Ball Lightning: Close to a Solution?
Dr. Karl Stephan
Professor, Ingram School of Engineering, Texas State University
Ball lightning has been seen by thousands of eyewitnesses, photographed, and studied by physicists such as Faraday, Oliver Lodge, the Nobelist Pyotr Kapitsa, and atmospheric scientist Bernard Vonnegut. Despite these efforts, there is as yet no theory that can completely account for its major characteristics, and no one has yet been able to reproduce it in the laboratory. Ball lightning usually takes the form of a glowing sphere between 10 and 100 cm in diameter. It is usually associated with thunderstorms, and lasts only a few seconds before it either disappears or explodes. During its lifetime its motion is erratic and mainly horizontal. Ball lightning has caused significant damage in some cases and a few reported injuries and deaths. But most instances of it are harmless and leave eyewitnesses astonished but unhurt. In a recent publication, plasma physicist H.-C. Wu has proposed a formation mechanism for ball lightning based upon high-energy lightning phenomena discovered in the last twenty years. Lightning can produce bunches of relativistic electrons with energies exceeding 1 MeV. Wu has shown that if a dense enough electron bunch collides with matter, the energy of the resulting electromagnetic pulse peaks in the microwave spectrum. If the pulse encounters a plasma, computer simulations show that a standing microwave soliton wave can form. The plasma produces a resonant microwave cavity that encloses the electromagnetic field and preserves its energy. If this plasma-walled cavity can contain kJ of energy for a time as long as seconds, this mechanism will explain many of the mysterious properties of ball lightning, including its ability to pass through closed glass windows. In this presentation we will review the history of ball lightning research, recent experimental and theoretical progress, and outline possible experimental tests that might lead to the production of ball lightning in the laboratory.