Parker finds opposite magnetic twists at different solar-wind scales
Parker Solar Probe measurements reveal an organized pattern inside turbulent solar wind: larger magnetic structures favor one twisting direction, smaller ones the other. A peer-reviewed study links the change to the boundary between fluid-like and particle behavior. The observations constrain turbulence models, while leaving the mechanism and its consistency across other periods unresolved.
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Magnetic direction changes with scale
Inside the Sun’s outward flow of charged particles, magnetic structures do not all twist the same way. An international team identified a reversal between larger and smaller scales in measurements from Parker Solar Probe. The finding, published in The Astrophysical Journal Letters, puts an organized feature inside an otherwise turbulent plasma. Large structures favored left-handed rotation when viewed relative to the direction away from the Sun; smaller ones favored right-handed rotation. The change appeared near the boundary where a fluid description gives way to the behavior of individual charged particles.[1], [2]
The pattern shifts farther from the Sun
The analysis used observations from autumn 2021. Between approximately 15 and 60 million kilometres from the Sun, the characteristic pattern shifted from higher to lower frequencies. If solar-wind flow carries these structures past the spacecraft, that shift corresponds to larger spatial structures. The researchers interpret it as evidence consistent with magnetic structure transferring from smaller scales to larger ones. The calculated shift was larger than that expected from simple expansion alone. Beyond roughly 75 million kilometres, the two-direction pattern became less distinct.[1]
The mechanism remains unresolved
These are comparisons of observations at different distances, rather than a record of one plasma parcel’s complete journey. Some intervals lacked direct flow-speed measurements, so the analysis used an average. Several waves and plasma instabilities could contribute to the pattern, and their relative roles remain unresolved. A limited observation period also leaves its consistency across other solar-wind conditions open. The result provides a constraint for turbulence models; improved solar-storm forecasts have not yet been demonstrated.[1]
