Manifestation of Seismic Impacts in the Ionosphere Far from the Earthquake Epicenter

Abstract

Abstract: On the basis of the results of theoretical studies of the manifestation of seismic activity it was shown that as a result of the impact on the atmosphere and the neutral component of the ionosphere of the acoustic pulse caused by a Rayleigh surface wave, both in ground-based experiments and in satellite observations at heights of the F-region of the ionosphere the perturbations of the vertical velocity of the neutral component and electron density can be recorded, which leads further to the formation and evolution in the far zone of a solitary internal gravitational wave (IGW) and to the excitation by this wave of a traveling ionospheric disturbance (TID) with corresponding characteristic spatial scales, which propagate radially from the epicenter at angles close to the horizontal, with velocities of ∼200 ms−1. Consideration of the 3-dimensional case taking into account all significant factors (weak nonlinearity and dispersion, dissipation and stochastic fluctuations of the wave field) enabled us to refine the results previously obtained by other authors and showed that in the far zone from the epicenter of the earthquake the form of the ionosphere response to a seismic event depends significantly on the values ​​of the main parameters of the ionosphere, determining its dispersive characteristics, the fluctuation and dissipative processes in the region of propagation of the IGW and the excited by it TID: it can be a solitary wave disturbance, and a wave packet with characteristic IGW scales. It was found that that there is both a phase shift of the TID relative to the IGW phase (within 0.5–5 min), and the relaxation effect in the recovery of the electron density after the passage of the IGW soliton. The obtained results of the analysis of seismic-ionospheric post-effects, displaying in the formation of soliton-like IGW and TID disturbances in the far zone and representing a great interest, in particular, for a better understanding of causal relationships in the “solid earth–atmosphere–ionosphere” system, can be used for finding direction to the earthquake epicenters and distinguishing the seismic-induced oscillations in the spectrum of ionospheric fluctuations.