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What causes St. Elmos fire?

As a retired advanced weather spotter for the National Weather Service in Pontiac Michigan, I have observed numerous weather phenomon. I have “ball lightning” on video.

St. Elmo’s Fire is an electrical weather phenomenon in which visible plasma is created by a coronal discharge originating from a grounded object in an atmospheric electric field (such as those generated by thunderstorms).

St. Elmo’s fire is named after Erasmus of Formiae (also called St. Elmo), the patron saint of sailors (who sometimes held its appearance to be auspicious). 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.(Wikipedia)

Physically, St. Elmo’s Fire is a bright blue or violet glow, appearing like fire in some circumstances, from tall, sharply pointed structures such as lightning rods, masts, spires and chimneys, and on aircraft wings. St. Elmo’s Fire can also appear on leaves, grass, and even at the tips of cattle horns. Often accompanying the glow is a distinct hissing or buzzing sound.

Benjamin Franklin correctly observed in 1749 that it is electric in nature.

Scientific Explanation

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 centimeter is required to induce St. Elmo’s Fire; however, this number is greatly dependant 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 object.

The nitrogen and oxygen in 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.

Flying through Iraq thunderstorm

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August 31, 2007 - Posted by | Global Health Vision, Global News, RSS, Science, St. Elmos Fire, US Army soldiers in Iraq, Weather Anomolies

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