Lightning on demand, drawing down a bolt of lightning for performing
scientific studies, is usually done by firing a rocket into an overhead
cloud. The rocket spools out a long wire, providing a conducting path
between the charged-up cloud and the earth below. Soon this might be
done using laser pulses.
A team of French and German scientists has performed experiments in
the lab in which a laser beam ionizes air molecules between an artificial
thunderhead (a high voltage electrode) with another electrode, the equivalent
of “earth” (a grounded electrode), several meters away.
The experiment is unique in that it can trigger megavolt discharges
across self-guided plasma filaments in air generated by laser pulses.
(Here are the potent characteristics of natural lightning: peak power
of ten megawatts, peak voltage of 100 MV, peak currents of tens of kilo-amps.)
One of the lab results is the surprising discovery that rain does not
much perturb the triggering or guiding of the discharge process.
Next the team will perform open-air lightning experiments. The aim
of this work will be to obtain the ability to trigger lightning before
it occurs naturally at sensitive sites such as airports or electrical
et al., Applied Physics Letters, 6 December 2004;
contact Jerome Kasparian, Universite Lyon, firstname.lastname@example.org