Hunting Sky Sprites

One of the things I love about Alaska is that you can still be a pioneer up here. Lots of things haven't been explored yet, especially scientifically. Sometimes you just have to know where to look. Like up.

Two UAF scientists, Davis Sentman and Eugene Wescott of the Geophysical Institute, recently found such a place--the middle atmosphere, the thin air from about 15 to 50 miles above the earth. Jokingly called the ignorosphere, the region hasn't been combed over for purely practical reasons; our machines don't function well there. Research balloons and aircraft can't go high enough; satellites can't fly that low.

Rarely seen brilliant flashes that blast upward from the tops of thunderstorm clouds during lightning strikes have been one of the puzzles of the middle atmosphere. Until now, the flashes probably escaped serious study because of our human tendency to dismiss that which we cannot explain, especially that which flits across our brain for only 1/30th of a second. Sentman became interested in the flashes after watching a University of Minnesota scientist's black-and-white video of the phenomenon. A Space Shuttle video camera also inadvertently captured a flash, and Sentman watched that tape, too. He shared his curiosity about the flashes with Wescott, who pointed out to Sentman that they already had the tools to dig a bit deeper into the mystery.

Armed with an all-sky camera used previously for auroral research, the pair were soon winging their way to the lower 48 in the height of thunderstorm season in July 1993. Flying in a NASA DC-8 at about 40,000 feet near storms over Kansas, Iowa, and Nebraska one night, they captured 19 of the flashes on black-and-white film. The mission was so successful they went back in the summer of 1994 to capture more flashes over storms ranging from New Mexico to Florida. This time, they used two jet aircraft for triangulation so they could accurately measure the position and altitude of the flashes and an improved low-light-level TV camera. The new equipment aided their pioneering discovery.

They became the first to capture two distinct phenomena on color video--mushroom-shaped flashes of vivid red light that jumped up to 55 miles from the tops of storm clouds, and blue flashes that exploded upward from the clouds like colossal whale spouts. They also recorded what might be a radio-frequency voice of the flashes, a sharp pop that sounds like a diver entering the water with a tight splash.

With such discoveries came the pleasant responsibility of naming what they'd seen.

Sentman chose the name "sprites" for the red flashes because of their fleeting nature. He was eating dinner with a friend just after witnessing the sprites, and he told her he didn't like what they were called at the time, "cloud to ionosphere discharges, " because he thought it might be inaccurate. Sentman and his friend sought the dictionary, where they encountered the word "sprite," which is defined as a woodland elf that can be seen only out of the corner of your eye. Perfect.

Wescott and Sentman decided to name the other flashes "blue jets" after "whizzers" and "zingers" didn't make the cut. The dictionary is suddenly two phrases fatter, and the pair are flash pioneers. What that means, they aren't sure.

If red sprites and blue jets are forms of electrical discharge, they may be a danger to high-flying aircraft. Even if they're not, the flashes have caught the eye of the media. Photos of red sprites and blue jets taken from Sentman and Wescott's project have appeared in magazines around the world, from Aviation Week to the London Times.

NASA recently funded further study of the flashes for Sentman and Wescott in South America this February. They want to explore the skies over the Amazon Basin, which Wescott called the thunderstorm capitol of the world.

"The earth is a pretty picked-over place," Sentman said. "Thousands of scientists have been crawling over it for years, and there's not a whole lot left unstudied. Oddly enough, this escaped detection up till now."

Spoken like a true pioneer.

Pictures and further explanations of these phenomena can be found on the
Red Sprites and Blue Jets page.