Santelmo

St. Elmo's fire — also called Witchfire or Witch's Fire — is a weather phenomenon in which luminous plasma is created by a corona discharge from a rod-like object such as a mast, spire, chimney, or animal hornHeidorn, K.,
Weather Elements: The Fire of St. Elmo
'. Retrieved on July 2, 2007. in an atmospheric electric field. It has also been observed on the leading edges of airplanes, as in the case of British Airways Flight 009. The intensity of the effect, a blue or violet glow around the object, often accompanied by a hissing or buzzing sound, is proportional to the strength of the electric field and therefore noticeable primarily during thunderstorms or volcanic eruptions.

St. Elmo's fire is named after St. Erasmus of Formia (also known as St. Elmo), the patron saint of sailors. The phenomenon, which can warn of an imminent lightning strike, was regarded by sailors with awe and sometimes considered to be a good omen.Bergreen, Laurence. ''Over the Edge of the World: Magellan's Terrifying Circumnavigation of the Globe''. New York: Morrow, 2003. Print.

Cause

St. Elmo's fire is a reproducible and demonstrable form of plasma. The electric field around the affected object causes ionization of the air molecules, producing a faint glow easily visible in low-light conditions. Conditions that can generate St. Elmo's fire are present during thunderstorms, when high-voltage differentials are present between clouds and the ground underneath. A local electric field of about 100 kV/m is required to begin a discharge in moist air. The magnitude of the electric field depends greatly on the geometry (shape and size) of the object. Sharp points lower the necessary voltage because electric fields are more concentrated in areas of high curvature, so discharges preferentially occur and are more intense at the ends of pointed objects.

The nitrogen and oxygen in the Earth's atmosphere cause St. Elmo's fire to fluoresce with blue or violet light; this is similar to the mechanism that causes neon lights to glow, albeit at a different colour due to the different gas involved.

In 1751, Benjamin Franklin hypothesized that a pointed iron rod would light up at the tip during a lightning storm, similar in appearance to St. Elmo's fire. Quoted text from May 1751 letter published in ''Gentleman's Magazine''. Excerpt at Additional reference may be made from Yale University's collection,

Recently, experiments conducted at MIT have shown that St. Elmo's fire behaves differently in airborne objects as opposed to grounded structures.

In history and culture

*In ancient Greece, the appearance of a single instance of St. Elmo's fire was called ( grc, Ἑλένη), literally meaning "torch", with two instances referred to as Castor and Polydeuces, names of the mythological twin brothers of Helen.
*After the medieval period, St. Elmo's fire was sometimes associated with the Greek element of fire, such as with one of Paracelsus's elementals, specifically the salamander, or, alternatively, with a similar creature referred to as an acthnici.
*Welsh mariners referred to St. Elmo's fire as or ("candles of the Holy Ghost" or the "candles of St. David").
*Russian sailors also historically documented instances of St. Elmo's fire, known as "Saint Nicholas" or "Saint Peter's lights", also sometimes called St. Helen's or St. Hermes' fire, perhaps through linguistic confusion.
*St. Elmo's fire is reported to have been seen during the Siege of Constantinople by the Ottoman Empire in 1453. It was reportedly seen emitting from the top of the Hippodrome. The Byzantines attributed it to a sign that the Christian God would soon come and destroy the conquering Muslim army. According to George Sphrantzes, it disappeared just days before Constantinople fell, ending the Byzantine Empire.
*Accounts of Magellan's first circumnavigation of the globe refer to St. Elmo's fire (calling it the body of St. Anselm) being seen around the fleet's ships multiple times off the coast of South America. The sailors saw these as favorable omens.
*St Elmo's fire was seen during the 1955 Great Plains tornado outbreak in Kansas and Oklahoma.
*Among the phenomena experienced on British Airways Flight 9 on 24 June 1982 were glowing light flashes along the leading edges of the aircraft, including the wings and cockpit windscreen, which were seen by both passengers and crew. While the bright flashes of light shared similarities with St Elmo's fire, the glow experienced was from the impact of ash particles on the leading edges of the aircraft, similar to that seen by operators of sandblasting equipment.
*St. Elmo's fire was observed and its optical spectrum recorded during a University of Alaska research flight over the Amazon in 1995 to study sprites.
*Ill-fated Air France Flight 447 from Rio de Janeiro–Galeão International Airport to Paris Charles de Gaulle Airport in 2009 is understood to have experienced St. Elmo's fire 23 minutes prior to crashing into the Atlantic Ocean; however, the phenomenon was not a factor in the disaster.
*Apoy ni San Elmo – commonly shortened to Santelmo – is a bad omen or a flying spirit in Filipino folklore.

