The DEMETER mission, recent investigations on ionospheric effects associated with man-made activities and seismic phenomena

International audienceTwo of the main scientific objectives of the DEMETER mission concerned the search for ionospheric effects due to earthquakes and the study of disturbances associated with human activities or natural phenomena such as thunderstorms. The large data base gathered during nearly 6 years of in-orbit operation has lead to making new observations and/or to improving the understanding of several, already identified, phenomena. The main effects of human activities are observed in the field of radio-electric emissions and we present several results on the EM waves generated by power networks or associated with high power VLF transmitters. The search for ionospheric disturbances associated with earthquakes relies on thorough statistical studies to disentangle seismic effects from the variations induced by the physical processes that control the ionospheric plasma and natural emissions. Several studies are presented, and one of them has demonstrated a decrease of the ELF wave intensity in the frequency range between 1 and 2 kHz a few hours before the shock