Polarization and mode identification of auroral kilometric radiation by PWS system onboard the Akebono (EXOS-D) satellite.

Abstract

The first study of the Poynting flux of the auroral kilometric radiation (AKR) based on detected amplitudes and phase angle of waveforms has been carried out by the PWS (Plasma Waves and Sounder Experiment) onboard the Akebono (EXOS-D) satellite. With the clarified information on the propagation and polarizations, the propagation mode of the AKR was determined. The first results of the Poynting vector indicated that there is a case where the medium intensity AKR shows L-O mode propagation. The other results indicated that there is a case where sudden polarization reversal from the L-O mode to the R-X mode is associated with explosive AKR bursts. The electrostatic plasma waves were found near the local upper hybrid frequency in the source region. Though detailed studies are deferred for future studies, the evidence from the observation of the upper hybrid mode waves at the very source of AKR indicates a basic necessary condition for the conversion theory.The intensity and the direction of AKR Poynting flux vary even in a period of 10 milliseconds. The variation of this Poynting flux suggests very fast motion of the source location of AKR for their intense portion.