A FDTD Lightning Return Stroke Model and its Application to Triggered-Lightning Data

FDTD method has been widely used in calculations of electromagnetic fields produced by a lightning return stroke and its effects on other systems. However, the traditional Pi-type distributed resistance (R) - inductance (L) - capacitance (C) model representing a lightning return stroke is no longer suitable for FDTD method. In this study, we propose a new type RLC model that consists of a current source at the lightning channel base feeding a series of passive RLC loads above. The model is then applied to two sets of channel base currents and multi-station electric field measurements from two return strokes in rocket-triggered lightning experiments. By fitting the simulated electric field with the measured electrical field at each station, an optimal set of lightning channel RLC values for each of the two return strokes were determined, and hence the current propagation speed and amplitude as a function of the channel height are successfully estimated. The results are well consistent with optical observations and physical model predictions.