The eruption of the Hunga submarine volcano in Tonga last year not only created the largest plume ever seen, but also generated a record number of volcanic lightning strikes.
On January 15, 2022, after months of activity, a giant volcanic plume erupted beneath the South Pacific sea in an explosion so huge it was visible from space. A tower of ash soared into the stratosphere and beyond, reaching a record height of more than 35 miles high – the first known plume to reach the mesosphere.
But as the cloud spread like an umbrella, lightning began to appear, all part of a supercharged thunderstorm that lasted 11 hours.
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At its peak, the storm generated more than 2,600 lightning strikes per minute, with about 192,000 recorded in total.
However, the lightning did not happen randomly. As the plume continued to expand, eventually reaching 150 miles in diameter, the lightning formed in concentric rings, riding the waves of the cloud as it rose and fell – sometimes up to six miles up and down. .
While rings of lightning have been observed before, the four distinct phenomena recorded following the Tonga eruption are a first.
What is lightning?
Lightning is the electrical discharge between positively and negatively charged regions in clouds. The electrical discharge serves as an equalizing process between charged regions and can travel from cloud to cloud, cloud to ground, or cloud to air.
Source: NASA
“We’ve never seen anything like this before, and at such high altitudes,” lead author Alexa Van Eaton said, speaking to space.com.
Of the record-breaking plume, he added: “There are theoretical limits to how high a plume can be and how fast the rate of eruption can be, and the Hunga Tonga eruption just shattered them all. “
How the lightning formed has yet to be determined, with two possible explanations. The vast volume of water sprayed into the atmosphere would have quickly turned into ice crystals, taking on positive and negative charges in the same way lightning forms in typical cumulonimbus clouds.
Alternatively, rock and magma ejected from the volcano itself could have charged.
In the cloud, the positive and negative group charge particles separate into two groups, but remain attracted to each other as they move away, causing a flash between the two when the force increases enough.
The findings may also deepen our understanding of how lightning is triggered elsewhere in the solar system.
‘[It could] have implications for how lightning strikes on other planets, such as Venus, or other planetary bodies that would typically not support traditional lightning,” said Van Eaton of the US Geological Survey.
‘[Saturn’s moon] Enceladus has great jets of water gushing out. Could they withstand lightning? I don’t know, but it seems to be a way to create a major atmospheric disturbance that we haven’t really thought about for other worlds.
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