Like their fictional namesakes, real sprites can be fickle and hard to catch. The bursts of light start more than 80 kilometres above the ground and shoot upwards from the clouds. And although they can tower up to 48 kilometres in height, they last for just a few milliseconds. This all means the lights are tough to spot from the ground – for years airline pilots were the only people to report sprite sightings.
To get a better look, Jason Ahrns at the University of Alaska-Fairbanks and colleagues took multiple flights in a Gulfstream V research plane armed with a digital camera and a high-speed video camera. The digital camera was set to take photos constantly, and about one picture in 1000 caught a sprite. The image above was snapped on 12 August in the skies over Red Willow County, Nebraska. Powerful, long-lasting thunderstorms make the US Midwest an ideal place for sprite-hunting, says Ahrns.
The team hopes to use the images and video to figure out which physical and chemical processes spark a sprite. Red sprites, for instance, probably get their deep hue from nitrogen molecules in the air, and they may affect nitric oxide concentrations in the upper atmosphere. Scientists also want to find out what gives the lights their characteristic shapes – sprites come in several varieties, including columns, carrots and jellyfish.