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article imageFirst Step Toward Manmade Lightning Taken

By Bob Ewing     Apr 14, 2008 in Science
A team of European scientists has deliberately triggered electrical activity in thunderclouds for the first time. They were able to accomplish this feat by aiming high-power pulses of laser light into a thunderstorm.
For the first time, European scientists have intentionally triggered electrical activity in thunderclouds. The experiment is published in the latest issue of Optics Express, the Optical Society’s (OSA) open-access journal. The team accomplished this by aiming high-power pulses of laser light into a thunderstorm.
The press release says that at the top of South Baldy Peak in New Mexico during two passing thunderstorms, the researchers used laser pulses to create plasma filaments that could conduct electricity akin to Benjamin Franklin's silk kite string. No air-to-ground lightning was triggered because the filaments were too short-lived, but the laser pulses generated discharges in the thunderclouds themselves.
"This was an important first step toward triggering lightning strikes with laser beams," says Jérôme Kasparian of the University of Lyon in France. "It was the first time we generated lighting precursors in a thundercloud." The next step of generating full-blown lightning strikes may come, he adds, 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.
Why trigger lightning strikes; because it 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.
Pulsed lasers represent a potentially very powerful technology for triggering lightning because they can form a large number of plasma filaments, which are ionized channels of molecules in the air, that act like conducting wires extending into the thundercloud.
This concept was first suggested more than 30 years ago. To date, 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.
Kasparian and his colleagues, who are involved in the Teramobile project which is an international program that was 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.
They tested the laser at the Langmuir Laboratory in New Mexico, which is equipped to measure atmospheric electrical discharges. This laboratory Sitting at the top of 10,500-foot South Baldy Peak, and is in an ideal location because its altitude places it close to the high thunderclouds.
The research team, during the tests, 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.
The experiment has limitations, for example, they could not generate plasma channels that lived long enough to conduct lightning all the way to the ground. The plasma channels dissipated before the lightning could travel more than a few meters along them. 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.
Scientists have been able to trigger lightning strikes since the 1970s by shooting small rockets into thunderclouds that spool long wires connected to the ground, the results ere that typically only 50 percent of rocket launches actually trigger a lightning strike. The use of laser technology would make the process quicker, more efficient and cost-effective and would be expected to open a number of new applications.
Kasparian conducted the research with his colleagues at CNRS, the University of Lyon, the University of Geneva, École Polytechnique and ENSTA in Palaiseau, France, the Free University of Berlin and the Dresden-Rossendorf Research Center as part of the Teramobile project. This work was funded jointly by the CNRS, DFG, the French and German ministries of foreign affairs, Agence Nationale de la Recherche, Fonds national suisse de la recherche scientifique, and the Swiss Secrétariat d'État à l'Éducation et à la Recherche.
couretsy flickr/SIMON/Gadget
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