Published online 12 April 2001 | Nature | doi:10.1038/news010412-7

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Jupiter's got flare

An Earth-sized flash on Jupiter has planet-watchers baffled.

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Aside from its flashy red spot, Jupiter can also show off in other ways. Watching the north pole of the giant planet through the Hubble Space Telescope, scientists have witnessed the first Jovian auroral flare1 - the equivalent of our 'northern lights'.

Jupiter was known to be capable of producing auroral flares but one has never been spotted directly before. What's more, the sheer size, brightness and speed at which the flare came and went has planetary scientists baffled as to what gives Jupiter's aurora its energy.

"We were lucky," says Hunter Waite, the planetary scientist at the University of Michigan in Ann Arbor who led the study. His team were looking in exactly the right place -- the auroral oval, a permanent glowing ring around each of the planet's poles -- at exactly the right time, just as the flare erupted.

The flare, five times brighter than the auroral oval, covered an area over Jupiter's pole the size of Earth in a matter of minutes, and disappeared just as fast.

Earth's northern lights occur when electrons in the solar wind, ionized particles which stream out of the Sun into the Solar System, break through our planet's magnetosphere, interact with the upper atmosphere and give off their energy as light.

The eerie glow at Jupiter's poles is also caused by interactions between electrons and the planet's atmosphere, but the electrons are locals. Volcanoes on Jupiter's moon Io are thought to spew the particles into space, which then spiral towards their mother planet. They are energized by Jupiter's immensely strong magnetosphere, and release light at the auroral oval.

Waite suspects that fluctuations in the solar wind may trigger flares in Jupiter's aurora. But there is insufficient energy in the solar wind -- weak by the time it gets to Jupiter -- and Jupiter's magnetic field to drive a flash of light as fast and furious as the one Waite and his co-workers saw.

"Jupiter is a massive system, so this is one hell of a response," says Emma Bunce a planetary scientist at the University of Leicester in Britain. "To get the brightness that they saw, there has to be some kind of accelerating mechanism at work," she says.

Waite agrees that there must be something else behind the fireworks. "I think Jupiter has some internal tricks involved in this," he says. 

  • References

    1. Waite, J. H., Jr,et al. An auroral flare at Jupiter. Nature 410,787 - 7892001. | Article | PubMed | ISI |