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  • Jupiter, with satellites Io and Europa
    Jupiter, with satellites Io and Europa (Click on the image for a larger view)
    An electric current of 5 million amperes was detected in the flux tube that flows between Jupiter and Io, five times stronger than predicted. Voyager did not fly through the flux tube, as planned, since the stronger current had twisted the tube 7,000 kilometers (4,300 miles) from the predicted location.

  • The Voyagers saw ultraviolet emissions from doubly and triply ionized sulfur and doubly ionized oxygen. Pioneers 10 and 11 did not detect them, so hot plasma evidently was not present in 1973 and 74. The sulfur comes from Io's volcanoes.

  • Plasma-electron densities in some regions of the Io torus (an inner-tube-shaped ring of matter in the region of Io's orbit) exceeded 4,500 per cubic centimeter.

  • A cold plasma, rotating with Jupiter, lies inside six Jupiter radii (430,000 kilometers or 270,000 miles) from the planet. Ions of sulfur, oxygen, and sulfur dioxide were found.

  • High-energy trapped particles were also detected near Jupiter, with enhanced abundances of oxygen, sodium, and sulfur.

    Kilometric radio emissions were coming from Jupiter. The emissions, in the frequency range from 10 kilohertz to 1 megahertz, may result from plasma oscillations in the Io torus.

  • Plasma flows in the dayside outer magnetosphere; the plasma rotates with the planet every 10 hours.

  • Voyager 1 saw evidence of a transition from closed magnetic field lines to a magnetotail on the antisolar side ofJupiter. Although such a magnetotail was never in serious doubt, its existence had not been confirmed before.

  • Voyager 2 observations during its Jupiter-to-Saturn cruise showed the magnetotail extends at least to the orbit of Saturn, 650 million kilometers (400 million miles) away.

  • Scientists interpreted whistler emissions as lightning whistlers in the atmosphere. Lightning was suspected, and it has been proven, from the emissions and detection of bolts; lightning is a major energy source for many activities on Jupiter.

  • Voyager also measured radio spectral arcs (from about 1 megahertz to more than 30 megahertz) in patterns that correlate with Jovian longitude.

  • Both Voyagers continued on to encounters with Saturn. Voyager 1 is bound out of the solar system. Voyager 2 completed encounters with Uranus (in January 1986) and Neptune (in August 1989). It is now also leaving the solar system.
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