The electrodynamic model of the return stroke processes involving a bipolar leader scheme

We have developed a new electrodynamic return stroke (RS) model, which is based on solving the full set of Maxwell’s equation together with the electrostatic Poission’s equation for a realistic thundercloud charge structure. The evolution of the line conductivity of the RS channel is characterized by a nonlinear resistance model. The RS channel consists of a vertical channel connecting the ground with the thundercloud and a horizontal in-cloud channel. The RS processes are initiated by adding a zero potential element into the bottom end of the vertical channel. The channel-base current does not have a predefined form, but results from our model. We show the comparison of the modeled magnetic field waveforms with the observations at distances of tens of kilometers from their source lightning discharge. We also verify the simulated electric and magnetic field RS waveforms at shorter distances and compare them with their typical shapes found in the literature. The line charge density and the electric potential prior to and after the RS initiation are also investigated from the point of view of the bidirectional leader concept.