British Antarctic Survey | 20 Oct 2010
Scattering by chorus waves as the dominant cause of diffuse auroral precipitation - RM Thorne et al
Scientists have long understood that the ‘diffuse aurora’ is caused by electrons striking the upper atmosphere. However, the electrons are normally trapped much higher up in the Earth’s magnetic field through a long chain of events starting with the Sun. The problem is to understand how these electrons reach the atmosphere.
Since the 1970s scientists have debated whether very low frequency (VLF) radio waves could scatter the trapped electrons into the atmosphere. Two types of VLF waves were identified in space as the possible cause of the ‘diffuse aurora’, but despite years of argument and research no conclusive result had been possible. The new research shows, without doubt, that VLF waves known as ‘chorus’ are responsible; so-called since the signals detected by ground-based recording equipment sound like the bird’s dawn chorus when played back through a loud speaker.
Through detailed analysis of satellite data the authors were able to calculate the effects on the trapped electrons and identify which radio waves were causing the scattering.
- Nature 467 943 (21 Oct 2010) DOI: 10.1038/nature09467
Space.com | 20 Oct 2010