St. Elmo's fire

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 horn 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.
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.
In an August 2020 paper, MIT demonstrated that St. Elmo's fire behaves differently in airborne objects versus grounded structures.
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" ("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.&lt;ref name="Ballooning Who's Who"/
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 R. H. Dana of this phenomenon 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 created St. Elmo's fire in 1899 while testing a Tesla coil at his laboratory in Colorado Springs, Colorado, United States. St. Elmo's fire was seen around the coil and was said to have lit up the wings of butterflies with blue halos as they flew around.
Mark Heald.
A minute before the crash of the Luftschiffbau Zeppelin's LZ 129 "Hindenburg" on 6 May 1937, Professor Mark Heald (1892–1971) of Princeton saw St. Elmo's Fire flickering along the airship's back. 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 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.
William L. Laurence.
St. Elmo's fire was reported by "The New York Times" reporter William L. Laurence on August 9, 1945, as he was aboard "Bockscar" on the way to Nagasaki.
In popular culture.
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.
The phenomenon appears to be described first in the "Gesta Herwardi", 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:
In William 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:
The fires are also mentioned as "death fires" in Samuel Taylor Coleridge's "The Rime of the Ancient Mariner":
Later in the 18th and 19th centuries, literature associated St. Elmo's fire with a 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:
In the 1864 novel "Journey to the Center of the Earth" by Jules Verne, the author describes the fire occurring while sailing during a subterranean electrical storm (chapter 35, page 191):
In Herman Melville's novel "Moby-Dick", Starbuck points out "corpusants" during a thunder storm in the Japanese sea in chapter 119, "The Candles".
St. Elmo's fire makes an appearance in "The Adventures of Tintin" comic, "Tintin in Tibet", by Hergé. Tintin recognizes the phenomenon on Captain Haddock's ice-axe.
The phenomenon appears in the first stanza of Robert Hayden's poem "The Ballad of Nat Turner"; it is also referred to with the term "corposant" in the first section of his long poem "Middle Passage".
In Kurt Vonnegut's "Slaughterhouse-Five", Billy Pilgrim sees the phenomenon on soldiers' helmets and on rooftops. Vonnegut's "The Sirens of Titan" also notes the phenomenon affecting Winston Niles Rumfoord's dog, Kazak, the Hound of Space, in conjunction with solar disturbances of the chrono-synclastic infundibulum.
In Robert Aickman's story "Niemandswasser" (1975), the protagonist, Prince Albrecht von Allendorf, is "known as Elmo to his associates, because of the fire which to them emanated from him". "There was an inspirational force in Elmo of which the sensitive soon became aware, and which had led to his "Spottname" or nickname."
In "On the Banks of Plum Creek" by Laura Ingalls Wilder, St. Elmo's fire is seen by the girls and Ma during one of the blizzards. It was described as coming down the stove pipe and rolling across the floor following Ma's knitting needles; it did not burn the floor (pages 309–310). The phenomenon as described, however, is more similar to ball lightning.
In "Voyager", the third major novel in Diana Gabaldon's popular Outlander series, the primary characters experience St. Elmo's fire while lost at sea in a thunderstorm between Hispaniola and coastal Georgia.
St. Elmo's fire is also mentioned in the novel, "Castaways of the Flying Dutchman" by Brian Jacques.
In television.
On the children's television series "The Mysterious Cities of Gold" (1982), episode four shows St. Elmo's fire affecting the ship as it sailed past the Strait of Magellan. The real-life footage at the end of the episode has snippets of an interview with Japanese sailor Fukunari Imada, whose comments were translated to: "Although I've never seen St. Elmo's fire, I'd certainly like to. It was often considered a bad omen, as it played havoc with compasses and equipment". The TV series also referred to St. Elmo's fire as being a bad omen during the cartoon. The footage was captured as part of his winning solo yacht race in 1981.
On the American television series "Rawhide", in a 1959 episode titled "Incident of the Blue Fire", cattle drovers on a stormy night see St. Elmo's fire glowing on the horns of their steers, which the men regard as a deadly omen. St. Elmo's fire is also referenced in a 1965 episode of "Bonanza" in which religious pilgrims staying on the Cartwright property believe an experience with St. Elmo's fire is the work of Satan.
On the Netflix original animated series "Trese" (2021), the Santelmo (St. Elmo's Fire) is one of the protagonist's, Alexandra Trese's, allies whom she contacts using her old Nokia phone, dialing the date of the Great Binondo fire, 0003231870.