Lightning "jet giant" is a puzzle.  These researchers solve it.

Lightning “jet giant” is a puzzle. These researchers solve it.

How

Ordinary enough lightning can start, but researchers are revealing the secrets behind a rare type of electrical discharge called “giant jets.” These are extraordinary bursts of light from the top of the clouds that can rise to the edge of space.

Only five observations of these aircraft are made on average in a year, usually by chance. Sometimes lucky photographers capture them in long-exposure photos, and occasionally they are spotted by weather satellites.

A study published Wednesday in the journal Science Advances sheds light on the structure and cause of giant aircraft. It analyzed a jet launched in Oklahoma on May 14, 2018, which soared 50 miles above a storm cloud and distributed the charge of more than 100 conventional lightning bolts. It was the most powerful giant aircraft ever studied.

The researchers mapped the plane in 3D and identified structural features in greater detail than ever before.

Elusive red sprites, like glowing jellyfish in the night sky, photographed in Oklahoma

The investigation was inspired when Levi Boggs, a research scientist at the Georgia Institute of Technology and one of the paper’s lead authors, learned about a photo of an Oklahoma jetliner by a citizen scientist.

“Kevin Balevik [the photographer] He has a l0w-light camera in central Texas that he turns on at random sometimes, and he took that camera a couple of years ago,” Boggs said. The photo was “sort of sitting. I was told about it and decided to investigate a bit.”

That’s when Boggs assembled a team that reviewed satellite, radar and radio wave data to reconstruct what had happened.

The researchers have been able to develop a model of the aircraft in 3D since it was seen by two satellite-based optical lightning devices, including the Lightning Mapping Array on the GOES-15 weather satellite overlooking the eastern United States.

“I think it caused the emptying of an area of ​​about 50 kilometers by 50 kilometers inside the cloud,” Boggs said. “It carried that charge into the ionosphere,” the layer of the atmosphere 50 to 400 miles above the Earth’s surface.

Steve Comer, a professor of electrical and computer engineering at Duke University, was able to extract high-frequency electromagnetic data from a series of nearby antennas near the storm. For the first time, he was able to confirm that the high-frequency signal emitted by lightning could in fact be traced back to tiny tendril-like electric “washers” at the tip of the spreading lightning channel.

Ground lightning detection networks were also useful in the investigation of the aircraft, as they reported the storm’s lightning rates prior to launch.

“We were able to determine the peak currents and the type of discharge for the parent storm,” Boggs said.

Oddly enough, Boggs said, there were no conventional lightning strikes in the immediate area that produced the giant plane. He has a theory about this tied to the most common location of aircraft: over the ocean instead of on the ground.

Thunderstorms typically exhibit a three-polar electric field, which means that they consist of a positively charged region near the ground, a negatively charged region near the bottom of the cloud and a positively charged region near the top of the cloud. The contrast between the negative charge at the bottom of the cloud and the positive charge near the ground causes lightning.

“What happens is that there is a funnel of these cloud-to-ground discharges,” Boggs said.

Suppression of cloud-to-ground strikes occurs more frequently with ocean storms, for reasons scientists still don’t understand, Boggs said.

The researchers found that in the absence of a charge contrast between the cloud and the surface, negative charge accumulates in the clouds. And giant planes can relieve excess negative charge.

Some of the most intense episodes of giant jets are observed over tropical storms or hurricanes – which are notorious for being devoid of ordinary lightning. in August. 11 and 12, 2015, Hurricane Hilda spawned a barrage of giant aircraft as it skidded southeast of Hawaii.

There is still a lot that remains undiscovered and unknown in the field of giant aircraft, which fall under the umbrella of TLEs, or transient flare events – that is, overhead lightning.

“We still don’t really know how often it happens,” Boggs said. “There are about five discoveries of giant aircraft every year, but we hope to have tens of thousands.”

To do this, Boggs and his team are working on a machine learning algorithm to integrate into geostationary lightning plot data.

“We just didn’t see them because the observations are very limited,” Boggs said. “It’s really hard to coordinate with instruments in orbit, so we have [National Science Foundation] Granted that this will come soon. will mainly use [satellite data] To search for these giant planes in huge quantities… I hope we can detect these things across the hemisphere and hopefully 24 hours a day.”

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