TAMPA, Fla. – Air Force pilots evacuating MacDill Air Force Base in Tampa ahead of Hurricane Idalia caught amazing footage of what looks like lightning but really isn’t. It’s an extraordinary phenomenon known as St. Elmo’s Fire which has been regarded by sailors for generations as a good omen, warning the crew of imminent lightning strikes.
Science behind St. Elmo’s Fire
St. Elmo’s Fire is a phenomenon that involves a gap in electrical charge. It’s kind of like lightning, but not quite and it’s definitely not fire like the name insinuates.
The phenomenon is ionized air that emits a glow known as plasma. It’s more of a sparking of electrons versus lightning which is the movement of electricity from a charged cloud to the ground.
All aircraft on the installation have been evacuated/secured in preparation for #HurricaneIdalia . During the evacuation, the 50th ARS recorded St. Elmo’s fire, a weather phenomenon in which luminous plasma is created in an atmospheric electric field. pic.twitter.com/tqUGhfm8iN
— MacDill AFB (@MacDill_AFB) August 29, 2023
In a thunderstorm, the atmosphere is highly electrically charged. Between the clouds and the ground, the charge difference creates voltage. It’s in this area that atoms go through changes. Electrons move farther away from protons. This movement allows the electrons to move around more freely, making the air a good conductor of electricity. As the distance between the electrons and protons increases, ionization occurs.
The phenomenon occurs when a very strong electrical current comes into contact with an object like the mast of a ship or the wing of an airplane.
St. Elmo’s Fire can appear as a glow on a masthead that’s produced by an extreme buildup of electrical charge like during Idalia. The light we see is the result of air molecules tearing apart. In the case of St. Elmo’s fire, the nitrogen and oxygen in our atmosphere glows blue. Different gases in the atmosphere will glow different colors when becoming plasma.
Why it’s different from lightning
St. Elmo’s Fire doesn’t cover as much area as a lightning strike, appearing like sparking in the air. Lightning is a larger, more direct movement and appears bright white when moving from the clouds to the ground. Keep in mind, the atmosphere is conducive for lightning when St. Elmo’s Fire appears due to the strong electrical charge in the air.
Mariners use it as a sign of imminent lightning. According to NOAA, mariners should move to shelter when St. Elmo’s Fire appears because lightning could strike the mast within 5 minutes after the mast begins to glow.
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