July 12, 2012 — The image above, captured by Expedition 31 astronauts aboard the International Space Station (ISS) and described by NASA's Michael Carlowicz, shows an enigmatic atmospheric phenomenon known as a red sprite hovering just above a bright flash of lightning in a thunderstorm over Myanmar.
First documented in a photo in 1989, red sprites are very brief flashes of optical activity that are associated with powerful lightning discharges in storms — although the exact mechanisms that create them aren't yet known.
This image is part of a time-lapse sequence of photos captured during an ISS pass on April 30. (Watch the video here.)
Because sprites — so named because of their elusive nature — occur above thunderstorms they can be difficult to observe from the ground. For decades pilots have reported witnessing such flashes above storms but it wasn't until the '90s that they were captured clearly on camera.
Sprites typically appear as several clusters of red tendrils reaching upwards from the region of a lighting flash, sometimes extending as high as 55 miles (90 km) into the atmosphere. The brightest region of a sprite is usually around altitudes of 40-45 miles (65-75 km). Lasting only 3-10 milliseconds, sprites can appear as bright as moderate auroral activity and have been found to emit radio noise. It has even been suggested that looking for sprite activity on other planets may help identify environments that are conducive to life.
These furtive phenomena give a hint at the complex nature of Earth's electrical environment, and how storms and weather influence and interact with it. Find out more about sprite research at the University of Alaska Fairbanks site.
-- by Jason Major