Model of the First Lightning Return Stroke Using Bidirectional Leader Concept

We have developed a new lightning return stroke model which takes into account a realistic charge distribution to compute the ambient electric potential. It contains a nonlinear resistance model for the development of the finite conductivity of the lightning channel. It also describes a redistribution of charges after the bottom end of the channel is attached to the potential of the ground. The model is based on solving Maxwell's equations linked to Poisson's equation, and coupled with Ohm's law. The waveshape of the current at the channel base is obtained from the model. The simulated current decreases and its rise time increases with height, which is in accordance with the luminosity observations. The electric and magnetic field waveforms modeled for different distances from the lightning flash show that most of the waveform features typically observed at these distances are well reproduced. We also successfully compare modeled magnetic field waveforms with measurements at the distances larger than 30 km.