An improved method for calculating electromagnetic field in long distance radiated from lighting return stroke

In this paper, an improved analytical algorithm is proposed to calculate the long-distance electromagnetic field radiated from lightning return stroke. Based on the long-distance ideal electromagnetic field attenuation algorithm and the near-distance electromagnetic field attenuation algorithm, the curvature attenuation factor proposed by W. Sollfery is combined with the conductivity attenuation factor proposed by Wait. The two decay factors are convoluted twice by the ideal field to obtain the actual attenuation electromagnetic field in purpose of simplifying the calculation. The finite-difference time-domain is used to evaluate the algorithm. Results show that the error of the attenuation electric field is less than 7% in 1 500 km; while when calculating the magnetic field, the precision is inaccurate as the increase of length, and the error value can reach 15% when the length is 1 000 km. We plots the error curve, which can help people to consider the error range and decide to choose this formula or not.