September 24, 2010A new movie
and images showing Saturn's shimmering aurora over a 2-day period are helping scientists understand what drives some of the solar system's most impressive light shows.
The movie and images are part of a new study that, for the first time, extracts auroral information from the entire catalog of Saturn images taken by the visual and infrared mapping spectrometer instrument (VIMS) aboard NASA's Cassini spacecraft. These images and preliminary results are being presented by Tom Stallard, lead scientist on a joint VIMS and Cassini magnetometer collaboration, at the European Planetary Science Congress in Rome, Italy, Friday, September 24.
In the movie, the aurora phenomenon clearly varies significantly over the course of a saturnian day, which lasts around 10 hours and 47 minutes. On the noon and midnight sides (left and right sides of the images, respectively), the aurora brightens significantly for periods of several hours, suggesting the brightening is connected with the angle of the Sun. Other features appear to rotate with the planet, reappearing at the same time and the same place on the second day, suggesting that these are directly controlled by the orientation of Saturn's magnetic field.
"Saturn's auroras are very complex and we are only just beginning to understand all the factors involved," Stallard said. "This study will provide a broader view of the wide variety of different auroral features that can be seen, and will allow us to better understand what controls these changes in appearance."
Aurorae on Saturn occur in a process similar to Earth's northern and southern lights. Saturn's magnetic field channels particles from the solar wind toward the planet's poles, where they interact with electrically charged gas (plasma) in the upper atmosphere and emit light. At Saturn, however, auroral features can also be the result of electromagnetic waves generated when the planet's moons move through the plasma that fills Saturn's magnetosphere.