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Ball Lightning

The phenomenon of ball lightning remains a puzzle, but a New Zealand researcher believes his theory, involving a bubble-like vortex of natural gas, could explain many of the unusual observations made of ball lightning. Lincoln researcher Peter Coleman recently presented a paper outlining his hypothesis at the 4th International Conference on Ball Lightning, held in Britain.

As its name suggests, ball lightning has traditionally been associated with lightning, although this is not always the case and there are instances of fair-weather fireballs. The usual scenario involves a glowing ball of light around 10-20 cm in diameter, which in some cases can move against the prevailing wind or exhibit unusual trajectories. Ball lightning both smaller and larger than this has been reported, including fireballs over a metre in diameter.

While numerous observations have been documented, no definitive explanation of the phenomenon has been accepted by scientists since the first formal investigation said to have been undertaken by Arago of the French Academy of Sciences in 1838.

Over the years several hypotheses have been suggested. Prominent Russian scientist Dr Peter Kapitza put forward a microwave theory, where microwaves are created by lightning and focussed onto a region which forms a plasma. One significant weakness appears to be that microwave intensities, as measured under natural conditions, are insufficient to generate such a plasma ball.

Coleman suggests that ball lightning involves the combustion of a fuel gas, such as natural gas, within a naturally occurring atmospheric vortex. The vortex must be in a transition state known as vortex breakdown, where a sudden reduction in the speed of a vortex core results in a radial expansion, often forming a bubble-like shape.

This model has the ability to explain several observations reported in the field, especially those to do with size, shape and motion. One particularly intriguing observation of ball lightning is the splitting up of a single ball into several balls which then recombine. Such a phenomenon is consistent with a known vortex phenomenon called "vortex splitting."

Experimental support for the concept has come from a demonstration of the combustion of a fuel gas (butane) inside a steel vortex chamber. A moving flame was seen to "dance" inside the chamber under the appropriate conditions required for vortex breakdown.

This new explanation of ball lightning also seems to be able to account for several claimed sightings of unidentified flying objects. Ball lightning has previously been used to explain UFOs, but proponents of the theory had to rely on inadequate ball lightning models. Aviation expert and UFO researcher Dr Phillip Klass advanced a theory which relied on corona created by high tension lines. However, any such object would necessarily have to keep in close proximity to high tension wires. However the vortex burner ball lightning hypothesis is much more able to account for the diverse shape, size and behaviour of alleged UFOs because atmospheric vortices can have a wide range of characteristics.

In one incident described as a UFO report, observers on board an aircraft flying at around 4,000 metres spotted a fireball "shaped like a basketball", which split into two to produce a small ball above and a bean-shaped one below. Passengers saw that one of the objects was spinning at high speed, and was surrounded by a green ring of light. The two objects gradually coalesced into one, and the surrounding green light ring remained. It eventually got smaller and smaller and disappeared.

Coleman says that this report is consistent with the vortex theory.

"Two forms of behaviour point to this. Firstly the high-speed spinning; secondly the splitting of one single object into [two] is explained by the phenomenon of multiple vortex breakdown. The coalescing is also characteristic of vortex breakdown behaviour."

Coleman says that he has been able to reproduce this effect in the lab.