Modeling initial breakdown pulses of lightning flashes using a matrix inversion method

This study describes a new method for modeling the radiated electric field (E) of initial breakdown pulses (IBPs) of lightning flashes. Similar to some previous models, it is assumed that E pulses are caused by a current propagating along a vertical path, and an equation based on Maxwell's equations is used to determine E due to the current. A matrix inversion technique is used with the IBP radiation term of E to determine the IBP current waveform directly from far-field E measurements rather than assuming a parameterized current waveform and searching for appropriate parameters. This technique is developed and applied to observations of six previously modeled IBPs. Compared to the prior modeling, this matrix inversion method gives significantly better results, based on calculated IBP goodness of fit to the original E data. In addition, this model can match IBP subpulses along with representing the overall bipolar IBP waveform. This method should be useful for studying IBPs because once the IBP current is known, one can calculate other physical parameters of IBPs, such as charge moment change, total charge moved, and total power radiated. Thus, the more realistic IBP current waveform determined by this technique may offer new clues about the physical mechanism causing IBPs.