That phenomenon, known as corona discharge, involves tiny bursts of electricity forming at the tips of leaves. These faint electrical pulses can cause treetops to emit a subtle glow in the ultraviolet (UV) range. Scientists have suspected for more than 70 years that forests might produce these effects during storms due to unusual electric field activity, but direct evidence in nature had remained elusive.

A Long-Standing Mystery Finally Tested in the Field

The research team included William Brune, a distinguished professor of meteorology and atmospheric science; Patrick McFarland, a doctoral student in the same field; Jena Jenkins, an assistant research professor; and David Miller, a former associate research professor now working at the Penn State Applied Research Lab. Their objective was to document corona discharges occurring naturally for the first time.

Florida was chosen because of its frequent thunderstorms, which seemed ideal for the study. However, the weather did not cooperate as expected. For three weeks, McFarland and Brune followed short-lived storms that dissipated quickly, leaving them without useful data.

Breakthrough Observation in North Carolina

As the team began heading back to Pennsylvania, conditions changed. Large, long-lasting storms developed just west of Interstate 95. Seizing the opportunity, the researchers stopped at the University of North Carolina at Pembroke and set up their equipment in a parking lot. They aimed their instruments at the upper branches of a sweetgum tree located about 100 feet from their van.

A thunderstorm persisted for nearly two hours, bringing heavy rain and frequent lightning. During this time, the team recorded corona discharges on the sweetgum tree and also observed similar activity on a nearby long needle loblolly pine as the storm weakened. These observations marked the first confirmed detection of corona discharges in a natural setting. The findings were later published in Geophysical Research Letters.

“This just goes to show that there’s still discovery science being done,” said McFarland, lead author on the paper. “For more than half a century, scientists have theorized that corona exists, but this proves it.”

How Corona Discharges Form in Storms

According to the researchers, corona discharges occur because of strong electrical imbalances during storms. Thunderclouds develop large negative charges that attract positive charges on the ground. This positive charge travels upward through trees, concentrating at the highest points such as leaf tips.

At these tiny, hair-like structures, the electric field becomes intense enough to produce a faint glow that can be seen in both visible light and UV. The UV radiation generated by this process can break apart water vapor molecules, leading to the formation of hydroxyl.

Atmospheric Chemistry and Air Cleaning Effects

Hydroxyl plays a key role in the atmosphere as its primary oxidizer. Oxidizers help remove pollutants by reacting with airborne chemicals and transforming them into substances that are easier to eliminate. These reactions involve compounds released by trees as well as human-generated pollutants, including methane, a potent greenhouse gas.

Earlier work by the team showed that corona discharges could be a significant source of these atmospheric cleansing agents within forest canopies. This makes the phenomenon potentially important for air quality and climate processes.

Laboratory Insights and Field Confirmation

The researchers had previously studied this effect in controlled experiments. By applying high-voltage, low-current electrical pulses to tree branches, they found a strong link between UV emissions from corona discharges and the production of hydroxyl. In both those experiments and the recent field observations, they also noted minor damage to leaves at the points where corona formed.

To observe the phenomenon outdoors, the team created the Corona Observing Telescope System. This instrument is a Newtonian telescope connected to a UV-sensitive camera. It includes geolocation capabilities, sensors to measure atmospheric electricity, and calibration using a mercury lamp. The system blocks solar UV wavelengths so that only corona, lightning and fire can produce detectable signals.

Hundreds of Corona Events Captured

Using this system in North Carolina, the team recorded 859 corona events on the sweetgum tree and 93 on the loblolly pine. Each event lasted anywhere from a fraction of a second to several seconds, according to McFarland. Additional observations were made during four other thunderstorms and across four different tree species.

“It’s nearly invisible to the naked eye but our instruments give rise to a vision of swaths of scintillating corona glowing as thunderstorms pass overhead,” McFarland said. “Such widespread coronae have implications for the removal of hydrocarbons emitted by trees, subtle tree leaf damage and could have broader implications for the health of trees, forests and the atmosphere.”

Open Questions About Trees and the Environment

Although the team has confirmed that corona discharges occur in nature, many questions remain. Researchers want to know whether these electrical events harm trees or provide some benefit. They are also investigating whether trees have adapted to tolerate or even take advantage of this process, and whether the resulting atmospheric cleansing benefits forest ecosystems.

To explore these questions, the scientists are beginning collaborations with tree ecologists and biologists. Their work could lead to new insights into how forests interact with the atmosphere and how these interactions influence environmental health.

The study was supported by the U.S. National Science Foundation, with Brune, Jenkins and Miller serving as co-authors.

Their study, published in Nature Communications, suggests that carbon hydride could take on an unusual quasi-one-dimensional superionic state under the intense pressures and temperatures found far beneath the surfaces of these distant planets.

Why Planetary Interiors Matter

More than 6,000 exoplanets have been discovered so far, and that number continues to grow. To better understand how planets form and evolve, researchers from astronomy, planetary science, and Earth science are increasingly working together. By combining observations, experiments, and theoretical models, they aim to uncover the physical processes that shape planets, including how magnetic fields are generated.

This growing interest also extends to the hidden layers within planets and moons in our own Solar System. Studying what happens deep below the surface can provide clues about planetary behavior and even help scientists assess whether distant worlds could support life.

“Hot Ice” Layers Inside Ice Giants

Data on the densities of Uranus and Neptune indicate that these planets contain unusual internal layers often described as “hot ices.” These regions sit beneath outer atmospheres of hydrogen and helium and above solid cores.

Scientists believe these layers are made up of water (H₂O), methane (CH₄), and ammonia (NH₄). However, the extreme conditions in these environments likely force these familiar compounds into exotic and unfamiliar forms.

