Modification Of Sporadic E-Layers Caused By Seismic Activity

Among all earthquake precursors, those related to electromagneticeffects are the most puzzling, and the many possible sources ofnoise are cause of lively controversies. A large number oflaboratory experiments clearly suggest that micro-fracturingis associated with the appearance of spontaneous charge production(electrification) and transient Electric or ElectroMagnetic (EM)Emission. Many electric and magnetic pre-seismic and co-seismiceffects have been reported in the past as well as ionosphericperturbations. The aim of this paper is to review some of theseionospheric perturbations performed in the former Soviet Union.The importance of sporadic E-layer formation is underlined.Statistical studies with the available observations are done.At the end, a physical model of lithosphere-ionosphere couplingis presented in order to explain the observations. This modeltakes into account the following effects at the Earthʹs surface:electric charge generation, emanation of radioactive gas,temperature variation, and surface vibration. It is shown thatthese effects can trigger sporadic E-layer formation.