Electromagnetic model of M-components

M-components are transient enhancements of the channel luminosity occurring simultaneously with the continuing current phase of the cloud-to-ground lightning. They are initiated by the connection of the in-cloud channel to the grounded channel. We have developed a new model of M-component processes, which is based on the numerical solution of the Maxwell’s equations together with the Poisson’s equation for a given thundercloud charge structure. We compute the radiated electric and magnetic fields at various distances from the lightning channel. We model a microsecond-scale electric field pulse emitted during the connection of the in-cloud channel to the grounded channel and compare its waveform with measurements conducted in Florida. The modeled current waveforms at various heights above the ground are the outputs of our model and we compare them with measured luminosity curves. We also show how the M-component simulation results depend on the parameters of the model.