First in-situ observations of strong ionospheric perturbations generated by a poweful VLF ground-based transmitter

Abstract

This paper is related to observations by the satellite DEMETER of strong ionospheric perturbations close to the VLF transmitter NWC in Australia (L = 1.41). 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 located to the geographic North of the transmitter and cover an area of ∼500,000 km2 which is centred at the altitude of the satellite (700 km) around the magnetic field line at L = 1.41. The phenomenon is due to the electron and ion heating induced by the powerful transmitter VLF wave. This perturbation is in addition to the already known precipitation of energetic particles which interact with the VLF wave through a cyclotron resonance mechanism. The particle precipitation zone is located south of the transmitter at a slightly larger L-shell value (1.9). Copyright 2007 by the American Geophysical Union.