Electromagnetic monitoring of ionospheric perturbations due to sun-spot activity and activation of earthquake sources in the lithosphere and the Earth's mantle

A brief historical outline is given of very-low-frequency (VLF) electromagnetic monitoring of large-scale ionospheric perturbations due to Sun-spot activity and perturbations associated with the activation of earthquake sources in the lithosphere and the Earth's mantle. Means of increasing the reliability of short-term predictions of seismic activity are recommended.