Ulysses Soars Over Sun's North Pole

The Ulysses spacecraft flew over the sun's North Pole on January 14, 2008, just a week after physicists announced the beginning of a new solar cycle.

"This is a wonderful opportunity to examine the sun's North Pole at the onset of a new solar cycle," said Arik Posner, NASA Ulysses program scientist. "We've never done this before."

Launched from space shuttle Discovery in 1990, Ulysses is able to fly over the sun's poles and look down on regions that are difficult to see from Earth. The spacecraft previously flew over the sun's poles in 1994-95, 2000-01, and 2007.

"Just as Earth's poles are crucial to studies of terrestrial climate change, the sun's poles may be crucial to studies of the solar cycle," explained Ed Smith, Ulysses project scientist at NASA's Jet Propulsion Laboratory.

Many researchers believe the sun's poles are central to the ebb and flow of the solar cycle. When sunspots break up, their decaying magnetic fields are carried toward the poles by vast currents of plasma. This makes the poles a sort of "graveyard" for sunspots. Old magnetic fields sink beneath the polar surface 124,000 miles deep (200,000 kilometers), where the sun's inner magnetic forces may amplify them for use in future solar cycles.

During the most recent solar cycle, the sun's North Pole was about 80,000 degrees or 8 percent cooler than the South Pole. The most recent Ulysses flyby may help solve this puzzle, coming less than a year after the spacecraft's South Pole flyby in February 2007. Mission scientists will be able to compare temperature measurements, north vs. south, with hardly any time gap between them.

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