Earth's lightning is ignited by a potent cosmic chain reaction, according to simulations
In a groundbreaking development, scientists have unveiled a new mathematical model that simulates the conditions in a storm cloud preceding a lightning strike. The study, published in the Journal of Geophysical Research: Atmospheres on July 28, suggests that the energy for thunderstorms could be sourced from an avalanche of electrons seeded by cosmic rays.
Cosmic rays, high-energy subatomic particles primarily consisting of protons, come from various sources such as the sun, stellar explosions, and rapidly spinning neutron stars. According to the study, these cosmic rays seed an avalanche of energetic electrons in thunderclouds. These electrons, accelerated by the strong electric fields inside the clouds, collide with air molecules—primarily nitrogen and oxygen—producing further electrons and high-energy photons such as X-rays and gamma rays.
This chain reaction, captured by the Photoelectric Feedback Discharge model, explains both the initiation of lightning and associated emissions of gamma rays and X-rays observed just before lightning strikes. The electrical field needed for electrons to cascade down to Earth is around 10 times greater than the one measured inside storm clouds. The runaway chain reaction explained by the model can occur with highly variable strength, often leading to detectable levels of X-rays.
The study uses computer models to reveal that lightning strikes as a result of a powerful chain reaction that begins in outer space. This theory also accounts for observed terrestrial gamma-ray flashes that coincide with lightning events, thereby solving a longstanding mystery of how lightning begins naturally in storm clouds.
The cosmic ray theory echoes the findings of a related study titled 'Killer electrons' play pinball with space weather around Earth. Benjamin Franklin, who confirmed lightning's electrical nature in 1752 through his famous kite experiment, would undoubtedly be intrigued by these modern developments. The new model shows that electrons produced by high-speed protons accelerate along electric-field lines and multiply as they strike molecules in the atmosphere.
In essence, cosmic rays act as the initial trigger by injecting energetic electrons into the thundercloud’s electric field environment, which then multiplies through collisions and photon emissions to reach the threshold for lightning spark formation. This theory provides the first precise, quantitative explanation for how lightning initiates in nature, connecting the dots between X-rays, electric fields, and the physics of electron avalanches.
The groundbreaking model in the Journal of Geophysical Research: Atmospheres suggests that cosmic rays, which originate from sources such as the sun and rapidly spinning neutron stars, seed an avalanche of energetic electrons in thunderclouds, initiating the powerful chain reaction that leads to lightning strikes and the subsequent emission of gamma rays and X-rays.
This study not only explains the initiation of lightning but also offers a solution to the longstanding mystery of terrestrial gamma-ray flashes by demonstrating how cosmic rays act as the initial trigger for lightning formation within storm clouds, thereby connecting the dots between X-rays, electric fields, and the physics of electron avalanches.
