Saturn’s aurora, whose reddish color is characteristic of ionized hydrogen plasma. Powered by the Saturnian equivalent of (filamentary) Birkeland currents, streams ofcharged particles from the interplanetary medium and solar wind interact with the planet’s magnetic field and funnel down to the polar regions. Double layers are associated with filamentary currents and current sheets, and their electric fields accelerate ions and electrons. Omage credits: Wiki Commons; J.Trauger (JPL), NASA, Hubble Space Telescope