in both Stage-A and Stage-B. The regression parameters (intercept and slope) in Stage-B are higher than those in Stage-A, which means that corresponding to a same current value, IL in descending stage is higher than that in ascending stage. (2) There exists a significant linear correlation between the square root of IL and current in Stage-C, and in this stage the curve fitting model shows the best fitting effect among the three Stages. (3) For all of the three Stages, there exist significant positive correlation between the fitting effect and the threshold index used in the calculation of IL, and the more perpendicular the channel is to the ground, the better the fitting effect.