TORONTO – If you thought that sprites and elves were just mythical creatures of long ago, you’re wrong.
Though almost as elusive as their mythical namesakes, sprites and elves form high in the atmosphere above the tops of thunderclouds, sometimes reaching out into space. It is believed that they are associated specifically with lightning.
These bursts of red and blue light that flash for one-thousandth of a second and are often only visible in planes above storms, or even from the International Space Station (ISS).
Elves, huge red halos that are also as short-lived as sprites, are just as poorly understood as sprites. They are also caused by lightning.
These fleeting flashes of light have long fascinated scientists and many researchers have set out to better understand them.
Jason Ahrns, a graduate student from the University of Alaska, Fairbanks, is studying sprites. He managed to photograph several bright red sprites over Oklahoma City on Aug. 6.
Ahrns, whose is studying auroras, – the Northern Lights – became interested in sprites after getting involved with one of the researchers at the university.
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“My own advisor was supportive of me ‘expanding my horizons’ so to speak… so here I am.”
Ahrns is involved with a joint project between the University of Alaska, Fairbanks, the United States Air Force, and Fort Lewis College. The study is sponsored by the National Science Foundation.
The main goal is to capture high-speed spectra of the sprites. Once the sprites are captured on film – at incredible speeds – researchers will study the composition of the light.
“We’ve noticed…the colour seems to change as the sprite evolves, where it’s redder on the top, then turns bluer near the bottom. You can somewhat see that in my pictures but it’s very subtle,” said Ahrns.
Capturing the sprites is no easy task. A plane, which flies out from an airport near Boulder, CO., is specially equipped to photograph the sprites. High-speed cameras are mounted on the windows on aluminum racks, along with a swivel mount so the researchers can reposition the cameras. One of the windows was even replaced with a quartz window because quartz is considered to be purer.
“We fly about 200km off the side of the storm with the high-speed cameras running and wait to see a sprite in the ‘spotter’ camera,” Ahrns said. “When I see one, I hit the trigger and it gets recorded to high speed.”
In order to determine what the sprites are comprised of, the researchers must separate the different beams of light. They do this by using something called diffraction grating.
“We’ve got a diffraction grating in front of one of the high-speed cameras which will break the light apart into its components, like that old Pink Floyd album with the prism, so we can know exactly what’s in there, and moment by moment since it will be high-speed footage,” Ahrns said. “As far as I know, that’s never been done before. We’ve recorded some spectra already, but they’re not as good as we had hoped. Still a couple of flights left, though. You basically have to get lucky.”
The study also attempts to determine which specific stroke of lightning made the sprite.
This isn’t Ahrns’ first time researching sprites. In 2011, the Japanese television station NHK sponsored a TV special where the team had cameras in two different locations in order to map the sprite in 3D nature.
Asked if he will continue with the study of sprites, Ahrns said, “I see no reason to stop anytime soon. Of course, I have to devote most of my time to auroras, or I’ll never graduate. But whenever I have the time and opportunity to work with sprites, I’m there.”
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