Solar-wind magnetic fields preferentially rotate one way at large scales and the other at small ones

On larger scales the plasma behaves like a fluid, and its fluctuations become random. The magnetic-field rotation is the exception: it is not random ^[8]. "We see a clear structure in the spectrum, even though the turbulence represents unstructured motions," said Masatomi Iizawa of TU Braunschweig, the paper's first author ^[10].

The result comes from spacecraft measurements, so it has no control arm of the kind a lab experiment would ^[3]. Its main protection against being an artefact of data handling is where it falls: at the transition between fluid-like and particle-like dynamics, a boundary with its own physics ^[5].

Space plasma is collisionless, meaning it is so dilute that its particles do not collide with each other ^[7]. According to the phys.org summary, how fluctuation energy is distributed in that kind of turbulence is still an open question ^[9].

The phys.org summary does not report the reversal's wavelength, its amplitude, how many Parker Solar Probe intervals went into it, or over what range of distances from the sun. The claim to be first is the team's own ^[1].

The space-weather link is broad. Turbulence can influence the shock waves and magnetic clouds that solar eruptions send into interplanetary space, and it is an important factor in predicting geomagnetic storms ^[12]. We'd expect the first use of the reversal to be in turbulence theory and simulation, where it gives models a feature to match. A forecasting benefit would need its own demonstration.

"The results are of great significance for both plasma physics and astrophysics," said Yokoi of the University of Tokyo ^[11].