‘Dressed’ Double Laser May Give Scientists the Ability to Trigger Lightning and Rain
Researchers at the University of Central Florida's College of Optics & Photonics and the University of Arizona have created a new and innovative approach to emit a high-energy laser beam into clouds to make it rain or trigger lightning.
Due to lightning and water condensation's connection in statically-charged clouds, if scientists could stimulate thunderstorm particles with an effective laser, then they could make it rain on demand. A report on the project's status, "Externally refueled optical filaments," was recently published in Nature Photonics.
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Scientists have already developed the technology to send lasers long distances, but "when a laser beam becomes intense enough, it behaves differently than usual — it collapses inward on itself," said Matthew Mills, a graduate student in the Center for Research and Education in Optics and Lasers (CREOL). "The collapse becomes so intense that electrons in the air's oxygen and nitrogen are ripped off creating plasma — basically a soup of electrons."
The collapse from oxygen exposure is known as filamentation, which is what led the team of researchers to try and protect it with a cylinder-like method.
"What would be nice is to have a sneaky way which allows us to produce an arbitrary long 'filament extension cable.' It turns out that if you wrap a large, low intensity, doughnut-like 'dress' beam around the filament and slowly move it inward, you can provide this arbitrary extension," Mills said. "Since we have control over the length of a filament with our method, one could seed the conditions needed for a rainstorm from afar. Ultimately, you could artificially control the rain and lightning over a large expanse with such ideas."
In the past, researchers have been able to cause "electrical events" in the clouds, but they've never been able to achieve the ability to create lightning strikes. Although, almost exactly six years ago at the top of 10,500-foot South Baldy Peak in New Mexico, a team of European scientists were able to trigger electrical discharges into thunderclouds with a laser light.
"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 plasma filaments created by the laser beam were able to conduct electricity comparable to Benjamin Franklin's kite string, except there was no air-to-ground connection made. Kasparian said if they could figure out how to create longer living filaments, they could use the laser to conduct lightning during storms.
The concept of using lasers to trigger lightning strikes was proposed more than 30 years ago, however the available technology couldn't generate a long enough channel of plasma energy. Pulsed lasers have the ability to form large enough plasma filaments to act as a wire conductor shot into the clouds.
In the 1970s, small rockets attached to spools of long wires were used to trigger lightning strikes. This method was only successful 50 percent of the time and required many hours of attempts. Laser technology would give scientists the luxury of a quicker, cost-effective, and efficient process to control rain and trigger lightning.
"Because a filament creates excited electrons in its wake as it moves, it artificially seeds the conditions necessary for rain and lightning to occur," Mills said.
This would be a great achievement in weather control and prediction. Mills and his fellow graduate student researchers have been able to extend the pulse from 10 inches to now seven feet with plans to increase the distance.
"This work could ultimately lead to ultra-long optically induced filaments or plasma channels that are otherwise impossible to establish under normal conditions," said professor Demetrios Christodoulides, who is working with the graduate students on the project.
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