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Keywords:

  • Cassini;
  • Saturn;
  • UVIS;
  • ultraviolet aurora

Observations from the Ultraviolet Imaging Spectrograph Subsystem on NASA's Cassini spacecraft provide new detail about Saturn's aurora. The measurements, reported by Grodent et al., were made in August 2008 when the spacecraft was only 5 Saturn radii from the surface. They found two types of ultraviolet auroral substructures in the main ring of the emission—bunches of spots and narrow arcs—ranging in size from 500 kilometers to several thousand kilometers. The researchers suggest that the small-scale structures are associated with magnetic-field-aligned electrical currents in Saturn's upper atmosphere that result from fluctuations in plasma flow triggered by Kelvin-Helmholtz waves in the magnetosphere.