Observations of intense electrostatic hiss bands in the source regions of auroral kilometric radiation

The source regions of Auroral Kilometric Radiation (AKR), as observed by the VIKING satellite, are usually characterized by steep gradients of the thermal electron density. On the polar and equatorial edges of these thermal density depletions, very intense bursts of broadband electrostatic noise are detected in a frequency range extending from the low frequency cutoff of the high frequency wave receiver (10 kHz) up to the neighborhood of the local electron gyrofrequency. The intensity of these bursts is at least of the same order of magnitude as the maximum intensity of AKR, which takes place in the center of the cavity. A possible link between the presence of the electrostatic bursts and the AKR generation mechanisms is investigated.