A detailed 3-D study of a massive electric discharge that soared 50 miles into space above a thunderstorm in Oklahoma has provided new information about an elusive atmospheric phenomenon known as giant jets. The Oklahoma discharge was the most powerful giant jet studied to date, carrying an electrical charge of 100 times the charge of a typical thunderstorm bolt.
The giant plane transferred an estimated 300 coulombs of electric charge to the ionosphere – the lower edge of space – from the thunderstorm. Typical lightning bolts carry less than five coulombs between the cloud and the ground or within the clouds. The upward discharge included a relatively cool stream (about 400 degrees Fahrenheit) of plasma, as well as structures called leaders that are extremely hot – over 8000 degrees Fahrenheit.
“We were able to map this giant plane in three dimensions with really high-quality data,” said Levi Boggs, a research scientist at Georgia Technical Research Institute (GTRI) and corresponding author of the research paper. “We were able to see high-frequency (VHF) sources above the top of the cloud, which had never been seen before in this level of detail. Using satellite and radar data, we were able to see where the very leading portion of the discharge was located above the cloud.”
Boggs has worked with a multi-organizational research team, including the Universities Space Research Consortium (USRA), Texas Tech University, University of New Hampshire, Politecnica de Catalunya, Duke University, University of Oklahoma, and the National Oceanic and Atmospheric Administration’s (NOAA) National Severe Storm Laboratory. and Los Alamos National Laboratory. The search was reported in August. 3 inch science progress.
Steve Comer, professor of electrical and computer engineering at Duke University, uses electromagnetic waves emitted by lightning to study the powerful phenomenon. He runs a research site where sensors resembling conventional antennas are arranged in an otherwise empty field, waiting to pick up signals from locally occurring storms.
“The optical and VHF signals conclusively confirmed what the researchers suspected but not yet proven: that the VHF radio of lightning emits from tiny structures called streamers at the top of the developing lightning, while the significantly stronger electric current flows beyond this.” Advice in An electrically conductive conduit is called the conductor,” Comer said.
Doug Mash, co-author of the research paper at the Universities Space Research Consortium (USRA), said the study was unique in determining that the 3D locations of lightning optical emissions were much higher than cloud tops.
Radio map sources extending from the storm’s thermal structure. The gray level represents the top of the storm. Credits: science progress (2022). DOI: 10.1126 / sciadv.abl8731
“The fact that the giant plane was detected by several systems, including the Lightning Mapping Array and two geostationary optical lightning devices, was a unique event and gives us a lot of information about the giant planes,” said Match. “Importantly, this is probably the first time a giant 3D jet has been drawn over clouds using the geostationary Lightning Mapper (GLM) toolkit.”
Giant planes have been observed and studied over the past two decades, but since there is no specific monitoring system to look for them, discoveries have been scarce. Boggs learned of the Oklahoma event from a colleague, who told him about a giant jet plane that had been photographed by a citizen scientist working with a low-light camera on May 14, 2018.
Fortunately, the event occurred in a location close to the VHF Lightning Mapping System, within the range of two Next Generation Weather Radar (NEXRAD) locations and could be accessed by on-satellite instruments from the NOAA Network of Geostationary Operational Environmental Satellite (GOES) . Boggs decided that data from those systems was available and worked with colleagues to piece it together for analysis.
“The detailed data showed that these cold streams start spreading just above the top of the cloud,” Boggs explained. “They spread all the way into the lower ionosphere at 50-60 miles altitude, making a direct electrical connection between the top of the cloud and the lower ionosphere, which is the lower edge of space.”
This connection transmits thousands of amperes of current in about a second. The upward discharge moved the negative charge from the cloud into the ionosphere, typical of giant aircraft.
The data showed that as the discharge rose from the top of the cloud, VHF radio sources were detected at altitudes of 22 to 45 kilometers (13 to 28 miles), while light emissions from lightning leaders remained near the top of the cloud at an altitude of 15 to 20 kilometers (9 to 12 miles). Simultaneous 3D radio and optical data indicate that VHF lightning networks detect emissions from the flowing corona rather than the leading channel, which has broad implications for lightning physics beyond those of giant aircraft.
Why do giant planes launch a charge into space? The researchers speculate that something might be blocking the flow of charge downward — or toward other clouds. Oklahoma event records show little lightning activity from the storm before the record-breaking giant jet was launched.
“For whatever reason, there is usually a suppression of cloud-to-ground discharges,” Boggs said. “There is a buildup of negative charge, and then we think conditions at the top of the storm are weakening the upper charge layer, which is usually positive. In the absence of the lightning discharges that we usually see, the giant jet might mitigate the buildup of excess negative charge in the cloud.”
At the moment, there are a lot of unanswered questions about giant planes, which are part of the category of transient luminous mysterious events. That’s because observations of them are rare and happen by chance – from pilots or airline passengers who happen to see them, or ground observers operating night-scanning cameras.
Estimates of the frequency of megaplanes range from 1,000 per year to 50,000 per year. It is often reported in tropical regions of the world. However, Oklahoma’s giant jet—which was twice as powerful as the next most powerful—was not part of the Tropical Storm system.
In addition to their novelty, giant aircraft could have an impact on the operation of satellites in low Earth orbit, Boggs said. And as more of these spacecraft are launched, signal degradation and performance issues could become more significant. Giant aircraft can also affect technologies such as trans-horizon radars that bounce radio waves off the ionosphere.
Boggs belongs to the Severe Storm Research Center, which was set up at GTRI to develop improved technologies for warning of severe storms, such as tornadoes, common in Georgia. Work on giant planes and other atmospheric phenomena is part of this effort.
How does positive cloud-to-ground lightning strike far from its source?
Levi D. Boggs et al, The upward propagation of giant planes detected by 3D radio and optical mapping, science progress (2022). DOI: 10.1126 / sciadv.abl8731
Provided by Georgia Institute of Technology
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