Simulation of seismo-ionospheric effects initiated by internal gravity waves

Experimental studies have repeatedly demonstrated that, a few days before a strong earthquake, local increases (sometimes decreases) in the electron density in the ionosphere over the epicentral area emerge. Simulations with the help of the GSM TIP (global self-consistent model "Thermosphere-Ionosphere- Protonosphere") and UAM (Upper Atmosphere Model) models show that account of local disturbances of the zonal electric fields makes it possible to reproduce the morphology of ionospheric disturbances. However, these model experiments do not explain the formation of such ionospheric features over the epicentral area of the impending earthquake. In this paper, we propose a mechanism for the formation of ionospheric disturbances before strong earthquakes due to propagation and dissipation of small-scale internal gravity waves (IGWs) in the upper atmosphere. Using the GSM TIP model, we calculated the ionospheric parameters with account of small-scale IGWs in the near-epicenter area. It is shown that disturbances in the TEC (total electron content) predicted by calculations are in satisfactory agreement with observations from GPS (Global Position System) satellites before the strong mid-latitude earthquake in Greece on January 8, 2006.