Visual representation of high time resolution Auroral Kilometric Radiation (AKR) converted to audio. AKR is composed of many rapid combinations of rising and falling tones, sounding a bit like the R2-D2 robot in Star Wars.
Auroral Kilometric Radiation
The Wide Band (WBD) instrument on-board Cluster recorded this sound. Note that the original frequency range is outside the audible range but imposing an artificial frequency shift enables humans to hear them.