Notable observations

Classical texts

References to St. Elmo's fire can be found in the works of Julius Caesar (''De Bello Africo'', 47) and Pliny the Elder (''Naturalis Historia'', book 2, par. 101), Alcaeus frag. 34. Earlier, Xenophanes of Colophon had alluded to the phenomenon.

Zheng He

In 15th-century Ming China, Admiral Zheng He and his associates composed the Liujiagang and Changle inscriptions, the two epitaphs of the treasure voyages, where they made a reference to St. Elmo's fire as a divine omen of Tianfei (天妃), the goddess of sailors and seafarers. &

Accounts associated with Magellan and da Gama

Mention of St. Elmo's fire can be found in Antonio Pigafetta's journal of his voyage with Ferdinand Magellan. St. Elmo's fire, also known as "corposants" or "corpusants" from the Portuguese ''corpo santo''"Corposants"
''The American Heritage Dictionary'' ("holy body"), is also described in ''The Lusiads'', the epic account of Vasco da Gama's voyages of discovery.

Robert Burton

Robert Burton wrote of St. Elmo's fire in his '' Anatomy of Melancholy'' (1621): "Radzivilius, the Lithuanian duke, calls this apparition ''Sancti Germani sidus''; and saith moreover that he saw the same after in a storm, as he was sailing, 1582, from Alexandria to Rhodes". This refers to the voyage made by Mikołaj Krzysztof "the Orphan" Radziwiłł in 1582–1584.

John Davis

On 9 May 1605, while on the second voyage of John Davis commanded by Sir Edward Michelborne to the East Indies, an unknown writer aboard the ''Tiger'' describes the phenomenon: "In the extremity of our storm appeared to us in the night, upon our maine Top-mast head, a flame about the bigness of a great Candle, which the Portugals call ''Corpo Sancto'', holding it a most divine token that when it appeareth the worst is past. As, thanked be God, we had better weather after it".

Pierre Testu-Brissy

Pierre Testu-Brissy was a pioneering French balloonist. On 18 June 1786 he flew for 11 hours and made the first electrical observations as he ascended into thunderclouds. He stated that he drew remarkable discharges from the clouds by means of an iron rod carried in the basket. He also experienced Saint Elmo's fire.Ballooning History, Who's Who.
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William Noah

William Noah, a silversmith convicted in London of stealing 2,000 pounds of lead, while en route to Sydney, New South Wales on the convict transport ship , recorded two such observations in his detailed daily journal. The first was in the Southern Ocean midway between Cape Town and Sydney and the second was in the Tasman Sea, a day out of Port Jackson:

While the exact nature of these weather phenomena cannot be certain, they appear to be mostly about two observations of St. Elmo's fire with perhaps some ball lightning and even a direct lightning strike to the ship thrown into the mix.

James Braid

On 20 February 1817, during a severe electrical storm, James Braid, surgeon at Lord Hopetoun's mines at Leadhills, Lanarkshire, had an extraordinary experience whilst on horseback:

Weeks earlier, reportedly on 17 January 1817, a luminous snowstorm occurred in Vermont and New Hampshire. Saint Elmo's fire appeared as static discharges on roof peaks, fence posts, and the hats and fingers of people. Thunderstorms prevailed over central New England.

Charles Darwin

Charles Darwin noted the effect while aboard the ''Beagle''. He 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:
He also describes the above night in his book The Voyage of the Beagle:

Richard Henry Dana

In ''Two Years Before the Mast'', Richard Henry Dana, Jr., describes seeing a corposant in the horse latitudes of the northern Atlantic Ocean. However, he may have been talking about ball lightning; as mentioned earlier, it is often erroneously identified as St. Elmo's fire:

The observation by RH Dana of this phenomena in Two Years Before the Mast is a straightforward description of an extraordinary experience apparently only known to mariners and airline pilots.

Nikola Tesla

Nikola Tesla

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