Hunga Tonga volcano eruption hits space

When the Hunga Tonga-Hunga Ha’apai volcano in the Pacific Ocean erupted earlier this year, the event was one of the record-breaking events – in many surprising ways.

The January 15 eruption was so explosive that it injected water vapor so high it touched space, a first sighting of its kind for an Earth volcano. And the event produced the largest concentration of lightning ever detected, making it far flashier than the 2018 Krakatau eruption in Indonesia or the 2021 tornado outbreak in the southern United States.

The eruption also released so much energy that its disruption of a charged layer of Earth’s atmosphere, called the ionosphere, rivaled that of a solar geomagnetic storm.

Seismologists, geophysicists and oceanographers described these superlatives and other eruptions at a Dec. 12 press conference and in several presentations in Chicago at the American Geophysical Union’s fall meeting.

“These are once-in-a-lifetime observations,” said Larry Paxton, an astrophysicist at Johns Hopkins University’s Applied Physics Laboratory in Laurel, Maryland.

He and his colleagues examined data from NASA’s Global Ultraviolet Imager, on a spacecraft orbiting Earth. On the day of the eruption, Paxton said, the instrument revealed “something unusual” in the far-ultraviolet light portion of the electromagnetic spectrum: a rounded spot in satellite data coinciding with the location of the volcano where there was a temporary decrease in these UV emissions.

The instrument sees nothing in the atmosphere below about 100 kilometers above sea level, which is generally considered the limit of space. This means that some sort of material emitted – most likely water vapor from the underwater volcano – had reaches high enough in space to briefly absorb these particles of light, report the researchers. Scientists had previously estimated that the eruption had spread beyond the stratosphere and into the mesosphere. The new discovery suggests that the explosion reached even higher.

The the volcano began to erupt in December 2021 (SN: 01/21/22). By early January, he was already “one of the most prolific lightning producers” on the planet, said Chris Vagasky, a meteorologist at Vaisala Inc., an environmental instruments company headquartered in Vantaa, Finland.

Using Vaisala’s global lightning detection network, Vagasky and his colleagues estimate that on January 15 alone, there were at least 400,000 lightning strikes on and around the volcano — an order of magnitude larger than that typically seen in Earth’s most powerful supercell thunderstorms, Vagasky said. “This is the most extreme lightning event ever detected by the global grid.”

Some of the volcano’s explosive energy reached the ionosphere, the layer of Earth’s atmosphere where charged plasma coexists with other atmospheric particles. Atmospheric pressure waves from the eruption propagated into spacemoving the plasma around (SN: 08/29/22).

These plasma displacements then propagated along the Earth’s magnetic field lines, resonating through the ionosphere to disrupt plasma thousands of miles away. “It’s like plucking a guitar string,” said Claire Gasque, a space physicist at the University of California, Berkeley. (Gasque is the daughter of Scientific news‘ news director, Macon Morehouse, who was not involved in this story.)

Near the volcano, this effect on the ionosphere from the January 15 eruption rivaled, if not exceeded, the impact of a small solar geomagnetic storm that began on January 14, Gasque added. “Despite a simultaneous geomagnetic storm, the volcano dominated changes in ionospheric dynamics.”

“Most people think space weather is caused by solar influences,” Gasque said. But these data suggest that a volcano can have just as much power.

The volcano could yet break other records, the researchers said, as scientists continue to study data from the powerful explosion.

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