Unexpected Very Low Frequency (VLF) Radio Events Recorded by the Ionospheric Satellite DEMETER M. Parrot • J. J. Berthelier • J. Blecki • J. Y. Brochot • Y. Hobara • D. Lagoutte • J. P. Lebreton • F. Ne ˇmec • T. Onishi • J. L. Pinc ¸on • D. Pı ´s ˇa • O. Santolı ´k • J. A. Sauvaud • E. Slominska Received: 26 September 2014 / Accepted: 10 January 2015 Ó Springer Science+Business Media Dordrecht 2015 Abstract DEMETER was a low Earth orbiting microsatellite in operation between July 2004 and December 2010. Its scientific objective was the study of ionospheric perturba- tions in relation to seismic activity and man-made activities. Its payload was designed to measure electromagnetic waves over a large frequency range as well as ionospheric plasma parameters (electron and ion densities, fluxes of energetic charged particles). This paper will show both expected and unusual events recorded by the satellite when it was in operation. These latter events have been selected from the DEMETER database because they are rare or even have never been observed before, because they have a very high intensity, or because they are related to abnormalities of the experiments under particular plasma conditions. Some events are related to man-made radio waves emitted by VLF ground-based transmitters or power line harmonic radiation. Natural waves, such as aty- pical quasi-periodic emissions or uncommon whistlers, are also shown. M. Parrot (&) Á J. Y. Brochot Á D. Lagoutte Á J. P. Lebreton Á J. L. Pinc ¸on LPC2E/CNRS, Orle ´ans, France e-mail: mparrot@cnrs-orleans.fr J. J. Berthelier Á T. Onishi LATMOS/IPSL/UVSQ, Paris, France J. Blecki Á E. Slominska CBK, Warsaw, Poland Y. Hobara UEC, Tokyo, Japan F. Ne ˇmec Á O. Santolı ´k Faculty of Mathematics and Physics, Charles University in Prague, Prague, Czech Republic D. Pı ´s ˇa Á O. Santolı ´k Institute of Atmospheric Physics AS CR, Prague, Czech Republic J. A. Sauvaud IRAP, Toulouse, France 123 Surv Geophys DOI 10.1007/s10712-015-9315-5