Transparency change of the ionosphere for cosmic radio waves caused by acoustic pulse of ultra low frequency range

The simulation of the passage from the lithosphere through the atmosphere to the ionosphere of acoustic waves produced by seismic eruption or explosion shows that there is an acoustic coupling among these layers. This in turn is the cause of change in the transparency of the ionosphere for cosmic radio waves. Underground displacements produce Very Low (VLF) and Extremely Low Frequency (ELF) acoustic waves. In their passage through the lithosphere, the VLF wave is subject to nonlinearity that leads to frequency down-conversion, namely, increasing the ELF acoustic component at the Earth's surface. In turn, the nonlinear propagation of ELF acoustic wave in the atmosphere and the ionosphere leads to the emergence of ultra low frequency (ULF) acoustic waves in the ionosphere. An ultra low frequency acoustic wave (ULF) brings influence into the density of F-layer of the ionosphere and causes the transparency change of the ionosphere for cosmic radio waves.