On June 8, 2016, amateur astronomer Thomas Ashcraft captured an enormous ring of light high above a thunderstorm in southeast Colorado.
"It only lasted about a millisecond, but it was definitely there. The ring was about 300 km (186 miles) wide," Ashcraft estimates.
He photographed the phenomenon using a low-light video camera:
This is an example of an ELVES (Emissions of Light and Very Low Frequency Perturbations due to Electromagnetic Pulse Sources), SpaceWeather's Dr. Tony Phillips explains.
This phenomenon appears when a pulse of electromagnetic radiation from lightning propagates up toward space and hits the base of Earth's ionosphere. A faint ring of light marks the broad 'spot' where the EMP hits.
ELVES often appear alongside red sprites. Indeed, Ashcraft's camera caught a cluster of sprites leaping straight up through the middle of the donut. "Play the complete video to see the sprites," says Ashcraft.
The one millisecond lifetime of this phenomenon explains why ELVES are so elusive and invisible to the human eye.
They were first seen in a video recorded by cameras on the space shuttle on October 7, 1990, directly above an active thunderstorm off the coast of French Guyana (Boeck et al., 1992):
"A large horizontal flash appeared at the altitude of the airglow layer. It occurred in the video field before the appearance of main lightning flash in a thunderstorm that was near the limb of the Earth. They [Boeck et al.] concluded that the causative lightning flash occurred slightly after the video scan passed the location of the storm image. There was a clear view of the mesosphere below the airglow layer, but there was no indication of a sprite in the video sequence (although a sprite event was captured 4½ hours earlier under similar moonlight conditions). The video was presented at the 1991 Spring AGU meeting (Boeck et al., 1991a) as well as at the Aerospace Lightning Conference (Boeck et al., 1991b).
Several years passed before there was a second successful measurement of the ELVES phenomenon. On June 23, 1995 Lyons et al. (1995) and Fukunishi et al. (1996) confirmed the existence of a flash similar to the airglow flash seen earlier in the shuttle data, and Lyons et al. (1995) gave it the name Emissions of Light and Very Low Frequency Perturbations From Electromagnetic Pulse Sources (ELVES). Lyons presented video images captured by a low-light-level TV camera sited near Ft. Collins, Colorado."
- "The Role of the Space Shuttle Videotapes in the Discovery of Sprites, Jets, and Elves" - Boeck et al. - GHRC
Featured image: ELVE captured by Thomas Ashcraft above Colorado, US on June 8, 2016. Credit: Thomas Ashcraft