The main target was to check if ionospheric disturbances caused by seismogenic activity during the earthquake preparation process are simultaneously detected with cross correlation method using foF2 data provided by various observation points.
the critical frequency relates to peak ionospheric electron density or the highest value of the density as a function of height. It is thus a critical parameter in defining the ionospheric electron density profile that relates to seismic perturbations in ionospheric electron density.