Calculation of Atmospheric Spectra Signals Propagation on the Earth-Ionosphere Wave-Guide over Seismoactive Regions

Abstract

For remote monitoring of parameters of the bottom ionosphere over seismoactive regions the VLFsignals from radio stations are widely used. It is witnessed that there are ionospheric disturbances over the epicenter of earthquakes both during lithospheric disturbances and before it (precursor). For reliability the use of pulse VLFsignals from lightning discharges – atmospherics is suggested. The disturbance in the bottom ionosphere, caused by lithospheric processes, is mainly expressed in the form of increase of the electron concentration and height of the «earth–ionosphere» wave guide. The change of parameters of the ionosphere leads to changes of a condition of propagation of a signal in the wave guide. Modelling consideration of amplitude-spectral variations of the low-frequency signals extending in the earth–ionosphere wave guide at occurrence of seismic disturbances on the top wall of wave guide (the lower ionosphere) is carried out. By the results of a comparison with experimental data of VLF-signal observation, possible characteristics of seismic disturbances in the lower ionosphere causing observable amplitude variations of signals are considered. It is established that the variations in the amplitude of the signals passing over the earthquakes will be due to a change in the steepness of the electron concentration profile and, to a lesser extent, the change in the height of the waveguide.