Researchers at Pennsylvania State University, led by Victor Pasko, have made a major scientific breakthrough by providing the first detailed and quantitative explanation of how lightning begins. Their study, recently published in the Journal of Geophysical Research, uncovers the chain reaction that sets lightning into motion.

The team found that intense electric fields within thunderclouds can accelerate electrons to high speeds. These fast-moving electrons collide with air molecules such as nitrogen and oxygen, producing X-rays. These X-rays then trigger more electrons and high-energy photons, creating a powerful cascade that initiates lightning.

“This is the first precise and quantitative model that explains lightning initiation in nature,” Pasko said. “It links X-rays, thundercloud electric fields, and electron avalanche physics.”

Using advanced mathematical models, the researchers replicated atmospheric conditions to match real-world observations. Their simulations confirmed that electrons, initially seeded by cosmic rays from space, gain energy in thunderstorm electric fields and emit bursts of high-energy photons. This natural event, called a terrestrial gamma-ray flash (TGF), is an invisible burst of X-rays and radio waves originating in the atmosphere.

“Our model accurately simulates conditions that match what field researchers have observed,” Pasko explained. “We showed how thunderclouds can accelerate electrons enough to produce X-rays, which in turn generate more electrons and high-energy photons—setting off the lightning process.”

Doctoral student Zaid Pervez applied the model to compare simulation results with existing data gathered from satellites, high-altitude aircraft, and ground sensors. This allowed the team to pinpoint what conditions inside clouds lead to lightning and explain the varied radio signals that appear before a strike.

“To validate our findings, I compared the model with previous research and my own work on compact intercloud discharges—small, localized lightning events inside clouds,” Pervez said.

The researchers developed a model in 2023 called the Photoelectric Feedback Discharge, which simulates the physical conditions under which lightning is likely to begin. They also made the model’s equations publicly available for use by other scientists.

Besides clarifying how lightning starts, the study also explains why TGFs often occur without the typical light flashes and radio signals associated with lightning. According to Pasko, the intense X-rays generated in these electron avalanches can produce new electrons via the photoelectric effect in air, amplifying the avalanches rapidly. These reactions can happen in small, concentrated areas and with varying intensities, sometimes leading to detectable X-rays without any visible or audible lightning—helping explain the mysterious “silent” gamma-ray bursts in storms.

 

 

For any quarries contact us