Engineers Create Stable Plasma Ring in Open Air

For the first time, engineers at Caltech have created a stable ring of plasma in open air-essentially capturing lightning in a bottle, but without the bottle. Matter can exist in four distinct phases: solid, liquid, gas, and plasma. Plasmas are made of charged particles-ions and electrons-and occur naturally on Earth as lightning, in the weather phenomenon called St. Elmo's fire (in which glowing balls of light sometimes appear on pointed objects during storms) as well as and in man-made objects such as fluorescent light bulbs and plasma cutting torches. Usually, plasmas do not have clearly defined shapes of their own. Lighting follows a path of least resistance through the air, creating wildly forking structures, while man-made plasmas are constrained by vacuum chambers or electromagnetic fields. As such, Morteza (Mory) Gharib (PhD '83), the Hans W. Liepmann Professor of Aeronautics and Bioinspired Engineering at Caltech, says he was surprised when he and his team were able to generate a stable ring of plasma in open air using just a stream of water and a crystal plate. Their findings will be published in the Proceedings of the National Academy of Sciences the week of November 13.