emirates7 - Researchers at Pennsylvania State University, led by Victor Pasko, have achieved a major scientific milestone by providing the first detailed and quantitative explanation of how lightning begins. Their groundbreaking study, published in the Journal of Geophysical Research, uncovers the powerful chain reaction that gives rise to lightning.
The research explains that strong electric fields inside thunderclouds accelerate electrons, which then collide with atmospheric molecules like nitrogen and oxygen. These collisions produce X-rays and unleash a cascade of additional electrons and high-energy photons—setting the stage for a lightning bolt.
"This is the first time we’ve been able to precisely and quantitatively explain how lightning is triggered in nature," Pasko said. "We’ve connected the roles of X-rays, electric fields, and the process of electron avalanches."
Using a mathematical model, the team analyzed a phenomenon called a terrestrial gamma-ray flash—short bursts of X-rays and radio signals generated when high-energy electrons, seeded by cosmic rays from outer space, accelerate through the electric fields of thunderstorms. The model replicates atmospheric conditions to explain the photoelectric effects seen in real-world measurements.
According to Pasko, the model shows how electrons accelerated in thunderclouds X-rays upon colliding with air molecules, leading to an electron avalanche and high-energy photon release that ultimately triggers lightning.
Doctoral student Zaid Pervez played a key role by matching the model’s results with data gathered by other researchers through ground sensors, satellites, and high-altitude aircraft. His comparison helped confirm the accuracy of the team’s explanation.
“We clarified the conditions required in thunderclouds for photoelectric reactions to occur, and how these processes generate the diverse radio signals detected before lightning strikes,” Pervez explained. He also aligned the findings with his prior research on compact intercloud discharges—lightning events confined to small regions of a cloud.
The team’s Photoelectric Feedback Discharge model, first introduced in 2023, simulates the physical environment where lightning is likely to form. The equations behind the model are available in their publication, allowing other scientists to build on their work.
Beyond explaining how lightning begins, the researchers also addressed a long-standing mystery: why some terrestrial gamma-ray flashes happen without visible lightning or strong radio signals. Pasko said their model shows that these flashes, which come from small, dense regions of a thundercloud, can produce intense X-rays with minimal light or radio emission. This is due to the rapid multiplication of electrons through the photoelectric effect, which can occur even in areas that seem dim and radio-silent.
“In these scenarios, X-rays generated by the avalanche of fast-moving electrons new seed electrons,” Pasko added. “This process can continue intensely in compact zones, explaining why gamma-ray bursts sometimes appear without typical lightning indicators.”
The research explains that strong electric fields inside thunderclouds accelerate electrons, which then collide with atmospheric molecules like nitrogen and oxygen. These collisions produce X-rays and unleash a cascade of additional electrons and high-energy photons—setting the stage for a lightning bolt.
"This is the first time we’ve been able to precisely and quantitatively explain how lightning is triggered in nature," Pasko said. "We’ve connected the roles of X-rays, electric fields, and the process of electron avalanches."
Using a mathematical model, the team analyzed a phenomenon called a terrestrial gamma-ray flash—short bursts of X-rays and radio signals generated when high-energy electrons, seeded by cosmic rays from outer space, accelerate through the electric fields of thunderstorms. The model replicates atmospheric conditions to explain the photoelectric effects seen in real-world measurements.
According to Pasko, the model shows how electrons accelerated in thunderclouds X-rays upon colliding with air molecules, leading to an electron avalanche and high-energy photon release that ultimately triggers lightning.
Doctoral student Zaid Pervez played a key role by matching the model’s results with data gathered by other researchers through ground sensors, satellites, and high-altitude aircraft. His comparison helped confirm the accuracy of the team’s explanation.
“We clarified the conditions required in thunderclouds for photoelectric reactions to occur, and how these processes generate the diverse radio signals detected before lightning strikes,” Pervez explained. He also aligned the findings with his prior research on compact intercloud discharges—lightning events confined to small regions of a cloud.
The team’s Photoelectric Feedback Discharge model, first introduced in 2023, simulates the physical environment where lightning is likely to form. The equations behind the model are available in their publication, allowing other scientists to build on their work.
Beyond explaining how lightning begins, the researchers also addressed a long-standing mystery: why some terrestrial gamma-ray flashes happen without visible lightning or strong radio signals. Pasko said their model shows that these flashes, which come from small, dense regions of a thundercloud, can produce intense X-rays with minimal light or radio emission. This is due to the rapid multiplication of electrons through the photoelectric effect, which can occur even in areas that seem dim and radio-silent.
“In these scenarios, X-rays generated by the avalanche of fast-moving electrons new seed electrons,” Pasko added. “This process can continue intensely in compact zones, explaining why gamma-ray bursts sometimes appear without typical lightning indicators.”