| A correlation between channel-base current and integrated luminosity(IL) of air-ionized part for initial continuous current(ICC) process and a relative long continuing current(CC) process is analysed by use of the simultaneous high-speed images and current records in an artificially triggered negative lightning. Depending on whether the current is ascending or descending and whether the major contributing pixels of IL of high-speed images are saturated or unsaturated, ICC process and CC process are divided into Part-A(saturated ascending stage),Part-B(saturated descending stage) and Part-C (unsaturated ascending stage), while unsaturated descending stage won't be considered separately because of lack of data. The analysis shows that: Firstly, there is linear correlation between IL and logarithmic value of current in both Part-A and Part-B, but the regression parameters (intercept and slope) in Part-B are higher than that in Part-A, which means IL in Part-B is greater than that in Part-A with the same current value. Secondly, there is significantly linear correlation between square root of IL and current in Part-C, and the fitting effect of Part-C is the most satisfactory in curve fitting models of IL and current. Finally, there is significant positive correlation between the fitting effect of each part and the threshold value of IL, and that the more perpendicular the channel is to the ground, the better fitting effect becomes.
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