Luminosity and Current Characteristics of Metal-vaporized Channel of an Artificially Triggered Lightning

Channel current is an important parameter of the lightning discharge, but it's difficult to be directly measured due to the randomness and instantaneity of the natural lightning. The channel luminosity, however, is relatively easier to obtain. If there is a definite relationship between channel current and luminosity, the channel current can be estimated based on its luminosity. The correlation between the current and luminosity of lightning channel can be obtained through artificially triggered lightning experiments, during which the channel current can be directly measured and close-range optical observations of the lightning channel can be carried out.Base on observations of an artificially triggered lightning obtained at the Field Experiment Base on Lightning Sciences, China Meteorological Administration (CMA_FEBLS) in 2022, characteristic parameters of the channel-base current, the luminosity of the metal-vaporized channel, and their correlation are analyzed. The spatial movement of the metal-vaporized channel during the multiple return stroke processes is distinguished using still image with high spatial resolution. Combined with the high-speed video camera images and the channel current data, the correlation between the luminosity of the metal-vaporized channel and the channel current in the process of return strokes, and M components are studied. The results show that compared with the peak current, its squared value has stronger correlation with the peak luminosity for 13 return strokes. For the return stroke followed by a long continuing current, as well as the return stroke decay stage, both the current and M components superimposed on it show good linear correlations with the channel luminosity, with correlation coefficients of 0.981 and 0.988, respectively. However, the slope values of correlation fitting lines for the channel current versus the channel luminosity of the return stroke decay stage and the subsequent continuing current are obviously different. For M components superimposed on the long continuing current, a time delay for the peak luminosity relative to the peak current is revealed, and it is found that a smaller pulse peak current corresponds to a larger delay time.