Electrodynamic Model of the M-components and K-changes

M-components are transient enhancements of luminosity which occur during the intervals of the continuing current from the cloud to the ground. Two types of M-components have been previously identified: The first one is defined as an interception of the in-cloud channel by a continuing current channel and the second one is given by the extension of the upward positive channel following the return stroke processes. K-changes are step-like changes of the electrostatic electric field produced by propagating discharges similar to dart leaders. They carry a negative charge along a channel previously ionized by a negative leader. We model the second type of the M-component and K-changes by an electrodynamic model which solves the complete set of Maxwells equations coupled to Ohms law. We take into account a realistic thundercloud structure by solving the electrostatic Poissons equation. We propose that both the second type of the M-components and K-changes can be modeled by moving the lightning channel toward a small in-cloud charge pocket. We assume a vertical lightning channel and for the M-components, the channel at the ground level is placed at the ground potential. We compare the modeled electric field waveform of both M-components and K-changes with measurements. We show the modeled M-component currents at the bottom of the channel and compare them with luminosity observations.