Q-Bursts in the Earth–Ionosphere Cavity with a Day–Night Non-Uniformity

The propagation of Q-bursts in the Earth–ionosphere cavity with a day–night non-uniformity is numerically simulated for the first time. The vertical conductivity profiles of the middle atmosphere differ from each other in the daytime and night-time hemispheres. The model of a smooth day–night transition in the ionosphere is used. The waveguide parameters in the ambient daytime and night-time conditions are computed using the full wave method in the form of a Riccati differential equation. These parameters are included in the numerically solved 2D telegraph equation (2DTE), thus providing complex spectra of the vertical electric field component. The solution obtained in the frequency domain is verified by comparison with published data. The sought waveforms of Q-bursts are computed using the inverse Fourier transform of complex spectra calculated in the 1–1000 Hz band with a 1-Hz step. Impact of the day–night non-uniformity is estimated by comparing the pulse waveforms on different propagation paths and using instant 2D field distributions in the Earth–ionosphere cavity. Time domain models of Q-bursts in the non-uniform Earth–ionosphere cavity were obtained for the first time. The day–night non-uniformity causes a time-dependent shift of the antipode pulse maximum from the geometric antipode of the source. A modulation of the amplitude of the negative and positive half-wave of a Q-burst in the vicinity of the ionospheric irregularity is observed. The pulse shape depends on its arrival direction relative to the terminator line. The character of variations in the waveform of Q-bursts indicates that solutions for the uniform cavity can be used for evaluating the source–observer distance in a real cavity. Prospects for experimental detection of the impact of the day–night non-uniformity on the shape of Q-bursts are discussed.