Watching a summer lightning storm from your porch can be a thrill, but above the thunder clouds, mostly out of sight, a show of Olympic proportions sometimes takes place: Gigantic tongues of red licking as high as 90 kilometers into the ionosphere before disappearing an instant later. Discovered only 10 years ago by physicists testing a low-light video camera from an observatory, the eerie red sprites, streaks of light called blue jets, and related phenomena are now being studied intensely to figure out their role in the planet's electrical circuitry.
Find out more at this University of Alaska, Fairbanks, site, which offers background, links to magazine articles, a bibliography, and images, including the first color photo of a sprite taken on 4 July 1994 (no, it was not an errant firework).
In the vernacular of physics, the phenomena are described as "upper atmospheric flashes excited by thunderstorms"; but the Fairbanks researchers decided on the more lyrical term "sprites" "over pie and coffee one winter evening" in 1993, says the site, which also has a form for reporting sprite sightings.
From the team's main page you can leap to info about the Sprites '99 Field Campaign, which sent a balloon above the Midwest in August to capture sprites on video. This collaborators' site offers photos from last summer as well as an essay that offers instructions for how--if you live in the high plains--you can look for sprites from your back porch.