The odds of being struck by lightning are less than one in a million, but those odds dropped dramatically this month when more than 4.2 million lightning strikes were recorded in every Australian state and territory during the weekend of November 12 to 13.
Considering that each lightning strike travels over 320,000 kilometers per hour, that’s a huge amount of electricity.
Have you ever wondered about lightning? For the past 50 years, scientists around the world have debated why lightning zigzags and how it relates to the thunder cloud above.
There has been no definitive explanation so far, with a University of South Australia plasma physicist publishing a landmark paper that solves both mysteries.
Dr. John Lowke, a former CSIRO scientist and now an assistant research professor at UniSA, says the physics of lightning has baffled the best scientific minds for decades.
“There are a few textbooks on lightning, but none have explained how zig-zags (called steps) are formed, why the electrically conductive column connecting the steps to the cloud stays dark, and how lightning can travel for miles,” said said Dr. Lowke. said.
The answer? Metastable singlet-delta oxygen molecules.
Basically, lightning occurs when electrons strike oxygen molecules with enough energy to create high energy delta singlet oxygen molecules. After collision with the molecules, the “detached” electrons form a very conductive step – initially luminous – which redistributes the electric field by causing successive steps.
The conductive column connecting the step to the cloud remains dark as the electrons attach to the neutral oxygen molecules, followed by an immediate detachment of the electrons by the delta singlet molecules.
Why is this important?
“We need to understand how lightning is triggered so that we can better protect valuable buildings, planes, skyscrapers, churches and people,” says Dr Lowke.
Although it is rare for humans to be struck by lightning, buildings are struck many times, especially large and isolated ones (the Empire State Building is struck about 25 times a year).
The solution to protecting structures against lightning has remained the same for hundreds of years.
A lightning rod invented by Benjamin Franklin in 1752 is basically a thick fence wire that is attached to the top of a building and connected to the ground. It is designed to attract lightning and ground the electrical load, thus preventing the building from being damaged.
“These Franklin rods are needed for all buildings and churches today, but the uncertain factor is the number needed on each structure,” says Dr. Lowke.
There are also hundreds of structures that are currently unprotected, including shelters in the parks, often made of galvanized iron and supported by wooden poles.
This could change with new Australian lightning protection standards recommending that such roofs be earthed. Dr Lowke was a member of the Standards Australia committee recommending this change.
“Improved lightning protection is so important today due to more extreme weather events due to climate change. Additionally, as the development of environmentally friendly composite materials in aircraft improves efficiency energy, these materials greatly increase the risk of damage from lightning, so we need to consider additional protective measures.
“The more we know about how lightning occurs, the better informed we will be in designing our built environment,” says Dr Lowke.
The article, “Towards a Theory of Tiered Leaders in Lightning” is published in the Journal of Physics D: Applied Physics. It is authored by Dr John Lowke and Dr Endre Szili of the Future Industries Institute at the University of South Australia.
John J Lowke et al, Toward a theory of “stepped-leaders” of lightning, Journal of Physics D: Applied Physics (2022). DOI: 10.1088/1361-6463/aca103
Provided by the University of South Australia
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