A ball-lightning-like plasma cloud is produced in an underwater discharge

Credit: D Lange IPP

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BERLIN, 7 June 2006 - Luminous balls of plasma that hover above water like ball-lightning have been generated in the lab by a group of German physicists. While they are not saying it is ball-lightning, they claim that their result will help solve the mystery of this natural phenomenon.

Ball-lightning is a luminous phenomenon that occurs during thunderstorms. It is a mystery, however, why the lightning is visible not as a brief flash, like normal lightning, but for several seconds. Ball lightning has never been reliably photographed, nor studied in the lab. However many historical figures claim to have witnessed it. Besides Pliny the Elder, Charlemagne and Henry II of England, in modern times the Nobel Prize winners in physics, Niels Bohr and Pjotr Kapitza, claim to have seen it.

"In view of this incertitude it has been variously attempted to induce the phenomenon under controlled conditions in the laboratory", said Gerd Fussmann, head of the plasma physics study group of the Max-Planck-Institut - Plasmaphysik and Berlin's Humboldt University.

Inspired by the work of some Russian researchers, the plasma physics study group produced what they described as 'plasmoids' above a water surface that had lifetimes of about 0.3 seconds and diameters of 10 to 20 centimetres.

To achieve this, they sparked a short high-voltage discharge in a water tank. When it decayed a plasma ball then emerged from the surface.

The equipment generated impressive "ball-lightning" in every possible manifestation and colour about every five minutes.

The researchers said the plasmoids were glowing, but did not appear to be hot. A sheet of paper placed on top of the ball did not catch fire.

Professor Fussmann: "Why luminous phenomena occur at all is anything but clear. They continue to be visible about 300 milliseconds after the current has decayed and the energy input is cut off. However, they should really go out after a few milliseconds at most."

Several PhD students have proposed to investigate the plasmoid further.