A STATISTICAL-SURVEY OF ELF WAVES IN A GEOSTATIONARY ORBIT

GEOS 2 is a geostationary satellite that was launched with a wave expe riment. The data provided during its lifetime (approximately 3.5 years ) constitute a unique set for the statistical study of electromagnetic and electrostatic waves at L = 6.6. The aim of this paper is to prese nt maps of the average intensity of the electric and magnetic field. T he location of the more intense emissions up to 4.6 kHz is shown as a function of local time and frequency. Such emissions are mainly compos ed of hiss, chorus and electron-cyclotron harmonic (ECH) waves. Their locations were specified and compared with data from the OGO 5 and SCA THA satellites. In particular, this study highlights the characteristi cs of chorus emissions with a gap at half the electron gyrofrequency. It is also shown that global magnetic activity only slightly influence s wave amplitude.