The Galileo spacecraft observed intense auroral kilometric radiation during the second Earth encounter in 1992. High-resolution frequency-versus-time spectrograms 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. These features may be due to impulsive wave generation and intrinsic velocity dispersion and/or a source stimulation by plasma waves traveling up the magnetic field line through the source region. We present several examples of these signatures, seen also on the Dynamics Explorer 1 satellite, and examine scenarios for their generation. ¿ American Geophysical Union 1996