Calculation of gain coefficient in Dwyer relativistic discharge feedback model of thunderstorm runway breakdown

Some of modern models used to describe TGF phenomenon and lightning ignition assume the existence of positive positron or gamma ray feedback. In this article we present some results of Monte-Carlo simulation of electromagnetic avalanches in atmospheric conditions and calculation of gain coefficient for both positron and gamma-ray feedback. The calculations were maid for realistic fields and acceleration cell sizes (up to 200 kV/m and 400 m respectively). The calculated gain coefficients for realistic fields and cell sizes are less than 10% which strongly discourages use of positron and gamma feedback model to describe TGF phenomenon and other gamma-production mechanisms in atmosphere under normal conditions. The simulation also shows possibility of selfsupporting positron feedback for extreme conditions like very high electric fields and very large cells