Sprites and Jets Baffle Boffins

SAN FRANCISCO--- Spectacular blood-red and blue flashes, high above the atmosphere - looking like dancing angels and trumpets - are puzzling scientists.

The luminous phenomena, called red sprites and blue jets, seem to be forms of electrical discharge.

They are accompanied by distinctive crackling and popping radio signals.

But a series of presentations yesterday at a meeting of the American Geophysical Union produced no definitive word on how they form.

Researchers used planes and ground stations to record the flashes on stormy nights above Colorado, Kansas, Nebraska and Oklahoma.

Scientists attribute the flashes, first reported in 1989, to strong negative electrical charges at the top of clouds following positively-charged lightning strikes, which release electrons into the upper atmosphere.

But the precise mechanism of their formation remains unknown.

Davis Sentman, a physics professor at the Geophysical Institute at the University of Alaska, said researchers hoped to do more observations.

"The red of sprites is probably due to oxygen. The blue jets are probably due to nitrogen," Prof. Sentman said. "But we want to know." - AP