Tuesday, July 28, 1998 Published at 12:25 GMT 13:25 UK
Chasing lights in the sky
Ghostly lights dance above thunderstorms
A team of scientists has just completed a two-week project to study mysterious lights in the upper atmosphere called red sprites and blue jets. Our science editor Dr David Whitehouse reports
Red sprites and blue jets are strange lights that appear in the upper atmosphere above thunderstorms.
The red sprites are large flashes of red light that last just a few thousandths of a second. They can reach as high as the lower edge of the stratosphere, about 90 km high.
They are faint and usually require a low light level camera to detect them.
They can spread over huge regions of the sky. Some as large as 10,000 cubic kilometres have been reported.
For two weeks a Gulfstream 2 jet aircraft has carried 8 TV imaging systems above the western United States in search of thunderstorms and sprites.
Observations in the air were co-ordinated with ground based observatories.
One remarkable event was seen over central Iowa. A sprite was seen with tendrils of light trailing all the way down to the clouds.
These dancing lights are undeniably beautiful but scientists would like to know how they are caused.
The sprites and jets indicate that thunderstorms are more complicated than was once thought. Scientists are speculating that they might be an essential part of the earth's global electrical activity.
Also in recent years there have been puzzling observations from satellites that suggest that very high energy radiation may come from thunderstorms.