St. Elmo’s Fire

The power of the goddess, having indeed been manifested in previous times, has been abundantly revealed in the present generation. In the midst of the rushing waters it happened that, when there was a hurricane, suddenly a divine lantern was seen shining at the masthead, and as soon as that miraculous light appeared the danger was appeased, so that even in the peril of capsizing one felt reassured and that there was no cause for fear.

— Admiral Zheng He, 15th Century

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

— Charles Darwin, 1832

Today we investigate not the 1985 Joel Schumacher coming-of-age film but a weather phenomenon that has beguiled and transfixed humans for millennia.

This odd happening is sometimes called witchfire, witch’s fire, or corpusants, but is more commonly known as St. Elmo’s fire.

These names belie the ancient connection humans have to the spectacle; they also imply competing sides of a mystery in regard to its origins. “Corpusant” derives from the Portuguese words corpo and santo, which translates to “holy body.” Some sailors believed St. Elmo’s fire to be the embodiment of a saint or some other sacrosanct entity. If not a literal body, others thought it to be fire from powerful beings. Witches would wield something evil, whereas St. Erasmus of Formia – better known as St. Elmo and the patron saint of sailors – might employ a flame of protection or good omens.

Whatever the name, St. Elmo’s fire was known well by seafarers in the ancient world because it often happened on boats. The phenomenon presents as a blue or violet glow around an object, many times coupled with hissing or buzzing. As it turns out, masts happen to be incredible conductors for corpusants, but they’re not the only things that produce them.
A black-and-white painting of a sailboat with glowing plasma emitting from the masts
St. Elmo's Fire on Mast of Ship at Sea, in The Aerial World, by Dr. G. Hartwig, London, 1886

St. Elmo’s fire is luminous plasma made by corona discharges from rods or pointy objects.

The preceding sentence might sound like science jargon, but the concept isn’t too complicated or even unfamiliar. Plasma is the fourth state of matter, distinct from solids, liquids, and gases because it is composed largely of charged particles. Though plasma might appear most like a gas, it differs in several key factors. Plasma might materialize in our daily lives the least, but it’s actually the most abundant phase of matter throughout the universe. Stars and the interstellar medium are composed of plasma. On a more terrestrial level, you might encounter it in a few ways. Lightning, neon signs, auroras, and the namesake televisions are all forms of or contain plasma.

Neon signs are perhaps the most apt analogy for St. Elmo’s fire. The color you see inside the sign is caused by the excitement – aka ionization – of the gas inside the tubes. In the natural phenomenon, an electrical field, often caused by a coming thunderstorm, produces ionization of air molecules. Electrical fields tend to concentrate in areas of high curvature. What objects feature spots of sudden, high curvature? Pointy things! When the strength of an electrical field overcomes the dielectric strength of the air (the ability to insulate from electric charges), a corona discharge occurs.

The discharge often appears as a blue or violet glow because of the gases in our atmosphere. Oxygen and nitrogen fluoresce in blue and purple visible light. Other gases, such as neon, produce varying colors. Though not a natural manifestation of St. Elmo’s fire, the following photograph displays corona discharges that happen frequently on overhead power lines:

Time-lapse photo of an electricity transformer with glowing blue corona discharges emanating from it
Long exposure photograph of corona discharge on an insulator string of a 500 kV overhead power line - photo by Nitromethane

Human history is filled with incidents of St. Elmo’s fire.

Sailors viewed the glow as a positive portent, despite the fact that it often accompanies a thunderstorm (perhaps because they viewed them toward the end of the storms). Herman Melville placed corpusants in a Moby-Dick chapter called “The Candles.” Welsh seafarers called the fire “candles of the Holy Ghost” or “candles of St. David.” To Russian mariners, they were “Saint Peter’s lights.” Magellan’s crew believed they were blessed when they witnessed the fire in South America. William Bligh witnessed it on HMS Bounty. Charles Darwin watched the “natural fireworks” aboard the Beagle.

St. Elmo does limit his fire to ships, however. Humans have encountered the phenomenon in various landlubbing situations, as well.

Julius Caesar’s troops watched the tips of their spears glow during a campaign in Africa. During the 1453 siege of Constantinople, the Byzantines saw it flowing from the apex of the Hippodrome. They believed it was a sign the invading Ottomans would be extinguished; instead, Constantinople fell days later. Nikola Tesla produced the fire during his experiments with coils in Colorado, purportedly lighting up butterflies as they flitted about. On the way to deliver the Fat Man atomic bomb to Nagasaki in 1945, the B-29 Superfortress experienced the marvel, with the pilots noting it was “as though we were riding the whirlwind through space on a chariot of blue fire.”

Likewise, Melville does not have a literary monopoly on the fire. Ariel notes witchfire to Prospero in Shakespeare’s The Tempest. Samuel Taylor Coleridge’s Ancient Mariner rimes about “dearth fires” dancing. Kurt Vonnegut’s Billy Pilgrim spies the fire from the top of the helmets of soldiers and roofs in Slaughterhouse-Five.

It’s easy to see why such a happening would impress upon humans throughout the ages. What’s interesting about St. Elmo’s fire is that it feels like a “modern” phenomenon that just happens to present in ways many non-modern humans could see it. By “modern” I mean that we had no insight into plasma or how to create it until recent times, yet the fire could emerge from a ship’s mast just by sailing into ionized air. These candles must truly have seemed to be otherworldly, an eerie emanation from beyond the mortal realm.

Despite the myriad examples, St. Elmo’s fire is relatively rare in terms of documentation. Only recently have we had the means to photograph or record the happening. It’s so fleeting that footage is hard to come by. In the past several decades, photos have emerged from flight decks, as airliners move toward thunderstorms, though the fire does not appear in the common glow-form. This version of St. Elmo’s fire looks more like St. Elmo’s lightning bolts.

Pilots in an airliner look on as lightning-bolt-like manifestations of St. Elmo's fire crosses the windscreen
Airmen experience St. Elmo's fire while flying a KC-10 aircraft in 2017 - photo by Senior Airman Brian Kelly

However, a few fortunate souls have managed to snag the fire in motion.

The phenomenon usually requires a tower, a steeple, a rod, or a wing, but humans have pointy things on their bodies that can create St. Elmo’s fire.

This incredible video captures the fire coming from fingers!

Recorded video of St. Elmo’s fire that approximates the painting in today’s first image is difficult to discover.

In another example of how awesome, destructive natural forces can also produce sublime beauty, Hurricane Idalia, which battered Florida in August 2023, produced magic. As pilots evacuated from MacDill Air Force Base near Tampa, they experienced St. Elmo’s fire in a fashion similar to the image from the flight deck above. However, if you look closely at the edge of the left wiper, you can see the constant glow of luminous plasma!

That tiny, constant discharge is likely similar to what ye olde sailors of ages ago witnessed, though probably in larger doses.

Truly spectacular.

St. Elmo’s fire joins the wish list of natural phenomena to witness before shuffling off the mortal coil. Short of becoming a pilot or a sailor, the rest of us might have a better chance of seeing corpusants than we might guess. According to MIT, a fantastic source of St. Elmo’s fire is a cell tower.

Time to place myself near these metallic, pointy edifices when the next thunderstorm rolls in. What could go wrong? St. Elmo’s fire is a positive omen, right?

Become a patron at Patreon!

Leave a Comment

Your email address will not be published. Required fields are marked *