Recently even more exotic forms of lightning have been discovered above thunderstorms. Faint flickers of light from the tops of storms had been reported for more than a century—some observers said it looked as though the tops of clouds were on fire—but verification was difficult until the right instruments were developed. In fact some Air Force pilots had seen the phenomenon for years but were reluctant to report lightning that went the “wrong” way. In 1989 researchers videotaped a pulse of light leaping from the top of a thunderstorm toward the heavens. With no idea what they were seeing, they dubbed it a sprite.
In 1994 a group of scientists from the University of Minnesota in a high-flying NASA jet were testing a low-light camera normally used to image the aurora borealis. While orbiting high over a thunderstorm, they pointed the camera at the distant horizon and quite accidentally captured the first color images of a sprite. The pictures revealed a large red puff rising from the storm, appearing just as a powerful lightning bolt exploded below. The sprite, which had a surprisingly delicate structure, rose some 60 miles toward space before dissipating.
What could account for the existence of something that looked like a huge red jellyfish high in the atmosphere? That’s still being debated, but scientists do know a few things about sprites:
• They appear only during very large thunderstorms.
• They’re usually brightest about 40 miles up in the atmosphere.
• They last only about ten milliseconds.
• They appear only after reverse, or positive, cloud-to-ground lightning.
• They almost always appear in groups.
With the discovery of sprites, many more observers turned their attention to the lofty heights of severe thunderstorms, and soon some other strange effects were discovered. Narrow beams of blue light were spotted over some clouds. Named blue jets by their discoverers, these narrow cone-shaped columns seem to leap from the top of a thunderstorm and soar high into the stratosphere at more than 300 times the speed of sound. Although they’re much rarer than sprites, blue jets are a bit more long-lived; they are visible to the naked eye at night.
Shortly after the discovery of blue jets, scientists at Stanford University announced that they had spotted an even stranger light in the heavens: a red halo that seemed to do the impossible by propagating outward from a thunderstorm to an altitude of about 40 to 60 miles high at a velocity faster than the speed of light. But it wasn’t yet time for Einstein to roll over in his grave; further research showed that no single particle was moving that fast. The phenomenon, dubbed “elves,” was caused by air molecules firing in rapid sequence after being stimulated by the lightning pulse, like chase lights around a movie marquee. Their causes are still being investigated.
One theory on the origin of elves says that the electromagnetic pulse caused by a lightning strike can rise and expand through the cloud like a balloon, finally breaking free above the storm, where it causes charged particles to glow red. Others say they could be caused by storm-produced gamma rays that were recently detected by NASA’s Compton Gamma Ray Observatory satellite.
Each year, lightning starts around 10,000 forest fires in the United States alone, laying waste to more than $50 million worth of timber. The National Lightning Safety Institute estimates that the total cost of lightning strikes, including damage to both property and people, may total upward of $4 billion to $5 billion per year. A strike near your home can shred your trees, shut off your power, and cook your appliances. A large, well-placed bolt can knock out power to an entire city.
Brownouts and blackouts can wreak havoc with your electronic devices, and a lightning strike can destroy them. A surge protector for each device is imperative, but an even better bet is an uninterruptible power supply (UPS), which can allow you to shut your computer down after a power problem without losing data.
On the night of July 13, 1977, a line of thunderstorms formed to the north of New York City. The sound of air conditioners running at full blast nearly drowned out their rumble as New Yorkers sought relief from the heat. Shortly after 8:30, powerful lightning strikes hit two high-voltage power lines, starting a chain of events that knocked out the city’s power grid and plunged the Big Apple into darkness. During what became known as the Night of Terror, 3,776 people were arrested for looting and other crimes, and the fire department fought 1,037 blazes. One Bronx dealership was robbed of fifty cars in a single evening. Thousands were trapped in darkened elevators and subway cars. Both Kennedy International and LaGuardia Airports were closed, and hospitals were forced to resort to emergency generators for power.
With so much at stake, the federal government assisted in financing a national lightning data service that eventually grew into the National Lightning Detection Network (NLDN). Consisting of a web of magnetic direction finders scattered across the country, the NLDN can instantly triangulate the location of a cloud-to-ground lightning strike and transmit that information to the Network Control Center, where it appears on an electronic map of the United States. Warnings can now be issued for storms with especially violent electrical activity.