St Elmo’s Fire, What’s This Strange Phenomenon?

Electrostatic discharge flashes across the windscreen of a KC-10 cockpit.

St. Elmo’s fire is an electro-luminescent discharge caused by the ionization of the air during a thunderstorm, within a strong electric field. Benjamin Franklin in 1749 observed that it was an electrical phenomenon. Physically, it manifests as a brilliant, bluish-white glow, appearing in some circumstances as fire, often in double or triple jets, shooting from tall, pointed structures, such as masts, spiers…