Saint Elmo's fire

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St. Elmo's fire on a ship at sea

St. Elmo's fire (also St. Elmo's light^[1][2]) is a weather phenomenon in which luminous plasma is created by a coronal discharge from a grounded object in an electric field in the atmosphere (such as those generated by thunderstorms created by a volcanic eruption)

St. Elmo's fire is named after St. Erasmus of Formiae (also called St. Elmo, the Italian name for St. Erasmus), the patron saint of sailors. The phenomenon sometimes appeared on ships at sea during thunderstorms and was regarded by sailors with religious awe for its glowing ball of light, accounting for the name.^[3]

Characteristics

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.^[4] Often accompanying the glow is a distinct hissing or buzzing sound. It is sometimes confused with ball lightning.

In 1750, Ben 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.^[5][6]

Scientific explanation

St. Elmo's fire is a mixture of gas and plasma, as are flames in general and stars. 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 1000 volts per centimeter induces 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 ends of pointed objects.

Conditions that can generate St.Elmo's fire are present during thunderstorms, when high voltage levels are present between clouds and the ground underneath. Air molecules glow due to the effects of such voltage, producing St. Elmo's fire.

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.^[7]

Notable observations

In ancient Greece, the appearance of a single one was called Helena and two were called Castor and Pollux. Occasionally, it was 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.^[8]

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".^[9]

The Chinese sea-goddess Mazu is believed to create an ethereal flame atop the mast of ships to guide and bless lost sailors. In China, St. Elmo's fire is colloquially known as the "fire of Mazu".

References to St. Elmo's fire can be found in the works of Julius Caesar (De Bello Africo, 47), Pliny the Elder (Naturalis Historia, book 2, par. 101) , and 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^[10] ("holy body"), was a phenomenon described in The Lusiads.

Robert Burton wrote of St. Elmo's fire in his Anatomy of Melancholy: "Radzivilius, the Polonian 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.

On Thursday February 20, 1817,^[11] during a severe electrical storm James Braid, then surgeon at Lord Hopetoun's mines at Leadhills, Lanarkshire, had an extraordinary experience whilst on horseback:

On Thursday 20th, I was gratified for a few minutes with the luminous appearance described above [viz., "such flashes of lightning from the west, repeated every two or three minutes, sometimes at shorter intervals, as appeared to illumine the whole heavens"]. It was about nine o'clock, P.M. I had no sooner got on horseback than I observed the tips of both the horse's ears to be quite luminous: the edges of my hat had the same appearance. I was soon deprived of these luminaries by a shower of moist snow which immediately began to fall. The horse's ears soon became wet and lost their luminous appearance; but the edges of my hat, being longer of getting wet, continued to give the luminous appearance somewhat longer. I could observe an immense number of minute sparks darting towards the horse's ears and the margin of my hat, which produced a very beautiful appearance, and I was sorry to be so soon deprived of it. The atmosphere in this neighbourhood appeared to be very highly electrified for eight or ten days about this time. Thunder was heard occasionally from 15th to 23d, during which time the weather was very unsteady: frequent showers of hail, snow, rain, &c. I can find no person in this quarter who remembers to have ever seen the luminous appearance mentioned above, before this season,—or such a quantity of lightning darting across the heavens,—nor who have heard so much thunder at that season of the year. This country being all stocked with sheep, and the herds having frequent occasion to pay attention to the state of the weather, it is not to be thought that such an appearance can have been at all frequent, and none of them to have observed it.

— ^[12]

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:

Everything is in flames, — the sky with lightning, — the water with luminous particles, and even the very masts are pointed with a blue flame.

— ^[13]

St. Elmo's fire is reported to have been seen during the Siege of Constantinople by the Ottoman Empire in 1453. It reportedly was 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.

In Two Years Before the Mast, Richard Henry Dana, Jr. describes seeing a corposant in the southern Atlantic Ocean. However, he may have been talking about ball lightning; as mentioned earlier it is often erroneously identified as St. Elmo's fire: "There, directly over where we had been standing, upon the main top-gallant mast-head, was a ball of light, which the sailors name a corposant (corpus sancti), and which the mate had called out to us to look at. They were all watching it carefully, for sailors have a notion, that if the corposant rises in the rigging, it is a sign of fair weather, but if it comes lower down, there will be a storm".^[14]

Many Russian sailors have seen them throughout the years. To them, they are "Saint Nicholas" or "Saint Peter's lights".^[9] They were also sometimes called St. Helen's or St. Hermes' fire, perhaps through linguistic confusion.^[15]

Shortly before the crash of the Luftschiffbau Zeppelin's LZ 129 Hindenburg in 1927, Professor Mark Heald of Princeton saw St. Elmo's Fire flickering along the airship's back a good minute before the fire broke out. Standing outside the main gate to the Naval Air Station, he watched, together with his wife and son, as the airship approached the mast and dropped her bow lines. A minute thereafter, by Mr. Heald's estimation, he first noticed a dim "blue flame" flickering along the backbone girder about one-quarter the length abaft the bow to the tail. There was time for him to remark to his wife, "Oh, heavens, the thing is afire," for her to reply, "Where?" and for him to answer, "Up along the top ridge" - before there was a big burst of flaming hydrogen from a point he estimated to be about one-third the ship's length from the stern.^[16]

St Elmo's fire were also seen during the Great Chicago Fire in Kansas and Oklahoma (US).^[17]

Accounts of Magellan's first circumnavigation of the globe refer to St. Elmo's fire being seen around the fleet's ships multiple times off the coast of South America. The sailors saw these as favorable omens.

