Carrots over Nebraska

Discover, January 31, 1995

Walter Lyons says he saw the Angel of Death last summer. It towered over a nighttime Nebraska thunderstorm, its head reaching 50 miles into the sky, its wings extending out into the stratospheric darkness. Then, after a few hundredths of a second, it disappeared.

Lyons isn’t given to mystical hallucinations. He’s an atmospheric scientist at Mission Research Corporation in Fort Collins, Colorado, and he has a contract from NASA to look for enigmatic flashes of light. Lyons and his co-workers have found hundreds of them, and they sometimes give names to the wild shapes. “We’ve got the Angel of Death, we’ve got one called the Bird, one called the Blessed Trinity,” Lyons says. “And then we’ve got the Dancing Carrots.”

For a century people have claimed to see strange bursts of light above thunderstorms, but it wasn’t until the late 1980s that scientists captured a few of them on low-light-adapted video cameras. And it wasn’t until 1994 that it became clear how alive the stratosphere is with electromagnetic activity–visible light bursts like the ones Lyons has seen as well as a steady fusillade of radio waves and gamma rays. “For several years we thought it was a totally rare, fluke event,” says Lyons. No one thinks that anymore.

In 1993, Lyons set up a video camera 12 miles northeast of Fort Collins on Yucca Ridge, where he could get an unobstructed view hundreds of miles east over the Great Plains. That summer his camera captured more than 600 optical flashes; last summer he captured hundreds more. They come in colors such as orange and salmon, and they extend as far as 50 miles above the cloud tops and a dozen or so miles across. Unlike a simple lightning bolt or a curtainlike aurora, these flashes have complicated three-dimensional structures consisting of columns, spikes, blobs, and tendrils.

Meanwhile other researchers have been detecting strange flashes at other wavelengths, with sensors that were never designed for the purpose. A Department of Energy satellite named ALEXIS went into orbit in 1993 to detect the bursts of radio waves released during nuclear explosions; it has registered more than 100 flashes coming from Earth’s atmosphere that have no identifiable man-made source. Normal lightning releases radio waves, but these flashes are 10,000 times more powerful. In 1991 NASA launched the Compton Gamma Ray Observatory to collect gamma rays, the most energetic type of electromagnetic radiation, from black holes and other astronomical bodies; but the satellite has been unexpectedly bombarded from the planet below by dozens of gamma ray flashes, each lasting a few milliseconds. Regular lightning bolts can’t be the source: it’s not clear whether they release gamma rays, but if they do, the rays would be absorbed by atmospheric molecules long before they reached the satellite. Researchers can only assume that the gamma rays originate in the stratosphere, where the air is thin enough for them to escape.

But how the gamma rays or any of the other weird flashes are produced is still anyone’s guess. The only clue is that they all seem to come from the vicinity of thunderstorms. The tops of clouds may become so charged that they create upside-down “superbolts” of lightning that race up through the stratosphere. Or the clouds may create electric fields of such strength and size that they ionize huge volumes of air and make them glow like fluorescent lightbulbs. Or both these things may happen. “All we know for now,” says Lyons, “is that the more we look above thunderstorms, the weirder it gets.”