"Sprites are a true space weather phenomenon," says lightning scientist Oscar van der Velde of the Technical University of Catalonia, Spain. "They develop in mid-air around 80 km altitude (the same altitude as noctilucent clouds and meteors). This happens when a fierce lightning bolt draws lots of charge from a cloud near Earth's surface. Electric fields [shoot] to the top of Earth's atmosphere--and the result is a sprite. The entire process takes about 20 milliseconds." Some researchers believe that cosmic rays play a role, too: subatomic particles from deep space strike the top of Earth's atmosphere, providing the "spark" that ignites this strange form of upward lightning.
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 station.
Petr Horálek of Ustupky, Czech Republic, photographed these specimens on July 6th