Modeling of Return Strokes With Their Initiation Processes Under Consideration

Abstract

We developed an engineering return-stroke model specifically for studying the effects of return-stroke initiation processes. In the model, two current waves with identical wave shapes propagate upward and downward at two independent speeds from a height-variable return-stroke initiation point. Using that model and several results recently observed on the lightning return-stroke initiation processes, we have studied the electromagnetic fields produced by a return stroke at a horizontal distance from the strike termination point. It is shown that, depending on the front steepness of the current waveform, the presence of the downward return-stroke current wave may result in a visible initial peak in the rising portion of the return-stroke-produced field waveforms. A larger initiation height appears to result in an initial field peak with a larger amplitude, and also longer duration time. Moreover, a larger downward return-stroke speed tends to produce a sharper initial field peak.