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17 Jun 2002
Hubble Space Telescope's sharp view of the rapid, spectacular dance of luminescent gasses high in Jupiter's atmosphere -- better known as aurora -- is allowing astronomers to map Jupiter's immense magnetic field and better understand how it generates such phenomena.
The new Hubble observations simultaneously show warped oval rings at the north and south poles (offset from Jupiter's spin axis by 10-15 degrees), as well as an auroral "footprint" created by a river of electrical current of about one million amperes flowing between Jupiter and the volcanic moon Io. Changes in brightness occur over the course of a Jovian day, perhaps due to compression of Jupiter's magnetic field on the sun-facing side of the planet, researchers say. They also find emission features that are fixed on the planet, co-rotating with it. "The size of the aurora at the magnetic footprint of Io is 600 to 1,200 miles (1,000 to 2,000 kilometers) across," said John T. Clarke, an astronomer at the University of Michigan's College of Engineering.. "If you were at Jupiter's cloud tops, under Io's footprint, the aurora would fill the entire sky. You would see an explosion as the gasses 250 miles above you rapidly heated to more than 10,000 degrees Fahrenheit. The aurora would speed overhead from east to west at more than 10,000 miles per hour (5 kilometers per second) because Jupiter's fast rotation moves it rapidly underneath Io, which orbits more slowly."
Additonal pictures may be found at the URL listed below.
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