High-energy laser beam shot into clouds could make rain, lightning happen at will

Researchers at the University of Central Florida's College of Optics and Photonics and the University of Arizona plan to develop a new technique which will aim a high-energy laser beam into clouds to make it rain or trigger lightning.

They plan to surround the beam with a second beam to act as an energy reservoir, sustaining the central beam to greater distances than previously possible.

The secondary "dress" beam refuels and helps prevent the dissipation of the high-intensity primary beam, which on its own would break down quickly.

Water condensation and lightning activity in clouds are linked to large amounts of static charged particles. Stimulating those particles with the right kind of laser holds the key to possibly one day summoning a shower when and where it is needed.

Lasers can already travel great distances but "when a laser beam becomes intense enough, it behaves differently than usual - it collapses inward on itself," Matthew Mills, a graduate student in the Center for Research and Education in Optics and Lasers (CREOL) said.

"The collapse becomes so intense that electrons in the air's oxygen and nitrogen are ripped off creating plasma - basically a soup of electrons," he said.

At that point, the plasma immediately tries to spread the beam back out, causing a struggle between the spreading and collapsing of an ultra-short laser pulse. This struggle is called filamentation, and creates a filament or "light string" that only propagates for a while until the properties of air make the beam disperse.

"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.

A report on the project, "Externally refueled optical filaments," was recently published in Nature Photonics.