Enigmatic bursts show their true colors.

High above the tops of thunderstorms, flashes of light dance like sprites in Earth's atmosphere. For the first time, researchers have captured the true colors of these scintillations -- red bursts resembling jellyfish and blue ones shaped like flaring trumpets.

Though the bursts reveal an electrical link between the ionosphere and the atmosphere's lower depths, their origin remains a mystery Adding to the puzzle, other scientists have noted a possible correlation between thunderstorms and flashes of gamma rays and radio waves.

Scientists confirmed the visible-light flashes last year. Flying over the Midwest, they videotaped in black and white several bursts above storm clouds.

This June 28 through July 12, Davis Sentman and Eugene Wescott of the University of Alaska at Fairbanks took to the skies again, this time with a color video camera. Coordinating with ground-based teams, the pair made observations from two aircraft, allowing them to accurately measure the flashes' speed, position, and altitude.

Sentman and Wescott found that the flashes fall into two categories. "Sprites" appear higher in the atmosphere, some 75 to 85 km above ground, and last for a few thousandths of a second. Though they don't connect to the storm clouds, some of these blood-red flashes have dangling blue tendrils.

In contrast, says Wescott, "jets" last longer, originate at the tops of storm clouds, and shoot up to an altitude less than half that of sprites. Jets are narrower than sprites, fanning out like a trumpet in a blue or purple hue.

Wescott speculates that the electric field generated by lightning travels up through the atmosphere and then discharges, creating the sprites. But the jets, although also associated with thunderstorms, appear to be "a completely new phenomenon," he adds.

Daniel N. Holden of the Los Alamos (N.M.) National Laboratory and his colleagues have now linked some 300 unusual radio bursts detected by the ALEXIS satellite to possible thunderstorm activity (SN: 2/12/94, p.100).

Holden says it's tempting to associate these bursts with those seen in visible light, as well as the atmospheric gamma-ray flashes recorded by the Compton Gamma Ray Observatory But he cautions that the much shorter duration of the radio bursts suggests that they may come from a far smaller source in the atmosphere.