HR: 14:35h
AN: SA53C-03    [Abstracts]
TI: Strong ionospheric perturbations generated by powerful VLF ground-based transmitters
AU: * Parrot, M
EM: mparrot@cnrs-orleans.fr
AF: LPCE/CNRS, 3A Avenue de la Recherche Scientifique, Orleans, 45071, France
AU: Sauvaud, J
EM: sauvaud@cesr.fr
AF: CESR/CNRS, 9 avenue du Colonel Roche, Toulouse, 31028, France
AU: Berthelier, J
EM: jean-jacques.berthelier@cetp.ipsl.fr
AF: CETP, Observatoire de Saint Maur, 4 Avenue de Neptune, Saint Maur des Fosse, 94107, France
AU: Lebreton, J
EM: Jean-Pierre.Lebreton@esa.int
AF: ESA/ESTEC, Research and Scientific Support Department, Noordwijk, Netherlands
AB: This paper is related to the first in-situ observations of strong ionospheric perturbations close to powerful VLF transmitters. NWC in Australia is one of the most powerful VLF transmitters in the world and it is located at a low L-shell value (L=1.49). Waves and plasma parameters are recorded by the low orbiting satellite DEMETER. Electrostatic waves from HF to ELF ranges are generated and strong turbulence appears. Fluctuations of electron and ion densities are observed as well as increase of temperature. The perturbations are well located to the geographic North of the transmitter and cover a surface of ~ 500,000 km2. This area is centred at the altitude of the satellite (700 km) around the magnetic field line which has a foot at the location of the transmitter. This phenomenon is due to the electron and ion heating of the ionosphere induced by the powerful transmitter VLF wave. A much smaller effect is also observed in the Northern hemisphere at the conjugated location. This ionospheric perturbation observed for the first time is in addition to the already known precipitation of the energetic particles which interact with the VLF wave of the transmitter through a cyclotron resonance mechanism. NAA in US which has the same power as NWC is located at a much higher L value (3.0). Ionospheric perturbations from this transmitter is also detected although intense natural noise is present in this sub-auroral area.
DE: 2403 Active experiments
DE: 2435 Ionospheric disturbances
DE: 2471 Plasma waves and instabilities (2772)
DE: 2483 Wave/particle interactions (7867)
SC: SPA-Aeronomy [SA]
MN: 2007 Joint Assembly