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Visible aurora on Saturn

Event Details

Event Dates: 

Monday, March 10, 2014 - 4:00pm

Seminar Location: 

  • JILA Auditorium

Speaker Name(s): 

Ulyana Dyudina

Speaker Affiliation(s): 

Caltech
Seminar Type/Subject

Scientific Seminar Type: 

  • Astrophysical & Planetary Sciences Seminar

Event Details & Abstract: 

Cassini camera detected Saturn’s visible-wavelength aurora in 2006-2013 in both the northern and southern hemispheres. The color of the aurora changes from pink at a few hundreds of km above the cloud tops to purple at 1000- 1500 km above the horizon. The spectrum observed in 9 filters spanning wave- lengths from 250 nm to 1000 nm has a prominent H-alpha line and roughly agrees with the laboratory simulated auroras. Auroras in both hemispheres vary dramatically with longitude. Auroras form bright arcs, sometimes a spi- ral around the pole, and sometimes double arcs at 70-75◦ both north and south latitude. Large 10,000-km-scale longitudinal brightness structures persist for more than 100 hours. This structures rotate together with Saturn. Besides the steady structure, the auroras brighten suddenly on the timescales of few minutes. Smaller, 1000-km-scale structures may move faster or lag behind Sat- urn’s rotation on timescales of tens of minutes. The persistence of the large longitudinal structure in two long observations in 2009 and 2012 allowed us to estimate its period of rotation of 10.65 ± 0.15 h for 2009 and 10.8± 0.1 h for 2012. The 2009 north aurora period is close to the north branch of Saturn Kilometric Radiation (SKR) detected at that time. The 2012 south aurora pe- riod is longer than any SKR periods detected at the time, but it is similar to the SKR period of the South branch of SKR periods in 2004-2008. I will discuss the relevance of those periodicities to Saturn’s internal rotation.