SNU–APCTP joint research team achieves first experimental proof of multiscale coupling in plasma

Microscopic turbulence in plasma can trigger macroscopic structural changes. In complex physical systems, such cross-scale interactions—between different spatial and temporal scales—are known as multiscale coupling. To the best of their knowledge, Prof. Yong-Seok Hwang’s team, together with the Asia Pacific Center for Theoretical Physics, has now experimentally proven this phenomenon for the first time. The breakthrough resolves a long-standing puzzle in plasma physics, with implications for both fusion energy development and the study of astrophysical plasmas.

Seoul National University College of Engineering announced that a joint research team led by Prof. Yong-Seok Hwang from the Department of Nuclear Engineering, in collaboration with the Asia Pacific Center for Theoretical Physics (APCTP), has experimentally demonstrated the phenomenon of multiscale coupling in plasma—a long-standing puzzle in plasma physics—through the integration of fusion experiments and astrophysical plasma theory.

Initiated under the proposal of Prof. Hwang, who holds appointments in the Department of Nuclear Engineering and the Department of Energy Systems Engineering, the study was conducted solely by three Korean researchers. The team included Dr. Jong Yoon Park, BK Assistant Professor at SNU and first author of the paper, and Dr. Young Dae Yoon, theoretical physicist at APCTP and corresponding author. This achievement, accomplished entirely by domestic researchers, is recognized as a milestone that significantly elevates Korea’s standing in global plasma science and technology research.

For plasma physicists, plasma—often called the “fourth state of matter,” distinct from solids, liquids, and gases—presents the formidable challenge of explaining how microscopic instabilities can drive macroscopic structural changes. The problem of multiscale coupling has therefore remained one of the most fundamental and long-standing issues in the field.

Plasma, however, is not only the essential medium for nuclear fusion reactions but also the predominant state of matter in the universe. Accordingly, understanding multiscale coupling in plasma has long been considered critical for both advancing fusion energy technology and unraveling the origins of the universe.

The team of Dr. Park and Dr. Yoon analyzed experimental data obtained from SNU’s fusion device and verified their findings through particle simulations using the KAIROS supercomputer at the Korea Institute of Fusion Energy. Their results proved that when microscopic magnetic turbulence is triggered, magnetic reconnection* occurs effectively, inducing macroscopic structural changes within plasma.

* Magnetic Reconnection: the process by which magnetic field energy is converted into plasma thermal energy.

The joint research team demonstrated for the first time that microscopic magnetic turbulence, deliberately induced by a strong electron beam, can increase plasma resistivity, thereby driving magnetic reconnection and ultimately producing large-scale structural changes—a direct experimental realization and proof of multiscale dynamics in plasma. The study is particularly significant as an interdisciplinary achievement, combining experimental operations of Seoul National University’s fusion device with theoretical simulations conducted at APCTP.

This achievement also reflects the sustained efforts of Seoul National University and APCTP to provide early-career researchers with opportunities at an international level and to foster interdisciplinary collaboration. It stands as a representative case of advancing the global competitiveness of domestic researchers and nurturing future leaders in science and technology.

Dr. Jong Yoon Park, BK Assistant Professor at SNU, noted, “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. It is particularly meaningful in that it offers new clues to understanding the onset of magnetic reconnection, a process that plays a key role in cosmic phenomena such as solar flares and geomagnetic storms.”

Dr. Young Dae Yoon of APCTP added, “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.”

The study was supported by the National Research Foundation of Korea, the APCTP research program, and the National Research Challenge Program. The findings were published in the international journal Nature on August 7.

□ Introduction to the SNU College of Engineering

Seoul National University (SNU) founded in 1946 is the first national university in South Korea. The College of Engineering at SNU has worked tirelessly to achieve its goal of ‘fostering leaders for global industry and society.’ In 12 departments, 323 internationally recognized full-time professors lead the development of cutting-edge technology in South Korea and serving as a driving force for international development.