Approximation of a double-peaked lightning channel-base current

Purpose - The purpose of this paper is to present a new function for approximating lightning channel-base currents which is useful in return stroke modelling and for calculating lightning electromagnetic fields and induced effects in conductive structures, installations and systems. Design/methodology/approach - The derivative and integral of the function are obtained analytically. Function parameters are calculated to approximate theoretically assumed or experimentally measured first stroke channel-base currents using least-squares method. The proposed expressions are useful for calculating lightning electromagnetic field using thin wire antenna approximation and lightning stroke models. Analytically obtained Fourier transform of the function is needed in the case of a lossy ground. Findings - The function can approximate both double and one-rise front waveshapes, so as faster and slower decaying tails. Some important function characteristics can be chosen prior to the approximation procedure, such as the current peak and rise-time to peak, which is an advantage in comparison to other functions from literature. Parameters can be calculated so to obtain the desired decreasing-time to half of the peak value; maximum current steepness due to analytically obtained derivative; charge transfer corresponding to the function integral; the specific energy corresponding to integral of the square of the function, etc. Research limitations/implications - This function can be used also for approximation of other impulse quantities of interest. Originality/value - The new proposed function for lightning current modelling is suitable for generalization of the procedure for computing electromagnetic fields and induced effects.