Monte Carlo Simulations of Nanosecond Electromagnetic Pulse Interaction With Field‐Aligned Ionospheric Plasma Density Irregularities

Abstract We propose an approach to simulate ultra‐wideband (UWB) electromagnetic pulse (EMP) propagation in the ionosphere with magnetic field‐aligned irregularities of plasma density based on Monte Carlo technique. This approach considers propagation of a nanosecond EMP by ray trajectories in the frequency domain, which allows one to analyze the role of scattering effects for lower and higher harmonics of the pulse. Parameters of the irregularities used in the simulations are chosen close to those of artificial ionospheric turbulence (AIT) density striations stimulated by high‐frequency (HF) heating facilities. The employed technique provides a possibility to compare the effects of dispersion and scattering on the waveform of bipolar nanosecond EMP for various parameters of ionospheric plasma and its disturbances. In the presence of 10‐m scale, 10‐percent level density striations, we show that lower frequencies are most responsible for the EMP waveform transformation due to the plasma dispersion, and are scattered away from the initial propagation direction, while higher frequencies experience minor dispersion and are less scattered. The influence of AIT‐type striations on the straightforward EMP delay and its broadening in the time domain is analyzed compared to the EMP propagation in uniform plasma. Preliminarily, the effects of AIT‐type striations on EMP characteristics seem to be weak in the main part of its frequency spectrum, even for strong (non‐realistic) plasma density depletions of up to 50%.