This is the first real demonstration of technology that can improve lightning protection.
Like Thor’s high-tech hammer, a powerful laser can catch lightning and change its path in the sky.
During the experiment on the top of the mountain such a laser tilted the lightning to the lightning rod researchers report online on January 16 in Nature Photonics . Scientists have previously used lasers to fight lightning in the lab, but this is the first demonstration that the technique works in real storms and could one day lead to better lightning protection.
Today, the most common lightning protection technology is the classic lightning rod, a metal pole one meter long, rooted in the ground. The metal’s conductivity attracts lightning that would otherwise strike nearby buildings or people, safely feeding that electricity into the ground. But the area shielded by the lightning rod is limited by the height of the lightning rod.
“If you want to protect some big infrastructure like an airport, a missile launch pad or a wind farm… then you need a lightning rod that’s a kilometer or hundreds of meters in size to be reliably protected,” says Aurelien Houar, a physicist at the Polytechnic Institute of Paris in Palaiseau, France. . Such a high metal pole will be impractical. But the laser can reach that distance by intercepting distant lightning bolts and directing them toward ground-based metal rods.
Howard and his colleagues tested this idea on top of Mount Saintis in northeastern Switzerland. They installed a powerful laser near a telecommunications tower with a lightning rod, which is struck by lightning about 100 times a year. The laser was aimed at the sky for about six hours during a thunderstorm from July to September 2021.
The laser fired short, intense bursts of infrared light at the clouds about 1,000 times per second. This train of light pulses stripped electrons from air molecules and knocked some air molecules out of their path, carving a channel through the charged, low-density plasma. Similar to clearing a path through the woods and laying a sidewalk, this combination of effects facilitated the flow of electric current along this route ( SN: 3/5/14 ). This created a path of least resistance for lightning across the sky.
Howard’s team adjusted their laser to create this conductive path just above the top of the tower. This allowed the tower’s lightning rod to intercept the laser-engaged arrow before it made its way to the laser equipment.
While the laser was working, the tower was struck by lightning four times. One of these impacts occurred in fairly clear skies, allowing two high-speed cameras to capture the moment. These images showed lightning zigzagging down from the clouds and following the laser light about 50 meters to the tower’s lightning rod.
To trace the paths of the three arrows they couldn’t see, the researchers looked at the radio waves emitted by the lightning. These radio waves showed that the three shocks followed the path of the laser much more closely than the other shocks that occurred when the laser was turned off. This implied that the laser directed those three strikes at the lightning rod as well.
“It’s a real breakthrough,” says Howard Milchberg, a physicist at the University of Maryland in College Park who was not involved in the work. “People have been trying to do this for years.” The main purpose of scientists in bending lightning at will is to improve safety, he says. But “if this thing ever becomes really, really efficient, and the probability of directing the discharge increases significantly more than it does now, it could potentially even be useful for charging.”
Atmospheric and space scientist Robert Holzworth is more circumspect about notions of application. “They showed only 50 meters [напрямної] long, and most lightning channels are kilometers long,” says Holzworth of the University of Washington in Seattle. So scaling a laser system to get useful coverage can take a lot of effort.
Using a higher-energy high-frequency laser could extend its reach, Guard said. “This is the first step towards creating a kilometer-long lightning rod.”
