Severe weather conditions, like thunder and lightning storms, are constant reminders to us of the powerful and sometimes unpredictable forces of nature. A team of French and German scientists are helping to shed light on these weather elements. For the first time, they have actively triggered electrical activity in a thunderstorm. The findings are published in the journal Optics Express.
|The researchers aimed high-power pulses of laser light into a thunderstorm, which generated electrically-conductive plasma filaments|
© J. Kasparian / Téramobile/Lasim
Near the summit of the 10 783 foot high South Baldy Peak in New Mexico lies the Langmuir Laboratory for Atmospheric Research. Since it was established in 1963, the laboratory has been making use of its unique location, where thunderstorms are isolated, stationary, and relatively small, to conduct pioneering research into these meteorological phenomena.
It is here that a team of French and German scientists deliberately triggered electrical activity in thunderclouds for the first time. This unique feat was accomplished by aiming high-power pulses of laser light into a thunderstorm, which generated electrically-conductive plasma filaments.
Triggering lightning is an important tool for basic and applied research because it enables researchers to study the mechanisms underlying lightning and how it strikes. Moreover, triggered lightning allows engineers to evaluate and test the lightning-sensitivity of aeroplanes and critical infrastructure such as power lines.
'This was an important first step toward triggering lightning strikes with laser beams,' says Dr Jérôme Kasparian of the University of Lyon in France, who conducted the experiment. 'It was the first time we generated lightning precursors in a thundercloud.'
Dr Kasparian is just one of the scientists working on the Teramobile project, an international initiative led by French National Centre for Scientific Research (CNRS) in France and the German Research Foundation (DFG). Together they have built a powerful mobile laser capable of generating long plasma channels.
During the tests in New Mexico, 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 and generated small local discharges within the plasma channels.
There were, however, some limitations to the experiment. For instance, the researchers were unable to 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 metres 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.
Lightning strikes have long been the subject of scientific investigation, but despite these efforts they are still shrouded in mystery. Although 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, typically only 50% of these launches actually trigger a strike. The researchers believe that the use of laser technology will make the process quicker, more efficient and cost-effective and will pave the way for the development of a number of new applications.
The Optical Society