Gigantic jets of lightning, 100 times stronger than normal bolts, are surging into space

• No specialized instruments study gigantic jets.
• A citizen managed to capture the event on his low-light camera.
• We now have the first 3D map of a 'gigantic jet' of lightning.

Researchers at the Georgia Tech Research Institute (GTRI) have analyzed additional data to unearth more information about the 'gigantic jet' lightning bursts that were sent towards space over Oklahoma in 2018, Phys.org has reported.

Gigantic jets can occur anywhere from 1,000 to 50,000 times every year and have often been reported in the world's tropical regions. The Oklahoma event stands out because it wasn't a part of a tropical storm. From preliminary information available about the event, the discharge is the most powerful jet recorded so far, with an estimated 300 coulombs of electrical charge that was sent toward the ionosphere, the lower edge of space. A typical lightning bolt carries less than five coulombs of charge that is either discharged to the ground or two other clouds.

The discharge also consisted of streamers of plasma at 400 degrees Fahrenheit (204 degrees Celsius). Researchers consider them relatively cool since the discharge also contains very hot structures called leaders whose temperatures exceed 8,000 degrees Fahrenheit (4,426 degrees Celsius).

How do scientists study such discharges?

Gigantic jets have been observed and studied for over two decades. However, there is no specific observing system designed to look for them. The Oklahoma event of 2018 was captured by a citizen-scientist who was operating a low-light camera in the area.

Levi Boggs, a research scientist at the GTRI, learned from a colleague that the event had been captured. This provided the researcher with additional information about the location, which was luckily found to be near a Very High Frequency (VHF) lightning mapping system as well as within the range of two Next Generation Weather Radar (NEXRAD).

After finding that the information was also accessible to instruments on satellites from the National Oceanic and Atmospheric Administration (NOAA), Boggs set up a multi-organization research team to find out more about the historic lightning bursts.

What did the research team find?

The data showed that the discharge ascended from the cloud top at altitudes of 13-18 miles (22-45 km), while optical emissions occurred at altitudes of 9-12 miles (15-20 km).

"We were able to map this gigantic jet in three dimensions with really high-quality data," said Boggs. "We were able to see very high frequency (VHF) sources above the cloud top, which had not been seen before with this level of detail. Using satellite and radar data, we were able to learn where the very hot leader portion of the discharge was located above the cloud."

Steve Cummer, a professor of electrical and computer engineering at Duke University, operates a research site where sensors deployed in an array in an open site pick up signals from locally occurring storms.

"The VHF and optical signals definitively confirmed what researchers had suspected but not yet proven: that the VHF radio from lightning is emitted by small structures called streamers that are at the very tip of the developing lightning, while the strongest electric current flows significantly behind this tip in an electrically conducting channel called a leader," said Cummer.

However, there are still a lot of unanswered questions regarding these jets, especially about why the jets shoot charge into space and not toward the ground. These events can also impact satellites in low-earth orbit as well as over-the-horizon radars.

More details about the event can be found in the journal Science Advances.

Abstract

Occasionally, lightning will exit the top of a thunderstorm and connect to the lower edge of space, forming a gigantic jet. Here, we report on observations of a negative gigantic jet that transferred an extraordinary amount of charge between the troposphere and ionosphere (∼300 C). It occurred in unusual circumstances, emerging from an area of weak convection. As the discharge ascended from the cloud top, tens of very high frequency (VHF) radio sources were detected from 22 to 45 km altitude, while simultaneous optical emissions (777.4 nm OI emitted from lightning leaders) remained near cloud top (15 to 20 km altitude). This implies that the high-altitude VHF sources were produced by streamers and the streamer discharge activity can extend all the way from near cloud top to the ionosphere. The simultaneous three-dimensional radio and optical data indicate that VHF lightning networks detect emissions from streamer corona rather than the leader channel, which has broad implications to lightning physics beyond that of gigantic jets.