Pilots of high-altitude airplanes have for years reported sightings of immense red and blue blobs flickering briefly like ghosts in the sky above thunderstorms, extending for miles above the stratosphere.

Now scientists have caught thousands of examples on videotape and have gathered data suggesting that the flashes are mighty surges of energy between the lower atmosphere and the edge of space.

They call the lights blue jets and red sprites, and after reviewing a collection of new data in San Francisco yesterday, they said the spectacular celestial events may be vital in understanding atmospheric physics -- and may be dangerous to high-altitude aircraft or astronauts as they ascend to orbit.

But scientists attending the American Geophysical Union conference in San Francisco this week confess that they are basically baffled by the phenomenon.

"Every explanation has holes in it," said John Winckler, a professor of physics and astronomy at the University of Minnesota, who was among the first to document the events with a grainy video image in 1989. "We're in the beginning of a new aspect of science here."

Scientists call the biggest lights red sprites, which tower up to 60 miles into the night sky. Blue jets are smaller, pulsating lights that race upward from thunderstorms at more than 100,000 miles per hour. Until a short time ago, nobody knew about either, and scientists still are uncertain whether the same thing causes both sprites and jets.

Individual examples have been compared to immense angels, carrots, cauliflowers and octopuses hovering and glowing briefly in the thin, nearly unexplored fringe of atmosphere too high for airplanes to fly and too low for satellites to orbit.

While blue jets emerge upward from the crown of a storm, red sprites flicker far above them. A large thunderstorm may reach as high as 10 miles, or more than 50,000 feet, but the sprites usually do not start until about 20 miles up and extend for another 40 miles in height.

Several of the biggest sprites have red bodies with reddish, hairlike extensions on top and blue tentacles drooping below. Usually, each one lasts less than a hundredth of a second.

As long ago as the mid-1950s, Scottish physicist and Nobel Prize winner Charles T. R. Wilson noted that the huge electric discharges from thunderstorms should profoundly affect the upper atmosphere. But while pilots reported occasional strange lights over storms, the events went unconfirmed until high-speed video gear became available.

Technically, they occur in layers of atmosphere called the mesosphere and the thermosphere, well above the stratosphere. "That part of the sky has also been called the `ignorasphere,' for good reason," said Davis Sentman of the University of Alaska's Geophysical Institute. "We were ignorant of it."

Sentman presided over a session on the events during the week's geophysical meeting at the Moscone Center.

In June and July, a group observing from a hilltop in Colorado recorded dozens to hundreds of sprites per night over thunderstorms hundreds of miles away over Kansas. Airborne observatories with two small jets at about the same time recorded thousands more in storms over the Midwest. During one 67-minute period, 97 sprites were recorded, said Eugene Wescott of the University of Alaska.

Radio signals generated by the sprites, when played through an audio speaker, "sound like eggs hitting a griddle." Sentman said.

Among the urgent, unanswered questions is whether the sprites and jets pose a hazard to space shuttle astronauts whose route to orbit often takes them over thunderstorms in the Atlantic.

"I don't have a clue what causes these things," said Walter Lyons of the Mission Research Corp. in Colorado, which is studying the sprites and jets for NASA. "But on the other hand, I would not volunteer to be the first astronaut to fly through one."