Jul 24th 2020

Superbolt Lightning Strikes With Surprises


Lightning and the thunder that it triggers are among the most spectacular of common weather events. Ancient peoples imagined their angry gods hurling lightning bolts, and modern horror filmmakers still rely on lightning as a surefire way to jolt an audience.

On average, lightning strikes somewhere in the world about half a dozen times every second. Thus, reports Science magazine, a network of some 100 lightning-detecting radio stations detected around 2 billion lightning strikes between 2010 and 2018.

The lightning tracking study also offered insight into a phenomenon that scientists are only beginning to understand: so-called superbolt lightning that strikes with a thousand times the energy of ordinary lightning bolts.

Lightning Striking Again

The detection network “listened” for lightning strikes by tuning to the very low frequency radio band from 5 to 18 kilohertz, a band in which lightning strikes are readily detected. Most of the strikes it detected released in the neighborhood of a thousand joules of energy within that band.

But very occasionally — about once in 250,000 lightning strikes, according to Weatherology — the network detected a strike that was enormously more powerful, releasing more than a million joules of radio energy. And because the very low frequency radio band used by the detector network accounts for only a small fraction of lightning strike energy, the superbolt lightning strikes, reports Science, may range in total energy from 10 billion to a trillion joules.

How much energy is that? The most powerful lightning strike releases about as much energy as a low-yield nuclear weapon, a quarter kiloton of TNT.

Striking Surprises

But the study of worldwide lightning strikes, led by Robert Holzworth of the University of Washington, did more than simply confirm the existence of superbolt lightning.

According to Futurity, the study also found that these most powerful lightning strike events are not just amped-up versions of ordinary lightning. Instead, they have a very different distribution pattern in both season and location.

Most lightning takes place over land (about 90% of observed strikes), and it’s most frequently observed during summer thunderstorms — especially in the “lightning chimney” regions of tropical and subtropical Africa and the Americas, and the islands of Southeast Asia.

Superbolt lightning, in contrast, appears most often in October and November, and mainly in the northern hemisphere. It usually strikes at sea, concentrated especially in the North Atlantic and Mediterranean regions, with another concentration near South America’s Andes mountains.

And Whole New Questions

The occurrence of superbolts also varies widely from year to year. The study recorded the most superbolt lightning strikes in 2013, and a lesser spike in 2014, while far fewer events were recorded in the other years.

The study authors speculate that this pattern may be linked to the sunspot cycle, or to cosmic rays. But when it comes to understanding superbolt lightning, you can’t look up the answers in the back of the book because that book is still being written.

Science Daily quotes study lead author Holzworth as saying of the possible explanations, “We’re leaving that as stimulation for future research.”

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