On June 20th, a thunderstorm in Austria unleashed a spectacular display of lightning. Observers on the ground witnessed blinding flashes of crackling light. The most amazing aspect of the outburst, however, was to be found high above the clouds. 80 km high, to be exact, in the realm of the sprites:
Red sprites
© Martin Popek
Martin Popek photographed the display from his private observatory in Nýdek, Czechia, more than 500 km away from the storm. Such distances are ideal for seeing above the tops of towering thunderclouds:
How to look for sprites
© Space Weather
"Jellyfish sprite events like these are produced by very impulsive cloud-to-ground lightning flashes draining positive charge from the stratiform rain region in large thunderstorms," explains lightning scientist Oscar van der Velde of the Technical University of Catalonia, Spain. Somehow, in a process that researchers only partially understand, the resulting electric fields draw jellyfish forms out of the cloudtops.

The tops of the sprites were surrounded by a saucer-like halo of red light, notes van der Velde. "The halo is evidence of intense electric fields at 80-90 km shaking up the electrons (colliding with nitrogen to produce light) for such a short time that sprite streamers cannot form. At lower altitudes the field exists longer, allowing the jellyfish sprite streamers to grow from electron avalanches."

Although sprites have been seen for at least a century, most scientists did not believe they existed until after 1989 when sprites were photographed by cameras onboard the space shuttle. Now "sprite chasers" routinely photograph sprites from their own homes. "I used up a Watec 910HX security camera with UFOCapture software to catch my sprites," says Popek. Give it a try!