Israeli scientists have created ball lightning in their laboratory. Joe Banks and I once tried (unsuccessfully) to create it in a household microwave oven, but that's another story...

<em>Great balls of lightning</em>

If you have ever seen a mysterious ball of lightning chasing a cow or flying through your window during a thunderstorm, take comfort from the fact that you have witnessed a very rare phenomenon. Indeed, ball lightning -- a slow-moving ball of light that is occasionally seen at ground level during storms -- has puzzled scientists for centuries. Now, however, researchers in Israel have built a system that can create lightning balls in the lab. The work may not only help us to understand ball lightning but could even lead to practical applications that make use of these artificial balls (Phys. Rev. Lett. 96 045002).

Ball lightning is thought to be a ball of plasma that is formed when a bolt of lightning hits the ground and creates a molten "hot spot". The ball can typically measure 30 centimetres across and can last for a few seconds. Although they are generally created during thunderstorms, Eli Jerby and Vladimir Dikhtyar from Tel Aviv University in Israel have now been able to make lightning balls in the lab using a "microwave drill".

The device consists of the magnetron from a 600-watt domestic microwave oven and concentrates its power into a volume of just one cubic centimetre. The researchers inject the microwaves though a pointed rod into a solid substrate made from glass, silicon, germanium, alumina or other ceramics. The energy from the microwaves then produces a molten hot spot in the substrate.

What the scientists then do is pull the microwave drill out of the solid, which drags the molten hot spot and creates a hot drop. The drop then becomes a floating fireball that measures about 3 centimetres across and lasts for some tens of milliseconds (see figure). "The fireball looks like a hot jellyfish, quivering and buoyant in the air," says Jerby.

More over at <a href="http://physicsweb.org/articles/news/10/2/6/1" target="new" >Physics Web</a>