DETECTION ON THE INTERCOSMOS-24 SATELLITE OF VLF AND ELF WAVES STIMULATED IN THE TOPSIDE IONOSPHERE BY THE HEATING FACILITY SURA

Results are presented of a satellite experiment on the detection of VL F and ELF waves excited by irradiation of the night ionosphere F regio n by the field of a nonmodulated powerful radio wave. The excited VLF and ELF waves have been detected at topside ionosphere altitudes h = 5 00-1000 km in the frequency bands 7.5 kHz < f < 15 kHz and 8 Hz < f < 1.5 kHz at distances less than 50-100 km from the centre of the magnet ic force tube passing through the heated spot of the ionosphere. The r egion of wave occurrence has well-defined boundaries. This points to p ropagation (guiding) of the observed low frequency waves along geomagn etic field lines. Possible generation mechanisms for the low frequency emission observed are discussed. It is shown that longitudinal ELF wa ves may be excited at altitudes of the topside ionosphere by beams of suprathermal electrons resulting from the action of a high-power radio wave on the ionosphere. These waves have a small group velocity in th e direction orthogonal to the magnetic field. Occurrence of ELF oscill ations detected onboard of satellite may be caused also by satellite m otion in spatially inhomogeneous electrostatic held, connected with ar tificial irregularities of plasma density and accelerated electron bea ms. Whistler waves in the VLF band may result from conversion of lower -hybrid oscillations excited in the reflection region of powerful radi o wave due to scattering by artificial small scale field-aligned irreg ularities. The whistlers generated can propagate to the satellite alon g artificial ducts formed within the disturbed magnetic force tube. (C ) 1998 Elsevier Science Ltd. All rights reserved.