What is this phenomenon all about? On his expeditions, Christopher Columbus sighted it in the night sky during a storm. It was also seen by Charles Darwin on a “cold and raw” voyage near the Rio de la Plata. What is the spectacular “San Telmo fire” about?
Both explorers were talking about a particular atmospheric phenomenon. Several factors combine to create an imposing electromagnetic discharge. It is usually interpreted as lightning, although it is not what it is. Recently, the spectacle was seen this Tuesday by pilots of a U.S. Air Force plane.
It was named for centuries as “San Telmo’s fire”, in honor of the saint of sailors. The sailors of antiquity told of having seen it during the nights at sea. As Darwin recounted, it was seen as a glow that shot from the tips of the ships’ masts.
Centuries later, atmospheric scientists came up with an explanation for this phenomenon. It is produced “by an extreme buildup of electrical charge.” The U.S. National Oceanic and Atmospheric Administration (NOAA) explains. “It happens when a pointed object (such as a ship’s mast) comes in contact with an extraordinarily high electric field and a large number of electrons. The electrons can glow in various colors, like a neon sign. And that results in this rare phenomenon,” NOAA notes.
The electric field can convert air molecules into electrically charged particles or “plasma,” which emit a glowing light. The result generates a discharge. Not lightning as in a regular thunderstorm, but plasma lightning. Today, merchant ships do not use the old masts. But some shaped parts, including lightning rods, can pick up this energy.
In the deep darkness
Aircraft wings can also be exposed. But this does not represent a danger to those traveling sheltered inside. A similar glow can be created in a laboratory. The spectacular “San Telmo fire” is more impressive in certain circumstances over the centuries. It is when it occurs on stormy nights over the sea, where the darkness is deepest.