The free screensaver, The Northern Lights of Jupiter, was created by RateMyScreensaver.com and contains 10 high resolution images. Both Jupiter and Saturn have magnetic fields much stronger than Earth's (Uranus, Neptune and Mercury are also magnetic), and both have large radiation belts. Aurora has been observed on both, most clearly with the Hubble Space Telescope. These auroras seem, like Earth's, to be powered by the solar wind. In addition, however, Jupiter's moons, especially Io, are also powerful sources of auroras. These arise from electric currents along field lines ("field aligned currents"), generated by a dynamo mechanism due to relative motion between the rotating planet and the moving moon. Io, which has active volcanism and an ionosphere, is a particularly strong source, and its currents also generate radio emissions, studied since 1955. - wiki Screensaver Picture Count: 10 Screensaver Type: Slideshow Credit: All images in this screensaver provided by NASA and the ESA