St. Elmo's Fire

St. Elmo's Fire on 767 Windscreen

Flying Through Iraq Thunderstorm

St. Elmo's fire is an electrical weather phenomenon in which luminous plasma is created by a coronal discharge originating from a grounded object in an atmospheric electric field (such as those generated by thunderstorms or thunderstorms created by a volcanic explosion).

St. Elmo's fire is named after St. Erasmus of Formiae (also called St. Elmo), the patron saint of sailors. The phenomenon sometimes appeared on ships at sea during thunderstorms, and was regarded by sailors with superstitious awe, accounting for the name. Alternatively, Peter Gonzalez is said to be the St. Elmo after whom St. Elmo's fire has its name.

Ball lightning is often erroneously identified as St. Elmo's fire. They are separate and distinct meteorological phenomena

Although referred to as "fire", St. Elmo's fire is, in fact, plasma. The electric field around the object in question causes ionization of the air molecules, producing a faint glow easily visible in low-light conditions. Approximately 1,000 - 30,000 volts per centimetre is required to induce St. Elmo's fire; however, this number is greatly dependent on the geometry of the object in question. Sharp points tend to require lower voltage levels to produce the same result because electric fields are more concentrated in areas of high curvature, thus discharges are more intense at the end of pointed objects.

St. Elmo's fire and normal sparks both can appear when high electrical voltage affects a gas. St. Elmo's fire is seen during thunderstorms when the ground below the storm is electrically charged, and there is high voltage in the air between the cloud and the ground. The voltage tears apart the air molecules and the gas begins to glow.

The nitrogen and oxygen in the earth's atmosphere causes St. Elmo's fire to fluoresce with blue or violet light; this is similar to the mechanism that causes neon lights to glow.

Source:
1. Wikipedia
2. Youtube

Term got from: Aircrash Investigation, Discovery Channel

Posted: How Ruey