This fascinating light show is a type of continuous electrical discharge that occurs during storms.
With a duration that can range from a couple of minutes to several hours, St. Elmo’s fire creates a blue or violet glow that ‘dances’ around the ends of pointed objects, such as the nose or wings of aircraft, the masts of ships and even the bell towers of churches.
The phenomenon owes its name to Saint Erasmus of Formia, also known as Saint Elmo, the patron saint of sailors.
Due to its mysterious and ethereal appearance, St. Elmo’s fire has been the origin of many legends and superstitions among them, who considered it a sign of protection, as this shining light danced on the masts of ships when there was a storm.
St. Elmo’s fire is the first recorded form of the corona effect, or corona discharge.
It occurs when the atmosphere is highly charged with electricity during a storm, and the air molecules present in storm clouds or cumulonimbus clouds become ionised around pointed objects.
This ionization process, coupled with ambient humidity, produces a faint, bright plasma, usually blue or violet, that is visible in low light conditions.
And why blue? Because of the composition of the Earth’s atmosphere, mainly hydrogen and oxygen. If, for example, neon gas were the most abundant, St. Elmo’s fire would be seen in reddish and orange tones. Interesting, isn’t it?
Long before aviation, in the 18th century, Benjamin Franklin’s work was key to understanding St. Elmo’s fire. The scientist’s restless mind took this phenomenon out of the realm of superstition and into scientific understanding.
Franklin conducted pioneering experiments with electricity, including his famous kite experiment in a thunderstorm. His research led him to theorise that it was not a supernatural event, but a manifestation of atmospheric electricity.
In addition, he correctly concluded that pointed objects, such as ship masts, could concentrate electrical charges and create the bright plasma discharge we recognise as St. Elmo’s Fire.
In fact, his work laid the groundwork for the development of lightning rods as we know them, which have since saved countless lives and structures from lightning strikes.
Mentions of St. Elmo’s fire in history date back to ancient times. You know that sailors used to consider the eerie glow a good omen, a sign that their patron saint was watching over them during treacherous sea voyages.
Apparently, Saint Erasmus was a saint known for his miracles with fire. Even Portuguese sailors linked this phenomenon to their faith, calling it Pedro’s lights in honor of their saint.
In addition, historical texts from ancient Greece and Rome describe the phenomenon in great detail, highlighting its importance in maritime folklore. And even in the logbooks of famous expeditions such as Magellan’s voyage or the siege of Constantinople, the appearance of St. Elmo’s fire is mentioned.
On the other hand, it has also played an important role in aviation. Early pilots and aviators observed the glow on their aircraft during storms, often as a reassuring sign that their flight would withstand turbulence.
Understanding the origin of St. Elmo’s Fire is essential for today’s pilots. Although the phenomenon itself is harmless, it indicates the presence of strong electric fields and possible storm activity.
Pilots use this knowledge to navigate safely, avoiding severe weather conditions that could endanger their flights.
By recognising the blue or violet glow around aircraft components, they can know when to modify flight paths to avoid adverse weather conditions.
In addition, this electrical spectacle brings with it another handicap: it can interfere with radio communications, with the inconveniences that it can generate.
Among the atmospheric phenomena that could be observed in flight is also ball lightning, an extremely rare but potentially dangerous event.
These are electrical discharges that usually float or move in the air, adopting a spherical or oval shape. They are not very large, as they usually range between 10 and 40 centimetres, and the tones they acquire range from bright red to yellow.
After a few seconds, the discharge usually dissipates, being absorbed by some element or, on rare occasions, disappearing with an explosion.
Usually associated with thunderstorms, ball lightning has been observed in various locations but whenever they have appeared, the testimonies have been very disparate, so much so that there are still those who believe that they are more a myth than a reality.
