Ever since I learned about sprites, the bizarre electric discharges associated with thunderstorms that shoot up in the sky instead of down to the ground, I’ve wanted to see one. July’s a great month to be on the look out for these short-lived red flashes that come and go in milliseconds. They occur some 50 miles above active thunderstorms – about the same level as noctilucent clouds – and extend upward from 12 to 19 miles. The name refers to the phenomenon’s spooky, elusive nature like the folkloric fairies of old.
Dr. Dave Sentman of the University of Alaska, Fairbanks is one among a small group of researchers who have been studying these mysterious bursts of colored light. Although no one’s sure what sprites really are or what causes them, these scientists have learned that sprites contain a great deal of energy.
They’re associated with positive cloud-to-ground lightning discharges but unlike lightning, they direct their energy toward outer space into Earth’s ionosphere. In addition to light, sprites also radiate radio waves and even pulses of high-energy gamma rays.
Sentman and other scientists flew above thunderclouds to study sprites up close. Seen nearly head-on, he describes them as colorless and about as bright as the aurora; younger members of the team with younger eyes spied the red color.
Sprites aren’t the only recently discovered electrical discharge to pop up in thunderstorms. Similar phenomena called elves, blue jets and halos have also been recorded, though sprites are more common and likely to be observed.
So how do you see one? Well, you could get lucky and find yourself in an airplane flying between storm clouds at 35,000 feet on a cross-country vacation. If so, turn off the overhead light and squeeze your face up against the window with your eyes on the stars above.
For ground viewing, you’ll need a night-time thunderstorm but not one that covers the sky and blocks the sprites from view. Best is a clear, starry sky with a line of thunderstorms crackling away along a distant horizon. That way you have a line of sight view across the cloud tops. The next time you notice flashes of lightning in an otherwise cloudless night sky, see what direction they’re coming from and drive to where you have an open view of that horizon.
To improve your chances, avoid observing during twilight and in bright moonlight. You need dark skies and dark-adapted eyes. Fix your gaze a short distance above the line of thunderclouds while ignoring the bright flashes of lightning.
You can use a piece of cardboard or the roof of your car to help block the storm if it’s too much of a distraction.
Not all thunderstorms produce sprites, elves and the rest, so you’ll need patience to see one. The more you’re out under the stars, the better your chances.