The first observations of Saturn ’ s visible-wavelength aurora were made by the Cassini camera .
The aurora was observed between 2006 and 2013 in the northern and southern hemispheres . The color of the aurora changes from pink at a few hundred km above the horizon to purple at 1000-1500 km above the horizon .
The spectrum observed in 9 filters spanning wavelengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with laboratory simulated auroras .
Auroras in both hemispheres vary dramatically with longitude .
Auroras form bright arcs between 70 ^ { \circ } and 80 ^ { \circ } latitude north and between 65 ^ { \circ } and 80 ^ { \circ } latitude south , which sometimes spiral around the pole , and sometimes form double arcs .
A large 10,000-km-scale longitudinal brightness structure persists for more than 100 hours .
This structure rotates approximately together with Saturn .
On top of the large steady structure , the auroras brighten suddenly on the timescales of a few minutes .
These brightenings repeat with a period of \sim 1 hour .
Smaller , 1000-km-scale structures may move faster or lag behind Saturn ’ s rotation on timescales of tens of minutes . The persistence of nearly-corotating large bright longitudinal structure in the auroral oval seen in two movies spanning 8 and 11 rotations gives an estimate on the period of 10.65 \pm 0.15 h for 2009 in the northern oval and 10.8 \pm 0.1 h for 2012 in the southern oval . The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation ( SKR ) detected at that time .