Scientists detect ‘superbolts’ 1,000 times brighter than typical lightning strikes

Every now and then, Earth reminds us that it is capable of releasing furious energy.

Case in point: Scientists have just detected a new extreme in lightning activity hot spots called “ superbolts ”: intense lightning that shines up to 1,000 times brighter than typical lightning strikes.

The observations come from researchers at the US National Laboratory Los Alamos, who used satellites to measure extreme lightning events. The results force a rethinking of what constitutes a superbolt and shed new light on the origin and origin of superbolts.

“We want[ed] to see what the limits are [of superbolts] really are, said atmospheric scientist Michael Peterson The Washington Post. “It’s about their size and their brightness.”

Superbolts were first detected from satellite data in the 1970s, being described as lighting that outperforms average bolts by a factor of 100 or more.

Since then, atmospheric scientists have debated what really counts as a superbolt, as measurements taken by different instruments can vary.

“When you see a lightning bolt from space, it will look much darker than if you saw it from ground level, because the clouds block some of the light,” said Peterson, explaining how satellite measurements may differ from ground detectors. .

There is also the question of whether the superbolts are supercharged by a single phenomenon, or if they are simply bigger, brighter strikes of the usual lightning variety.

“Understanding these extreme events is important because it tells us what lightning is capable of,” said Peterson, who has detected record lightning strikes in recent years – including a 2018 mega-flash (long-lasting lightning burst) that s ‘is extended over 700 kilometers. (440 miles) across the sky and lasted almost 17 seconds.

In a new study, Peterson and his colleague Erin Lay analyzed data collected by NASA’s Geostationary Lightning Mapper, a detector attached to weather satellites and sent into orbit to record lightning, day and night, over the Americas and the oceans. adjacent every two milliseconds. .

Unlike ground surveillance systems, which detect radio waves, the GLM measures the total brightness (optical energy) of lightning in clouds, between clouds, plus lightning hitting the ground.

(Michael Peterson / Los Alamos National Laboratory)

Above: A superbolt lasting nearly 7 seconds captured by the Geostationary Lightning Mapper over the southeastern United States in February 2019.

Researchers combed through two years of data on lightning strikes that glowed 100 times brighter than a typical lightning bolt detected from space, and found about 2 million events intense enough to be called super- lightning – about one in 300 lightning events.

Just keep in mind that some superbolts may have looked brighter than other strikes, if they were on the edge of a thunderstorm cloud and the satellite finder had a cloudless view.

When the researchers raised the bar for lightning events to be at least 1,000 times brighter than an ordinary lightning strike, they identified key hotspots of energetic supercoat activity.

The most radiant cases were concentrated in the central United States and in the Rió de La Plata basin, which spans Uruguay, Paraguay and parts of Argentina and Brazil.

However, the GLM detector may not have captured every superbolt. Although the satellites are fixed over the Americas, from Alaska in the north to the southern tip of Argentina, GLM measures the most energetic lightning, but not necessarily the most powerful lightning, if they are shorter than 2 milliseconds.

“[U]singing the total energy to track down the brightest lightning bolts will miss short-lived but extremely powerful optical pulses, ”the study authors write in their paper.

There was, however, a significant overlap with the superbolts identified by the Los Alamos researchers in a second study, which ranked superbolts based on their peak power – in the same way these extreme events had been defined for. the first time.

In the second study, the researchers analyzed 12 years of data from another satellite and counted lightning strikes as super-bolts if they produced 100 gigawatts of power. For comparison, that’s more power in a single bolt than all solar panels in the United States combined.

“A lightning strike even exceeded 3 terawatts of power – thousands of times stronger than ordinary lightning detected from space,” Peterson said.

By combining satellite data with ground measurements, the researchers also discovered that superbolts are indeed another type of lightning.

The strongest superbolts (producing over 350 gigawatts of power) were the result of rare positively charged cloud-to-ground events, rather than negatively-charged cloud-to-ground events, which characterize most lightning strikes.

The results also showed that superbolts often occur over the ocean and tend to cause mega-flashes, which stretch for hundreds of kilometers horizontally from tip to tail.

“Ocean storm systems, especially during winter, and particularly those located around Japan, produce these intense super-aerobatics,” the researchers explain in the second article.

This is somewhat in line with the results of a 2019 study, which found that super bolts formed mostly over oceans and seas, although this research detected most of the super bolts in the Atlantic. North, west of Europe.

So the issue is by no means settled. Atmospheric scientists must continue to compare measurements from different instruments on the ground and in orbit to understand the differences between them and to better characterize extreme lightning events.

“It will be an important undertaking of the atmospheric electricity community to reconcile the main events recorded by the different [ground-based radio-frequency] instruments and then come to a consensus on what is – and what is not – a superbolt, ”the researchers write.

Both articles were published here and here in the Journal of Geophysical Research: Atmospheres.