n May 23rd, an enormous swarm of sprites flickered and danced across the top of a thunderstorm in Oklahoma. Almost 400 miles away in New Mexico, amateur astronomer Thomas Ashcraft trained his cameras on the display. He captured the sprites--and something more:
"Note the dendritic upward spray in the midst of the sprite cluster," points out Ashcraft. "That is a possible 'pop-through gigantic jet'--a rare event."
Ashcraft has posted a video of the event (watch video below) with VLF-ELF radio emissions he recorded as a soundtrack. Turn up the volume: "The deep bass sound of the lightning stroke sounds like a distant shotgun blast in the night," he says.
What is a pop-through gigantic jet? Lightning scientist Oscar van der Velde of the Technical University of Catalonia explains: "A cluster of sprites can actually warp Earth's ionosphere, bringing it down from its usual altitude of 90 km to only 40 km." This sets the stage for the jet.
"The sprite cluster triggers an upward-directed discharge which in the past received fancy names as 'troll' or 'palm tree'," says van der Velde. "A satellite-based study by Taiwanese researchers in 2012 found them similar to gigantic jets--large isolated discharges reaching from the thundercloud toward the ionosphere. In case of a 'pop-through gigantic jet,' the lowering of the ionosphere is not uniform and the jet may then reach higher than the bottom tendrils of the sprite."
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--and more!--from their own homes. "They are easily detected by certain cameras," says van der Velde, "and if a storm is in the mood, you may record one every few minutes." Give it a try!