'The St. Elmo's Fire phenomenon is essentially a naturally occurring fluorescent light.'
Plasma, an ionized gas, is the most common form of matter in the universe (as stars are made of plasma), and it is also common in consumer products (neon signs, fluorescent lamps, plasma TVs). St. Elmo's Fire, the phenomenon named by sailors for the glow with which it surrounded the masts of ships, is essentially just the result of an object discharging electricity and ionizing the air around it.