Aurora are caused by the interaction of charged particles with a planet's
atmosphere as they spiral along the magnetic field lines. The light
generated by this interaction display different colors (wavelengths)
depending on which atoms in the atmosphere are excited. Jupiter's aurora
are seen generally in the ultraviolet and near infrared wavelengths.
Like the giant planet's other superlative properties, the aurora on
Jupiter are also the most intense seen in the solar system.
On Jupiter, auroral emission ions are seen in three distinct forms or regions - a main oval shape around the magnetic pole that remains steady and rotating with the planet, a polar aurora that is highly variable with time and location, and in the form of footprints of Jupiter's larger moons as distinct spots. The satellite auroral footprints are caused by the electrical currents produced at the satellites and moving along Jupiter's magnetic field. In the image above, three such footprints can be seen.
Jupiter Aurora imaged by the Space Telescope Imaging Spectrograph (STIS) on NASA's Hubble Space Telescope (STScI-PRC00-38, John Clarke, U of Michigan)
Juno carries several instruments that will inform us about the aurora and their controlling processes. The Juno spacecraft will sample both polar regions of Jupiter, as well as the equatorial region. Juno's particles and fields instruments will be able to measure the number of particles interacting with the atmosphere that generate the aurora. The UV images will provide visual context for the other data such as the plasma. Radio waves instruments will gather data to improve our understanding of how the charged particles are accelerated in Jupiter's magnetosphere.
Big Auroras on Jupiter
In March 2007, Gladstone and colleagues used NASA's Chandra X-ray Observatory to observe the Jovian aurora shown below overlaid on a simultaneous HST image. [More]