Modeling of X‐ray emissions produced by stepping lightning leaders

Abstract

AbstractIntense and brief bursts of X‐ray emissions have been measured during the stepping process of both natural cloud‐to‐ground (CG) and rocket‐triggered lightning flashes. In this paper, we investigate theoretically the energy spectra of X‐rays produced by the bremsstrahlung emission of thermal runaway electrons accelerated in the inhomogeneous electric field produced around lightning leader tips. The X‐ray energy spectrum depends on the physical properties of the associated lightning leaders. Consequently, X‐ray measurements can be used for diagnostics of the electrical properties of lightning stepped leaders. We report simulation results of the photon energy spectra produced by 5 and 10 MV negative CG lightning discharges that would be measured from the ground using ideal detectors. We also quantify theoretically the radial dependence of X‐ray energy spectra received at ground level during the leader stepping process. Moreover, it is found that the ground radiation generated in this process is harmless to humans.