Washington, April 14 : Scientists have used laser pulses to deliberately trigger electrical activity in thunderclouds, which marks the first step towards manmade lightning.
According to a new paper in the latest issue of Optics Express, the experiment was conducted at the top of South Baldy Peak in New Mexico during two passing thunderstorms.
By aiming high-power pulses of laser light into a thunderstorm, the researchers created plasma filaments that could conduct electricity akin to Benjamin Franklin's silk kite string.
Though no air-to-ground lightning was triggered because the filaments were too short-lived, the laser pulses generated discharges in the thunderclouds themselves.
"This was an important first step toward triggering lightning strikes with laser beams," said Jerome Kasparian of the University of Lyon in France. "It was the first time we generated lighting precursors in a thundercloud," he added.
Kasparian and his colleagues involved in the Teramobile project, an international program initiated by National Center for Scientific Research (CNRS) in France and the German Research Foundation (DFG), built a powerful mobile laser capable of generating long plasma channels by firing ultrashort laser pulses.
During the tests, the research team quantified the electrical activity in the clouds after discharging laser pulses.
Statistical analysis showed that their laser pulses indeed enhanced the electrical activity in the thundercloud where it was aimed-in effect they generated small local discharges located at the position of the plasma channels.
Pulsed lasers represent a potentially very powerful technology for triggering lightning because they can form a large number of plasma filaments - ionized channels of molecules in the air that act like conducting wires extending into the thundercloud.
Triggering lightning strikes is an important tool for basic and applied research because it enables researchers to study the mechanisms underlying lightning strikes.
Moreover, triggered lightning strikes will allow engineers to evaluate and test the lightning-sensitivity of airplanes and critical infrastructure such as power lines.
Though the simple concept of using lasers to trigger lightning strikes was first suggested more than 30 years ago, scientists have not been able to accomplish this to date because previous lasers have not been powerful enough to generate long plasma channels.
The current generation of more powerful lasers, like the one developed by Kasparian's team, may change that.
According to Kasparian, the next step of generating full-blown lightning strikes may come, after the team reprograms their lasers to use more sophisticated pulse sequences that will make longer-lived filaments to further conduct the lightning during storms.
The team is currently looking to increase the power of the laser pulses by a factor of 10 and use bursts of pulses to generate the plasmas much more efficiently.