Jupiter’s powerful auroral emissions cover a broad range in the photon spectrum ranging from radio emissions to ultraviolet (UV) and x-rays. UV observations suggest an auroral input flux power of 1013 – 1014 W mostly from the main auroral oval. The main oval emission is thought to be associated with upward electrical current on field-lines connecting to the middle magnetosphere where the plasma flow begins to lag behind co-rotation. Ultraviolet auroral emissions in the polar cap are much more time variable than the rather steady main oval emission and often exhibit flare-like behaviour. Time variable X-ray emission has also been observed from the poles with a power of about 1 GW. It is thought that this x-ray emission is due to the acceleration and subsequent precipitation of ions from the outer magnetosphere, perhaps linking to magnetic reconnection sites on the magnetopause. Observations of x-ray spectra show oxygen and sulfur lines from high charge state ions, which are explained by electron removal collisions (i.e. stripping collisions) with the atmospheric H2. Measurements to be made by instruments onboard the Juno spacecraft will shed light on the poorly understood polar aurora.
Published on January 24, 2014
Speaker:Tom Cravens (Kansas University)