Penn State Scientists Generate Lightning-Like Discharges in Common Lab Materials
New research led by scientists at Penn State indicates that lightning-like electrical discharges can be generated within common insulating materials in a laboratory setting. This discovery, detailed in a paper in Physical Review Letters, suggests that conditions typically found in storm clouds can be replicated on a much smaller scale.
"The calculations showed that when a high-powered electron source is supplied, lightning-like discharges can be triggered in materials such as glass, acrylic, and quartz."
Victor Pasko, a professor of electrical engineering at Penn State and lead author, stated that the research applied models used for lightning studies to a reduced scale, comparable to a deck of cards.
Methodology and Findings
The team utilized detailed numerical simulations to demonstrate that radiation bursts resembling lightning could form within small solid blocks under laboratory-achievable conditions. This process, termed a photoelectric feedback discharge, offers new avenues for investigating lightning physics under controlled environments, including its initiation and propagation.
Pasko noted that the team modeled similar phenomena in a material 1,000 times denser than air, with discharges occurring 1,000 times faster than in thunderclouds—within one-billionth of a second. While thunderstorms typically produce electric potentials of about 100 million volts over kilometer-scale regions, dense solid materials were found to mimic these electric conditions over just a few centimeters.
Materials like acrylic, quartz, and bismuth germanate (a crystal used in X-ray detection) are approximately 1,000 times denser than air. Their density, combined with charge buildup from an energetic beam, could theoretically allow these materials to reach lightning-like electrical potentials in a small space. The researchers propose that these conditions can trigger the same photoelectric feedback loop previously thought to occur exclusively in thunderstorms.
Underlying Physics
Lightning in nature typically forms from electrical charge imbalances in Earth's atmosphere or between the atmosphere and the Earth's surface. Electrons move through a storm's electric field, colliding with nitrogen and oxygen atoms, leading to blasts of gamma rays. These bursts, when triggered by lightning, are called terrestrial gamma-ray flashes, capable of sending radiation hundreds of miles into space.
The research team previously identified that emissions such as X-rays and radio waves result from accelerated electrons colliding with air molecules in thunderclouds. The resulting energy, in the form of an electron avalanche, initiates lightning. This phenomenon, known as a relativistic runaway electron avalanche, is central to the theoretical work. Under strong electric fields, electrons can accelerate rapidly, gaining high energy and emitting X-rays and gamma rays as they decelerate in surrounding material.
In thunderstorms, these runaway electrons create a chain reaction: they collide with air molecules, producing high-energy photons that bounce backward and dislodge more energetic electrons. The study modeled conditions in common materials that could trigger this same runaway photoelectric feedback loop.
Implications
Studying lightning-like conditions in a desktop setting under controlled conditions could provide a more cost-effective approach to answering questions about lightning formation. This increased understanding could benefit fields such as meteorology. Current methods for studying lightning in clouds involve large-scale experiments, often requiring balloons, aircraft, or rockets to observe thunderclouds.
This research was partially inspired by a recent study where discharges resembling lightning were observed to propagate in a small volume of specific materials. Pasko aimed to develop a mathematical model to describe and replicate the photoelectric feedback loop in miniature desktop conditions using dense materials.
Other authors involved in the paper include Sebastien Celestin from the University of Orléans, France, and Anne Bourdon from École Polytechnique, France, and The French National Center for Scientific Research. The U.S. National Science Foundation provided funding for the Penn State aspects of this research.