Turbulence in the solar wind has long been treated as the archetype of disorder: a churning plasma in which magnetic fields tangle without pattern. An international team including researchers at the University of Tokyo has now shown otherwise. Using high-precision magnetic field and particle measurements from NASA's Parker Solar Probe, the group reports the first direct demonstration of a reversal in the sense of magnetic field rotation within space turbulence, a structure hiding inside the apparently unstructured.
The analysis shows that on larger scales the fields preferentially rotate anticlockwise when viewed radially away from the Sun, while on smaller scales they rotate clockwise. The reversal grows and shifts towards longer wavelengths with increasing distance from the Sun, and it coincides with the transition from large-scale, fluid-like behaviour to small-scale dynamics governed by individual particles, a boundary of deep interest to plasma physicists.
The study, led by the Technische Universitaet Braunschweig with the University of Tokyo and colleagues at Tohoku, Kyushu and Osaka universities, drew on researchers from ten countries and appears in The Astrophysical Journal Letters. Because plasma turbulence shapes the Earth's magnetosphere, solar eruptions and accretion discs around black holes, the finding bears directly on efforts to predict geomagnetic storms that threaten satellites and power grids.