By Dr. Tim Sandle
August 2, 2025
DIGITAL JOURNAL
The crater of Mount Ruang flamed with lava against a backdrop of lightning bolts overnight after erupting five times - Copyright AFP/File Kena Betancur
For all the advances in our understanding of weather, one area has remained elusive: how does lightning begin? Scientists have been examining how lightning begins inside thunderclouds. These findings offer the first quantitative, physics-based explanation for lightning initiation. This outcome offers a glimpse into the stormy heart of Earth’s atmosphere.
It is known that lightning begins as static charges in a rain cloud. Winds inside the cloud are very turbulent, and water droplets in the bottom part of the cloud are caught in the updrafts and lifted to great heights where the much colder atmosphere freezes them. At the same time, downdrafts in the cloud push ice and hail down from the top of the cloud.
But what is the actual trigger? The explanation concerns the spectacular naturally occurring bursts of X-rays and accompanying radio emissions that are observed in association with lightning activity in the Earth’s atmosphere.
With the study, scientists describe how they determined strong electric fields in thunderclouds accelerate electrons that crash into molecules like nitrogen and oxygen, producing X-rays and initiating a deluge of additional electrons and high-energy photons. This represents ‘the perfect storm’ from which lightning bolts are born.
The crater of Mount Ruang flamed with lava against a backdrop of lightning bolts overnight after erupting five times - Copyright AFP/File Kena Betancur
For all the advances in our understanding of weather, one area has remained elusive: how does lightning begin? Scientists have been examining how lightning begins inside thunderclouds. These findings offer the first quantitative, physics-based explanation for lightning initiation. This outcome offers a glimpse into the stormy heart of Earth’s atmosphere.
It is known that lightning begins as static charges in a rain cloud. Winds inside the cloud are very turbulent, and water droplets in the bottom part of the cloud are caught in the updrafts and lifted to great heights where the much colder atmosphere freezes them. At the same time, downdrafts in the cloud push ice and hail down from the top of the cloud.
But what is the actual trigger? The explanation concerns the spectacular naturally occurring bursts of X-rays and accompanying radio emissions that are observed in association with lightning activity in the Earth’s atmosphere.
With the study, scientists describe how they determined strong electric fields in thunderclouds accelerate electrons that crash into molecules like nitrogen and oxygen, producing X-rays and initiating a deluge of additional electrons and high-energy photons. This represents ‘the perfect storm’ from which lightning bolts are born.
‘Lightning is a major hazard that claims many lives every year,’ the UN’s World Meteorological Organization says – Copyright AFP Sergei SUPINSKY
The scientists used mathematical modelling to explain field observations of photoelectric phenomena in Earth’s atmosphere — when relativistic energy electrons, which are seeded by cosmic rays entering the atmosphere from outer space, multiply in thunderstorm electric fields and emit brief high-energy photon bursts.
This phenomenon, known as a terrestrial gamma-ray flash (also known as dark lightning), comprises the invisible, naturally occurring bursts of X-rays and accompanying radio emissions. These flashes been recorded to last 0.2 to 3.5 milliseconds, and have energies of up to 20 million electronvolts. It is speculated that the phenomena are caused by intense electric fields produced above or inside thunderstorms
According to lead researcher Victor Pasko, professor of electrical engineering in the Penn State School of Electrical Engineering and Computer Science: “Our findings provide the first precise, quantitative explanation for how lightning initiates in nature…”It connects the dots between X-rays, electric fields and the physics of electron avalanches.”
“By simulating conditions with our model that replicated the conditions observed in the field, we offered a complete explanation for the X-rays and radio emissions that are present within thunderclouds,” Pasko adds. “We demonstrated how electrons, accelerated by strong electric fields in thunderclouds, produce X-rays as they collide with air molecules like nitrogen and oxygen, and create an avalanche of electrons that produce high-energy photons that initiate lightning.”
The research appears in the Journal of Geophysical Research: Atmospheres, titled “Photoelectric Effect in Air Explains Lightning Initiation and Terrestrial Gamma Ray Flashes.”
Megaflash
In related news, a 515-mile lightning bolt has lit up the skies from Texas to Kansas City, breaking previous records and reshaping our understanding of extreme weather. Scientists have begun studying the mechanics of “megaflash” lightning. These are rare, colossal discharges that span hundreds of miles across the sky. The massive bolts, emerging from long-lived, sprawling thunderstorms, pose real danger to humanity even when skies seem clear.
Most lightning flashes are limited to less than 10 miles in reach. When a lightning bolt reaches beyond 60 miles (100 kilometers to be exact), it is considered a megaflash. Less than 1 percent of thunderstorms produce megaflash lightning. Even within this narrow band of corruence, a 500 mile plus expanse of lightning remains truly remarkable.
The scientists used mathematical modelling to explain field observations of photoelectric phenomena in Earth’s atmosphere — when relativistic energy electrons, which are seeded by cosmic rays entering the atmosphere from outer space, multiply in thunderstorm electric fields and emit brief high-energy photon bursts.
This phenomenon, known as a terrestrial gamma-ray flash (also known as dark lightning), comprises the invisible, naturally occurring bursts of X-rays and accompanying radio emissions. These flashes been recorded to last 0.2 to 3.5 milliseconds, and have energies of up to 20 million electronvolts. It is speculated that the phenomena are caused by intense electric fields produced above or inside thunderstorms
According to lead researcher Victor Pasko, professor of electrical engineering in the Penn State School of Electrical Engineering and Computer Science: “Our findings provide the first precise, quantitative explanation for how lightning initiates in nature…”It connects the dots between X-rays, electric fields and the physics of electron avalanches.”
“By simulating conditions with our model that replicated the conditions observed in the field, we offered a complete explanation for the X-rays and radio emissions that are present within thunderclouds,” Pasko adds. “We demonstrated how electrons, accelerated by strong electric fields in thunderclouds, produce X-rays as they collide with air molecules like nitrogen and oxygen, and create an avalanche of electrons that produce high-energy photons that initiate lightning.”
The research appears in the Journal of Geophysical Research: Atmospheres, titled “Photoelectric Effect in Air Explains Lightning Initiation and Terrestrial Gamma Ray Flashes.”
Megaflash
In related news, a 515-mile lightning bolt has lit up the skies from Texas to Kansas City, breaking previous records and reshaping our understanding of extreme weather. Scientists have begun studying the mechanics of “megaflash” lightning. These are rare, colossal discharges that span hundreds of miles across the sky. The massive bolts, emerging from long-lived, sprawling thunderstorms, pose real danger to humanity even when skies seem clear.
Most lightning flashes are limited to less than 10 miles in reach. When a lightning bolt reaches beyond 60 miles (100 kilometers to be exact), it is considered a megaflash. Less than 1 percent of thunderstorms produce megaflash lightning. Even within this narrow band of corruence, a 500 mile plus expanse of lightning remains truly remarkable.
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