St. Elmo's fire

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For other uses, see St. Elmo's fire (disambiguation).
St. Elmo's Fire on a ship at sea
St. Elmo's Fire on a ship at sea

St. Elmo's fire is an electroluminescent coronal discharge caused by the ionization of the air during thunderstorms inside of a strong electric field. Although referred to as "fire", St. Elmo's fire is in fact a low density, relatively low temperature plasma caused by massive atmospheric electrical potential differences which exceed the dielectric breakdown value of air at around 3 megavolts per meter. 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.

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[edit] Observation

Physically, St. Elmo's fire is a bright pink-purple glow, appearing like fire in some circumstances, often in double or triple jets, from tall, sharply pointed structures such as masts, spires and chimneys, and on aircraft wings.

It is named such because the phenomenon commonly occurs at the mastheads of ships during thunderstorms at sea, and St. Elmo is the patron saint of sailors. Benjamin Franklin correctly observed in 1749 that it is electric in nature. It is said that St. Elmo's fire can also appear from the tips of cattle horns during a thunderstorm, or sharp objects in the middle of a tornado, but is not the same phenomenon as ball lightning, although they are possibly related. In ancient Greece, the appearance of a single one was called Helena and two were called Castor and Pollux.

[edit] See also

[edit] Other works

Image of a Lichtenberg figure like static discharge occurring on the outer surface of a glass cockpit window during flight through a strong thunderstorm. This phenomenon is commonly referred to as St. Elmo's fire by pilots, though strictly speaking, it is simply a form of static discharge. The phenomenon of St. Elmo's fire proper, that is, a diffuse corona discharge, also can very briefly be seen in the video from which this image was taken (at time 2:00 minutes). Full video:[1].
Image of a Lichtenberg figure like static discharge occurring on the outer surface of a glass cockpit window during flight through a strong thunderstorm. This phenomenon is commonly referred to as St. Elmo's fire by pilots, though strictly speaking, it is simply a form of static discharge. The phenomenon of St. Elmo's fire proper, that is, a diffuse corona discharge, also can very briefly be seen in the video from which this image was taken (at time 2:00 minutes). Full video:[1].

References to St. Elmo's fire, also known as "corposants" or "corpusants" from the Portuguese corpo santo[1] ("holy body"), can be found in the works of Julius Caesar (De Bello Africo, 47), Pliny the Elder (Naturalis Historia, book 2, par. 101) , Herman Melville, and Antonio Pigafetta's journal of his voyage with Ferdinand Magellan. St. Elmo's fire was a phenomenon described in The Lusiads.

Charles Darwin noted the effect while aboard the Beagle and wrote of the episode in a letter to J.S. Henslow that one night when the Beagle was anchored in the estuary of the Río de la Plata: "Everything was in flames, the sky with lightning, the water with luminous particles, and even the very masts were pointed with a blue flame."

There is a possible reference to St. Elmo's fire in Samuel Taylor Coleridge's The Rime of the Ancient Mariner:

About, about, in reel and rout
The death-fires danced at night;
The water, like a witch's oils,
Burnt green, and blue, and white.

Another reference made to St. Elmo's fire can be found in Ludovico Ariosto's epic poem Orlando Furioso. It is located in the 19th canto after a storm has punished the ship of Marfisa, Astolfo, Aquilant, Grifon, and others, for three straight days. "But now St. Elmo's fire appeared, which they had so longed for, it settled at the bows of a forestay, the masts and yards all being gone, and gave them hope of calmer airs."

In the comic book Tintin in Tibet by Herge, Captain Haddock's ice axe is hit by St. Elmo's fire.

Occasionally, St. Elmo's fire is associated with the Greek element of Fire, as well as with one of Paracelsus's elementals, specifically the salamander, or, alternatively, with a similar creature referred to as an acthnici [2].

Welsh mariners knew it as canwyll yr ysbryd ("spirit-candles") or canwyll yr ysbryd glân ("candles of the Holy Ghost"), or the "candles of St. David"[3]. In Russian they are "Saint Nicholas" or "Saint Peter's lights"[3]. They were also sometimes called St. Helen's or St. Hermes' Fire, perhaps through linguistic confusion.[4]

[edit] References

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[edit] External links

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