The Hunga Tonga-Hunga Ha’apai eruption, which produced the most powerful atmospheric explosion on record, also produced a record number of lightning strikes in a supercharged thunderstorm that lasted 11 hours and spread over 150 miles (240), a new study says. .
The volcano, located in the South Pacific Ocean, began to erupt in December 2021, but most explosive did not occur until January 15, 2022. Although the caldera of the volcano was 500 feet (150 meters) below sea level, the explosion exploded through the lake, sending plumes of ash 35 miles (58 km) high at an eruption rate. of 11 billion pounds (5 billion kilograms) per second—an order of magnitude greater than the eruption of Mount St. Helens in May 1980.
“There are theoretical limits to how high a plume can go and how fast an eruption can be, and the Hunga Tonga eruption broke them all,” said the study’s lead author, Alexa Van Eaton of the US Geological Survey. Space.com.
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Another record broken by the eruption was the number of lightning strikes. The jump produced the most powerful lightning storm ever observed, 2,600 flashes per minute at its peak and a total of about 192,000 flashes over 11 hours. What’s more, this lightning storm occurred at an unprecedented height of between 12 and 19 miles (20 to 30 km), higher than any lightning strike seen before. These lightning strikes were detected both by a network of radio antennas designed to monitor storms and by two spacecraft orbiting the Earth, GOES-17 satellite operated by the US National Oceanic and Atmospheric Administration (NOAA) and the Japan Meteorological Agency’s Himawari-8 satellites.
“We’ve never seen anything like this high speed lightning before and at this high altitude,” Van Eaton said.
The satellite images show that the lightning was not randomly distributed across the plume, but occurred in several concentric rings that appeared to be connected to each of the volcanic eruptions. As the plume lifted, it bent outwards and formed an “umbrella cloud” where the overflowing material fell onto it and oscillated around a neutral buoyancy layer.
“This caused a vertical movement into the cloud that was so huge that the wave moving out from the center of the jet was 10 vertical kilometers [6 miles] peak to trough,” said Van Eaton. This fluctuating pressure wave, also known as a gravity wave (not to be confused with gravitational waves since the merger black hole or neutron stars), was the source of the lightning.
There are two ways that the lightning could have formed within this circular gravitational wave. Since the Hunga Tonga eruption took place underwater, it ejected a large amount of water Earth’s atmosphere, the resulting ice crystals take on positive and negative charges. In addition, some of the ash formed from fragmented rock and magma blown into the air during the eruption is ionized, resulting in more positively and negatively charged areas. It is the gradient in electrical charge that suddenly ignites a lightning spark.
While lightning rings have been seen in volcanic eruptions before, the Hunga Tonga eruption was the first time multiple rings were seen – four in total, matching the four phases of the eruption – and the lightning rode the plunging rings like surfboards on ocean waves.
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Lightning rings are also called “lightning holes” because inside the ring there is usually no lightning. However, this was just another way in which the Hunga Tonga eruption was different: the holes began to fill with lightning within minutes of the gravitational wave passing. The mechanism that caused this fulfillment is still unclear.
Regardless, the presence of lightning highlights how electrical flashes could be used to provide early warning of volcanic eruptions. Volcanologists usually have to wait 10 minutes or so for an Earth-orbiting satellite to detect and photograph an eruption and alert emergency services, by which time the tsunamis could have drowned coastal regions, hurricanes flooded trees and homes, pyroclastic flows wiped out dozens. square kilometers and ash revved up airplane engines. Lightning, on the other hand, is found at radio frequencies at the speed of light. It goes without saying that this is faster than satellites, winds, seismic waves and infrasound.
Besides breaking records today, the Hunga Tonga eruption could also teach us about volcanism on the early Earth, and even possibly on other celestial bodies. The eruption is a type referred to as a phreatoplinian volcano, which occurs when a large amount of molten rock erupts through a thick layer of water. Explosives from an underwater volcano on this scale have only previously been seen in the geologic record.
Furthermore, the eruption could “probably affect how lightning travels to other planets, such as Venusor other planetary bodies that would not normally support conventional lightning,” Van Eaton said.
Evidence of active volcanism on Venus was discovered earlier this year, in an archive from NASA’s Magellan mission to the second planet from the sun. However, volcanism is high Jupiter moon Iobut types of cryovolcanism occur on Saturn moon Enceladus and possibly also Jovian satellites Europe.
“Enceladus has big jets of water that just shoot off. Could they support lightning?” Van Eaton asked. “I don’t know, but it seems like it’s a way to create a lot of atmospheric disruption that we haven’t thought of for other worlds.”
The study was published online today (June 19) in the journal Geophysical Research Letters.
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