On August 26, 1883, the British warship Charles Ball sailing the Sunda Strait en-route to Hong Kong came within 20 km of the exploding Krakatau volcano and witnessed a great deal of static electricity in the atmosphere, generated by the movement of tiny particles of rocks and droplets of water from the volcano's steam, which caused spectacular brush discharges taking place from the masts and rigging of the ship.

Among the phenomena experienced on British Airways Flight 9 on June 24, 1982 were glowing light flashes along the leading edges of the aircraft, which were seen by both passengers and crew. While it 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.^[18][19]

The ill-fated Air France Flight 447 flight from Rio de Janeiro-Galeão (GIG) to Paris-Roissy (CDG) is understood to have experienced St. Elmo's fire 23 minutes prior to crashing into the Atlantic Ocean. The tropical storm system that gave rise to the phenomena was a key factor in the Airbus A330-200's eventual crash.^[20]

In literature

One of the earliest references to the phenomenon appears in Alcaeus's Fragment 34a about the Dioscuri, or Castor and Pollux. It is also referenced in Homeric Hymn 33 to the Dioscuri who were from Homeric times associated with it. Whether the Homeric Hymn antedates the Alcaeus fragment is unknown.

Also in The Castaways of the Flying Dutchman by Brian Jacques St. Elmo's Fire is mentioned.

The phenomenon appears to be described first in the Gesta Herwardi,^[21] written around 1100 and concerning an event of the 1070s. However, one of the earliest direct references to St. Elmo's fire made in fiction can be found in Ludovico Ariosto's epic poem Orlando furioso (1516). It is located in the 17th canto (19th in the revised edition of 1532) after a storm has punished the ship of Marfisa, Astolfo, Aquilant, Grifon, and others, for three straight days, and is positively associated with hope:

But now St. Elmo's fire appeared, which they had so longed for, it settled at the bows of a fore stay, the masts and yards all being gone, and gave them hope of calmer airs.

In Shakespeare's The Tempest (c. 1623), Act I, Scene II, St. Elmo's fire acquires a more negative association, appearing as evidence of the tempest inflicted by Ariel according to the command of Prospero:

PROSPERO

Hast thou, spirit, Perform'd to point the tempest that I bade thee?

ARIEL

To every article. I boarded the king's ship; now on the beak, Now in the waist, the deck, in every cabin, I flamed amazement: sometime I'ld divide, And burn in many places; on the topmast, The yards and bowsprit, would I flame distinctly, Then meet and join.

— Act I, Scene II , The Tempest

Later in 18th century and 19th century literature associated St. Elmo's fire with bad omen or divine judgment, coinciding with the growing conventions of Romanticism and the Gothic novel. For example, in Ann Radcliffe's The Mysteries of Udolpho (1794), during a thunderstorm above the ramparts of the castle:

"And what is that tapering of light you bear?" said Emily, "see how it darts upwards,—and now it vanishes!" "This light, lady", said the soldier, "has appeared to-night as you see it, on the point of my lance, ever since I have been on watch; but what it means I cannot tell". "This is very strange!" said Emily. "My fellow-guard", continued the man, "has the same flame on his arms; he says he has sometimes seen it before...he says it is an omen, lady, and bodes no good". "And what harm can it bode?" rejoined Emily. "He knows not so much as that, lady".

— Vol. III, Ch. IV , The Mysteries of Udolpho

Starbuck points out "corpusants" in Melville's novel Moby Dick during a thunder storm in the japanese sea in chapter 119 "The Candles".

In Hergé's twentieth title in the comic book series The Adventures of Tintin, Tintin in Tibet, Tintin recognizes the phenomenon on Captan Haddock's ice-axe.

In Kurt Vonnegut's Slaughterhouse-Five, when Billie Pilgrim sees the phenomenon on soldiers' helmets and on rooftops.

See also

• Ball lightning
• Foo fighter
• List of plasma (physics) articles
• Naga fireballs
• Triboelectric effect
• Will-o'-the-wisp

References

External links

Wikimedia Commons has media related to: St. Elmo's fire

• Picture of the Airbus A320-232 aircraft
• Video of St. Elmo's fire on YouTube
• The Fire Of St. Elmo