Red sprites are poorly-understood atmospheric phenomena. They are bright glowing shapes that temporarily appear above the clouds. The Florida Institute of Technology has captured high-speed video of a sprite in action.
Above is a picture of a red sprite taken from the International Space Station. The sprite is the faint smudge of red directly above the bright white-violet glow. Their relative dimness and their extreme rarity meant that sprites weren’t physically discovered until 1989, and seem to be caused by cloud-to-ground lightning strikes.
Scientists at the Florida Institute of Technology believe that lightning strikes to the ground cause sprites because they cause atmospheric gravity waves—which are atmospheric waves similar to waves created by a rock being dropped into a pond. The bigger the waves, the more likely they are to create sprites.
Two high-sensitivity cameras on two airplanes take a look at sprite formation, and seem to confirm that hypothesis. They also captured very rare footage of a forming sprite. Have a look!