Ionospheric Layer Variability Prior to Strong Earthquakes During Quiet Geomagnetic Conditions

International audience; We report on electric field measurements recorded by the Electric Field Detector (EFD) and the Instrument Champ Electrique (ICE) onboard, respectively, CSES and DEMETER satellites. We study the variations of Very Low Frequency (VLF) ground-based transmitter signals detected by both satellites during periods of low solar and geomagnetic activities. We consider the variation of VLF power spectra density in the frequency range between few Hertz to 20 kHz. We emphasize on ionospheric disturbances associated to earthquakes occurrences. Such disturbances are linked to waves generated by coupling of neutral particles and electrons related, through the atmosphere, to lithospheric ground displacements. The main peculiarities of seismic ionospheric anomalies are summarized taken into consideration technical complementary of both satellites.