COMMENTS ON THE SIGNIFICANCE OF RETARDATION EFFECTS IN CALCULATING THE RADIATED ELECTROMAGNETIC FIELDS FROM AN EXTENDING DISCHARGE

Abdract: A cloud-to-ground lightning return-stroke channel is usually modeled as an extending line with one end fixed at ground. Return-stroke models describe how the current is varying with time along the line. The expressions for electric and magnetic fields due to retarded currents on a stationary straight wire antenna of fixed length have been derived in time domain previously (e.g., [l]). These general integral expressions can be used in lightning field calculations with suitable modifications to take into account retarded channel ength and possible current discontinuity at the discharge front. The radiation fields far from the channel are generally expressed in terms of the time derivative of the retarded channel current. For the Transmission Line (TL) model which is characterized by a current wave moving verticall