SAN FRANCISCO (AP) _ A satellite launched by a space shuttle has discovered surprisingly violent, continent-size windstorms in a rarely studied part of the atmosphere nicknamed the ''ignorosphere,'' a scientist said Thursday.

''They're like large ocean waves. They're very large - the size of the United States'' and bigger, said Paul Hays, scientist in charge of one of 10 instruments on the Upper Atmosphere Research Satellite.

The $740 million satellite was launched from Discovery on Sept. 15. It detected the global-scale windstorms 30 to 60 miles above Earth's surface when Hays' instrument started fully operating on Nov. 6 and 7, he said during the American Geophysical Union's fall meeting.

An ocean wave is relatively short in height on the open sea. But as it approaches a beach, the wave becomes taller and eventually breaks on shore. Hays said the newly detected, ''hellishly big'' windstorms are somewhat similar.

Weather in the lower atmosphere - called the troposphere - generates small wind waves that become bigger and bigger as they spiral upward through the stratosphere. Thin air in the next layer - the mesosphere - acts like a beach, making the wind waves break in turbulent 200-mph windstorms 600 to 6,000 miles wide, Hays said.

But the air that high is 1 million times thinner than at Earth's surface, so a person standing in the high-altitude wind wouldn't even feel them, he added.

The biggest storm spotted by the satellite stretches from western Australia across southern Africa and halfway across the Atlantic Ocean.

The mesosphere has been known as the ''ignorosphere'' because it is too high to be reached by airplanes and too low to studied by most spacecraft, said Hays, chairman of atmospheric, oceanic and space science at the University of Michigan.

''The mesosphere is a place that's hard to go to,'' he said. ''We've had measurements from rockets and radars and a few laser devices, but they've been spotty and sporadic.''

He said scientists expected to find small-scale, simple wind patterns sloshing back and forth in the mesosphere. ''Instead, we've seen swirling vortices of air that cover half the Southern Hemisphere,'' he said. ''They appear to rotate and pick up speed (as they rise through the atmosphere), eventually dissipating in massive turbulence like waves breaking on a beach.''

Rockets that released vapor trails in the mesosphere since the 1940s previously detected 200-mph winds at various spots, but the new satellite discovered the large-scale windstorm structure and pattern, he said.

Jim Holton, a University of Washington atmospheric scientist, called the discovery ''pretty exciting'' because it shows Cambridge University scientists were right in predicting that the wind waves would grow big and then break into huge turbulent storms in the mesosphere.

Holton said the region is called ''ignorosphere for more than one reason - it's an area most of us think has fairly minimal impact on civilization.''

But Hays said learning what happens in the mesosphere enhances our understanding of climate and what happens in the atmosphere below.

The Upper Atmosphere Research Satellite (UARS) orbits 363 miles above Earth. A telescope-like, light-detecting instrument called the ''high- resolution doppler imager'' looks down at the mesosphere to measure wind speeds in various directions.

It works on the principle that wind blowing toward the satellite looks slightly bluer, while wind blowing away looks a bit redder. It's the same principle that makes a departing train's whistle decrease in pitch.

The surprising windstorms were detected in data the satellite transmitted to the University of Michigan, where computers compiled the information into global maps on which scores of tiny arrows indicate wind patterns.

UARS was the first satellite launched in the National Aeronautics and Space Administration's Mission to Planet Earth, a decades-long study of Earth's environment from space. The satellite's major mission is to measure how pollutants are destroying the ozone layer, which protects people and crops from harmful ultraviolet rays.

Its other instruments measure those rays, atmospheric temperatures, energetic particles and the sun's brightness, among other things.