Seeing Sprites: Researchers Catch Glimpses of Electromagnetic Bursts High in Earth’s Atmosphere |
High above the clouds during thunderstorms, some 50 miles above Earth a different kind of lightning dances. Bursts of red and blue light, known as “sprites,” flash for a scant one thousandth of a second. They are often only visible to those in flight above a storm, and happen so quickly you might not even see it unless you chance to be looking directly at it. One hard-to-reach place that gets a good view of sprites is the International Space Station. On April 30, 2012, astronauts on the ISS captured the signature red flash of a sprite, offering the world and researchers a rare opportunity to observe one.
Indeed, sprites are so hard to catch on film, that pilots had claimed to see them for almost a century before scientists at the University of Minnesota accidentally caught one on camera in July of 1989. Since then, researchers aboard planes have occasionally snapped a shot, but it continues to be difficult to methodically film them. So a group of scientists, along with help from Japan’s NHK television, sought them out regularly for two weeks in the summer of 2011.
Filming at 10,000 frames per second on two separate jets, the team recorded some of the best movies of sprites ever taken — movies that can be used to study this poorly understood phenomenon and the forces that create them. By filming from two jets flying 12 miles apart, the team mapped out the 3-dimensional nature of the sprites. Ground-based measurements rounded out the picture.
“Seeing these are spectacular,” says Hans C. Stenbaek-Nielsen, a geophysicist at the University of Alaska in Fairbanks, Alaska. “But we need the movies, because not only are they so fast that you could blink and miss them, but they emit most of their light in red, where the human eye is relatively blind.” continue reading