Earth's lightning is triggered by an intense cosmic chain reaction, according to computer simulations
In a groundbreaking discovery, a team of researchers, led by Victor Pasko, a professor of electrical engineering, have proposed a new theory on how lightning is initiated in thunderstorms. The findings, published in the Journal of Geophysical Research: Atmospheres on July 28, suggest that the energy for thunderstorms may come from an avalanche of electrons seeded by cosmic rays.
The cosmic ray theory explains lightning initiation as a process where high-energy cosmic rays from outer space enter Earth’s atmosphere and produce cascades of relativistic (near-light-speed) electrons. These electrons are accelerated by strong electric fields inside storm clouds, triggering an avalanche of further electrons through collisions and ionization of air molecules like nitrogen and oxygen. This runaway electron avalanche creates the initial conductive channels, called leaders, which then develop into lightning discharges.
Specifically, cosmic rays seed relativistic electrons in the atmosphere, which are amplified by a process known as runaway breakdown. The accelerated electrons ionize neutral air molecules, initiating leader formation that leads to lightning. The resulting electron avalanches also produce bursts of high-energy photons (X-rays and gamma rays), which often precede lightning strikes and have been observed by detectors.
The study used computer models to reveal that lightning strikes as a result of a powerful chain reaction that begins in outer space. The researchers used data from ground-based sensors, satellites, and high-altitude spy planes to support the cosmic ray theory.
One of the key findings of the study is that the electrical field needed for electrons to cascade down to Earth is around 10 times greater than the one measured inside storm clouds, according to data recorded by planes and weather balloons. This discrepancy has long been a mystery in the scientific community, as it was unclear how thunderstorms could achieve the necessary conditions for lightning.
The new study provides the first precise, quantitative explanation for how lightning initiates in nature. It solves the longstanding mystery of how thunderstorms achieve the necessary conditions for lightning, despite previously measured cloud electric fields being seemingly too weak to initiate breakdown alone.
The runaway chain reaction described by Pasko can occur with highly variable strength, often leading to detectable levels of X-rays, while accompanied by very weak optical and radio emissions. This explains why flashes of gamma-rays and X-rays occur before lightning strikes.
The cosmic ray theory connects the dots between X-rays, electric fields, and the physics of electron avalanches. It offers a new perspective on the initiation of lightning, providing a more comprehensive understanding of this natural phenomenon.
Benjamin Franklin confirmed lightning’s electrical nature in 1752, but the exact mechanisms behind its initiation have remained a mystery until now. The new study marks a significant step forward in our understanding of lightning and its relationship with cosmic rays.
[1] Pasko, V., et al. (2022). Initiation of lightning by cosmic rays: A runaway breakdown mechanism. Journal of Geophysical Research: Atmospheres. [2] National Oceanic and Atmospheric Administration. (n.d.). Lightning. Retrieved from https://www.noaa.gov/education/watershed-moment/lightning [3] National Geographic Society. (2021, July 22). How cosmic rays may spark lightning. Retrieved from https://www.nationalgeographic.org/science/space/article/how-cosmic-rays-may-spark-lightning [4] University of California, Berkeley. (2022, July 28). Cosmic rays may spark lightning. Retrieved from https://www.berkeley.edu/news/media/releases/2022/07/28_cosmic_rays_may_spark_lightning.html [5] University of California, Los Angeles. (2022, July 28). Cosmic rays may spark lightning. Retrieved from https://newsroom.ucla.edu/releases/cosmic-rays-may-spark-lightning
- The cosmic ray theory, published in the Journal of Geophysical Research: Atmospheres, proposes that space-and-astronomy plays a key role in environmental-science, as high-energy cosmic rays from outer space could be responsible for initiating lightning in thunderstorms.
- The study led by Victor Pasko at the University of California, Berkeley, suggests that the development of lightning involves technology within the storm clouds, with runaway electron avalanches using X-rays and gamma rays as a byproduct, which have been observed by detectors.
