Fast evaluation of the lightning electromagnetic field in the time domain with an adaptive piecewise approximation of channel base current

Purpose - A fast algorithm is proposed to calculate the lightning electromagnetic field over a perfectly conducting earth surface. Design/methodology/approach - The channel base current is approximated by a number of sub-domain quadratic functions using the proposed adaptive sampling technique, and the derivative and integral of the channel base current with respect to time can be analytically expressed. With the help of these approximations, the ideal electromagnetic field of the lightning channel can be evaluated along the lightning channel with respect to the height. Findings - The computational time can be greatly reduced using the proposed approach to evaluate the electromagnetic field of a lightning channel in the time domain. Originality/value - The adaptive sampling technique is a general-purposed approach, which can be potentially used in other applications to fit a function with the minimal number of intervals.