Lightning generated during storms has been deflected for the first time in the world by pointing a laser into the sky. The technology has been successfully tested on the telecommunications tower on Mount Säntis, at an altitude of 2,500 meters in north-eastern Switzerland, which naturally receives around 100 lightning strikes per year.
The objective of the research, led by scientists from France and Switzerland, is to improve the protection of airports and space bases, among other infrastructures.
It has been tested in the communications tower on Mount Säntis, where about a hundred lightning strikes per year
Although conventional lightning rods that have been in use since the 18th century are highly effective, “damage caused by lightning costs billions of dollars each year,” say the authors of the research in Nature Photonics, where they present their results today. It is estimated that in the world as a whole there are between 40 and 120 lightning strikes per second -including those that occur between clouds and do not reach the ground-.
Unlike a classic lightning rod, which is limited to guiding the electrical current of the lightning bolts towards the ground, the laser lightning rod allows lightning to be triggered and better controlled, the researchers have found.
It was “a bit of a crazy idea,” acknowledges Aurélien Houard, first author of the research, from the Polytechnic School in Paris, in a video explaining the work.
The idea is based on taking advantage of the fact that, in high-power laser light beams, air filaments containing free electrons are formed. These electrons have been separated from the atoms in which they were trapped, thus forming ionized air (or plasma). Containing ionized air, the filaments are good electrical conductors that provide a point of attraction for electrical discharges from storms.
The objective is to improve the protection of infrastructures such as airports and space bases
This idea was first proposed theoretically in 1974 and has since been explored experimentally in laboratories. The Mount Säntis project in Switzerland was put into practice in the summer of 2021 over ten weeks in which 16 lightning strikes were recorded on the communications tower.
The researchers built the laser light source at the base of the 124-meter-tall tower. The laser beams were directed high up to pass the top of the tower, modulating so that the first filaments of ionized air were positioned a little higher. The design of the installation allows controlling the production of electrically conductive filaments up to more than one kilometer of altitude.
The results, presented now, show that the laser allows lightning to be guided from storm clouds to a conventional lightning rod located on top of the communications tower. Photos taken during a storm in which the sky was relatively clear confirmed that the path of lightning followed the straight line of the laser light beam, where the filaments of ionized air that guided the discharge were.
“This application of laser filaments had been suggested decades ago but it had never been demonstrated in a practical case as clearly as in this research,” says Lluís Torner, director of the Institut de Ciències Fotòniques (ICFO) in Castelldefels, who has not participated in the research.
For now the technology is experimental and not ready to be applied on a large scale. “These preliminary results should be confirmed in additional campaigns,” they warn in Nature Photonics the authors of the research, which has been co-led by the Polytechnic School in Paris and the University of Geneva. But they conclude that “this work represents an important step forward in the development of laser-based lightning protection for airports, launch towers or large infrastructures.”