Auroral 'Star Wars'

"Sound of an Auroral Kilometric Radiation (AKR) collected by Cluster resembles the one of R2D2, the little robot from 'Star Wars'.

Earth can generate radio emissions in a natural way. The most intense of these emissions is a phenomenon called Auroral Kilometric Radiation (AKR). It is produced in the auroral zones at an altitude between 3000 and 20 000 kilometres. Afterwards, the sounds escape outward in the space from the magnetic field lines. AKR intensifies during magnetic and auroral substorms so you can use it as a remote indicator of geomagnetic activity. The Wide Band (WBD) instrument on-board Cluster recorded this sound and made the first direct determination of the locations of an AKR (courtesy of Prof. D. Gurnett, University of Iowa)."

Source credit: http://www.esa.int/Our_Activities/Space_Science/Sounds_from_space