Turbulence is ubiquitous and occurs every day, such as when milk is stirred into coffee or in the stormy motions of the ocean and the atmosphere. Media in space and astrophysical systems can also develop turbulence, but the physics is different because the medium is in an ionized state (known as the plasma state) and the flow motion is strongly coupled to electromagnetic fields. Furthermore, space plasma is collisionless because the medium is so dilute that the particles do not collide with each other.
How does plasma develop into turbulence? How is the fluctuation energy distributed in collisionless turbulence? Turbulence in space plasma remains a mystery in physics.
An international research team from the Technische Universität Braunschweig and the University of Tokyo, in cooperation with Tohoku University, Kyushu University, Osaka University and multinational research institutes, has demonstrated, for the first time, a reversal phenomenon of magnetic field rotation in space turbulence. A structure emerges within the unstructured space plasma.
The results are published in The Astrophysical Journal Letters.
The team from the Institute of Theoretical Physics at the Technische Universität Braunschweig and the University of Tokyo, in collaboration with researchers from a total of 10 countries, has demonstrated a fundamentally new phenomenon.
Using high-precision magnetic field and particle data from NASA’s Parker Solar Probe mission, the team showed directly for the first time that the turbulent magnetic fields exhibit a clear reversal of the magnetic field rotation sense over a certain wavelength, and that the reversal grows and shifts toward longer wavelengths in the radial direction away from the sun. The reversal coincides with the transition from large-scale, fluid-like dynamics to small-scale, particle-like dynamics.
The discovery of a small-scale phenomenon has a big impact on science
On larger length scales, space plasma behaves like a fluid, and turbulence develops through excitation of vortices and electromagnetic waves. The fluctuations become random, that is, turbulent. However, the magnetic field rotation is not random. The fields preferentially rotate counterclockwise when viewed radially away from the sun.
The rotation, however, looks different on smaller length scales. The fields rotate clockwise when one looks at the turbulent plasma on smaller length scales. This scale coincides with the transition from flow-like behavior in the plasma to particle-like behavior.
“We see a clear structure in the spectrum, even though the turbulence represents unstructured motions,” says Dr. Masatomi Iizawa (TU Braunschweig), the first author of the article.
Dr. Yokoi (University of Tokyo) stresses the importance of this finding, “The results are of great significance for both plasma physics and astrophysics.”
A structure forms when the space plasma becomes turbulent, and the key insight lies in the transition from fluid dynamics to particle dynamics. Plasma turbulence plays an important role in astrophysics, such as in Earth’s magnetosphere, the solar wind, solar eruptions, interplanetary space and accretion disks.
Turbulence in space plasma can influence the shock waves and magnetic clouds in interplanetary space produced by solar eruptions and is an important factor in predicting geomagnetic storms.
Publication details
Masatomi Iizawa, et al. Nonlocal Evolution of Magnetic Helicity across the Magnetohydrodynamic–Kinetic Interface, The Astrophysical Journal Letters (2026). DOI: 10.3847/2041-8213/aea84b
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Structure in the unstructured: New phenomenon discovered in the solar wind (2026, October 13)
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