new type of sprite
© Thomas AshcraftA new type of sprite?
Barely 30 years ago, many researchers did not believe that upper atmospheric lightning existed-until 1989 when researchers from the University of Minnesota captured them on video tape. Now there is a menagerie of accepted forms: sprites, elves, gigantic jets, gnomes. These "transient luminous events" (TLEs) appear above thunderclouds, reaching toward space rather than lancing down to the ground like regular lightning.

On Aug.14th, Thomas Ashcraft may have spotted a new kind of sprite. "I was photographing a cluster of sprites over a thunderstorm in western Oklahoma when something curved snaked up behind the main cluster." This frame from his video of the event shows the strange form:

Sprite and rare Secondary Gigantic Jet - August 14 2017 from Thomas Ashcraft on Vimeo.


What was it? Experts aren't sure.

Lightning researcher Oscar van der Velde at the Technical University of Catalonia says it could be a troll-a type of TLE that sometimes appears underneath sprites, crawling up tendrils dangling beneath the luminous clusters. "I have recorded many trolls," says van der Velde, "but never such weird curving ones. This is a really exceptional display."

Jozsef Bo'r of the Geodetic and Geophysical Research Institute in Hungary thinks it might be a type of gigantic jet. Gigantic jets are like sprites on steroids-powerful and bright. "A working hypothesis is that the red sprites in the photo occurred first and deposited a cloud of positive charge above the thundercloud. A subsequent gigantic jet was itself rich in positive charge and had to bend around the positive cloud on its way up."

Or it could be something unprecedented. "Even after almost 30 years of sprite observations, we are still seeing new things," says Walter Lyons, past president of the American Meteorological Society and a longtime observer of sprites. "Over the years I have seen thousands of sprites, but only a few curved structures like this -- so this is pretty rare."

"I don't know what to call them," says Ashcraft, who regularly monitors the sky around his private observatory in New Mexico for strange phenomena, "but I am going to keep my eyes open for more."