Auroras on Saturn, Uranus, and Neptune

Abstract

Aurorae result from the generation of emissions from the high latitudes of a planet due to the precipitation of energetic charged particles from the planet's magnetosphere. Auroral emissions from the outer planets have been observed from the ground, Earth-orbiting satellites, flyby spacecraft, and orbiter-based instruments at X-ray, UV, visible, IR, and radio wavelengths. The UV and IR are atmospheric emissions, produced when atmospheric species are excited by the precipitating particles, while radio and X-ray are beam emissions, produced by the precipitating species themselves. The emissions at different wavelengths provide unique and complimentary remote-sensing information about the key processes at auroral latitudes, and the planetary magnetospheric regions where they originate. This paper summarizes our current knowledge of auroras on Saturn, Uranus, and Neptune, as revealed by multi-spectral observations and supplemented by plasma measurements, and compares them with the Jovian aurora.