Simulating Extreme Planetary Conditions

The intense pressures and temperatures inside ice giants can produce states of matter that do not exist on Earth. To explore this, Liu and Cohen used high-performance computing and machine-learning tools to run detailed quantum simulations of carbon hydride (CH).

They modeled conditions ranging from nearly 5 million to nearly 30 million times Earth’s atmospheric pressure (500 to 3,000 gigapascals) and temperatures between 6,740 and 10,340 degrees Fahrenheit (4,000 to 6,000 Kelvin).

A Strange “Spiral” Superionic State

The simulations revealed a striking structure. Carbon atoms form an ordered hexagonal framework, while hydrogen atoms move through it along spiral-like paths. This creates a quasi-one-dimensional superionic state.

Superionic materials are unusual because they behave partly like solids and partly like liquids. One type of atom remains locked in place within a crystal structure, while another type moves freely through it.

“This newly predicted carbon-hydrogen phase is particularly striking because the atomic motion is not fully three-dimensional,” Cohen explained. “Instead, hydrogen moves preferentially along well-defined helical pathways embedded within an ordered carbon structure.”

Implications for Heat, Electricity, and Magnetic Fields

The directional movement of hydrogen atoms could have major effects on how energy flows inside planets. It may influence how heat and electricity are transported through these deep layers.

These properties are especially important for understanding how Uranus and Neptune generate their magnetic fields, which differ in unusual ways from those of other planets.

Broader Impact Beyond Planetary Science

The findings also highlight how simple elements can behave in surprisingly complex ways under extreme conditions. Even basic compounds like carbon and hydrogen can form highly organized and unexpected structures.

“Carbon and hydrogen are among the most abundant elements in planetary materials, yet their combined behavior at giant-planet conditions remains far from fully understood,” Liu concluded.

Beyond helping scientists understand distant planets, this research could also inform advances in materials science and engineering by revealing new types of directional behavior in matter.

“In the fields of physics, chemistry, biology and materials science, many important phenomena happen incredibly fast,” said research team leader Yunhua Yao from East China Normal University. “Our new technique can capture the complete evolution of both the brightness and internal structure of an object in a single measurement. This is a big step forward for understanding the fundamental nature of matter, designing new materials and even uncovering the mysteries of biological processes.”

The team described their method in Optica, Optica Publishing Group’s journal for high-impact research. The technique is known as compressed spectral-temporal coherent modulation femtosecond imaging (CST-CMFI). Using this system, the researchers were able to track ultrafast activity such as plasma forming in water after a femtosecond laser pulse and the behavior of excited charge carriers in ZnSe.

“Beyond helping scientists study materials that change instantly in response to laser light, chemical reactions that rearrange atoms at lightning speed and the dynamic behavior of biomolecules over incredibly short timescales, CST-CMFI could help improve high-power laser technologies used for clean energy research, advanced manufacturing and scientific instrumentation,” said Yao. “It might also lead to the development of more efficient electronics, improved solar cells and faster devices by enabling a better understanding of how materials behave at extremely fast timescales.”

Capturing More Than Brightness in Ultrafast Imaging

This work is part of ongoing efforts at the Extreme Optical Imaging Laboratory at East China Normal University to advance ultrafast camera technologies. A key focus is single-shot ultrafast optical imaging, which captures events that cannot be repeated by recording everything in a single exposure, similar to snapping a single frame that contains an entire sequence.

In the past, these techniques mainly recorded changes in brightness, also known as light intensity. However, light also carries phase information, which reveals how it bends or changes speed as it passes through materials. The researchers set out to capture both intensity and phase at the same time, providing a more complete picture of ultrafast processes.

To achieve this, they combined time-spectrum mapping, compressive spectral imaging and coherent modulation imaging. Each method contributes a specific advantage, including the ability to follow extremely fast changes, gather more data in one measurement and preserve fine image details.

How the CST-CMFI Technique Works

The system uses a chirped laser pulse made up of multiple wavelengths that arrive at slightly different times. This setup effectively links time to wavelength. When the pulse interacts with a fast-changing event, the scattered light carries detailed spatial, spectral and phase information. This information is then compressed into a single image through dispersion-encoded coherent modulation imaging.

A physics-informed neural network processes this data by separating the wavelengths and reconstructing both intensity and phase over time. Since each wavelength represents a specific moment, the result is a sequence of frames that forms an ultrafast movie captured in a single shot.

Real-Time Views of Plasma and Electron Behavior

To test the technique, the researchers examined two types of ultrafast phenomena. One experiment focused on plasma created in water by a femtosecond laser. Understanding how this plasma forms and evolves could support applications such as laser-based medical procedures. The imaging results revealed both brightness and phase changes within the plasma channel, including the formation of a dense free-electron plasma that affects how light is absorbed and how it travels through water.

The team also studied carrier dynamics in ZnSe to better understand how electrical charges move after being excited by light. Insights like these are important for improving optical and electronic devices made from this material, potentially leading to faster and more efficient technologies.

“Using CST-CMFI, we were able to see phase variations associated with the carrier dynamics, even when there were no significant changes in intensity,” said Yao. “This highlights a key advantage of our method: Phase measurements can be much more sensitive than intensity measurements in detecting subtle ultrafast processes.”

Expanding Applications and Future Improvements

Looking ahead, the researchers plan to apply the method to study additional phenomena, including interface dynamics and ultrafast phase transitions. These areas require detecting extremely small changes in the phase of light, making the new technique especially valuable.

At present, CST-CMFI converts spectral information into temporal information, which limits its ability to study processes that are highly sensitive to spectral changes. To address this, the team aims to combine CST-CMFI with compressive ultrafast photography. This next step would allow spectral and temporal information to be captured separately, significantly expanding the range of applications and improving the overall versatility of the technology.