The Galileo spacecraft observed intense auroral kilometric radiation during the second Earth encounter in 1992. High spectral resolution plots obtained by the wideband receiver of the plasma wave instrument on board the spacecraft often show discrete, negative-slope features each extending over a period of several seconds. Similar signatures are observed also in the DE-1 and Polar satellite wideband data. To date the features seem to be most commonly observed over the polar cap in a frequency range of 40 kHz < f < 100 kHz, but we cannot rule out observations of signatures at higher frequency. The frequency drift rates, R, are in the range −9.0 kHz/sec < R < −4.5 kHz/sec. A few cases of positive-slope features have been observed in the Polar data, and these show smaller frequency extents but larger drift rates in the range of 13 kHz/sec < R < 20 kHz/sec. The paucity of positiveslope features may be due to the location of the satellite at altitudes well above the AKR source region. We present evidence that suggests these features are due to AKR wave growth stimulated by the propagation of electromagnetic ion cyclotron waves travelling up (−R) or down (+R) the field line, through the source region.