lightning induced EM field

I want to calculate the electromagnetic field radiated by lightning and get a graph in time domain using MATLAB .The lightning channel is considered as a vertical antenna of height H divided into n dipoles of length dz,the expressions for electric and magnetic fields are given in this paper

http://ijeit.com/vol%202/Issue%204/IJEIT1412201210_36.pdf

second page !!!

helppppppppppppp