Researchers in South Korea have solved a long-standing mystery in plasma physics by experimentally demonstrating how tiny magnetic ripples can trigger large-scale structural changes within plasma.
The phenomenon, known as multiscale coupling, was confirmed for the first time by a research team led by Hwang Yong-Seok, PhD, a professor at the Department of Nuclear Engineering at Seoul National University (SNY).
For the study, Hwang and his team, including Park Jong-Yoon, PhD, an assistant professor at the university, and Yoon Young Dae, PhD, a theoretical physicist at the Asia Pacific Center for Theoretical Physics (APCTP), integrated fusion experiments and cosmic plasma theory.
The three scientists successfully verified that microscopic magnetic turbulence can initiate magnetic reconnection, causing a cascade of effects that reorganize plasma on a macroscopic scale.
The results represent the first experimental confirmation of multiscale coupling, and could potentially pave the way for new breakthroughs in both fusion energy and astrophysics.
From theory to reality
Multiscale coupling has long been one of the most elusive challenges in plasma physics, which represents the branch of science that studies the fourth state of matter known as plasma (a state beyond solids, liquids, and gases).
This state of matter is predominant in the universe. It powers stars and is also central to developing nuclear fusion reactors. Plasma is a superheated, ionized gas composed of positively charged atomic nuclei (ions) and free-moving electrons.
These exist at extremely high temperatures and allow atomic nuclei to overcome their mutual repulsion and fuse, releasing vast amounts of energy.
Understanding multiscale coupling in plasma has long been considered critical for both advancing fusion energy technology and potentially unraveling the origins of the universe.
Still, while theoretical models suggested that small-scale disturbances can influence the larger-scale structure of plasma, experimental confirmation had remained out of reach.
In the new experiment, the researchers injected a strong electron beam into plasma confined within a fusion device at the university. The beam induced localized turbulence and increased plasma resistivity.
This condition, in contrast, triggered magnetic reconnection, which is a process in which magnetic energy is rapidly converted into heat and motion.
Rewriting plasma physics
For the first time, the results demonstrated that a microscopic event could trigger a chain reaction leading to large-scale structural changes in plasma.
The team performed high-resolution particle simulations using the KAIROS supercomputer at the Korea Institute of Fusion Energy to verify them. The simulations closely mirrored the experimental data, which reinforced the conclusion that the team had directly observed multiscale coupling.
“This outcome was only possible through countless discussions and debates between experts in fusion and theoretical physics, who started from different interests but ultimately arrived at common ground,” Park revealed.
Park highlighted the importance of the findings, noting that they offer new clues for understanding the onset of magnetic reconnection, which is a process central to cosmic events such as solar flares and geomagnetic storms.
“We hope this research will not only expand the framework of interpretation in plasma physics but also serve as a foundation for the development of new fusion technologies,” Yoon concluded in a press release.
The study has been published in the journal Nature.