AU research reveals presence of helicity barrier the the near-Sun solar wind
New research utilising data from NASA’s Parker Solar Probe has provided the first direct evidence of a phenomenon known as the “helicity barrier” in the solar wind. This discovery, published in Physical Review X by Queen Mary University of London researchers, offers a significant step towards understanding two long-standing mysteries: how the Sun’s atmosphere is heated to millions of degrees and how the supersonic solar wind is generated.
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The solar atmosphere, or corona, is far hotter than the Sun's surface, a paradox that has puzzled scientists for decades. Furthermore, the constant outflow of plasma and magnetic fields from the Sun, known as the solar wind, is accelerated to incredible speeds. Turbulent dissipation – the process by which mechanical energy is converted into heat – is believed to play a crucial role in both these phenomena. However, in the near-Sun environment, where plasma is largely collisionless, the exact mechanisms of this dissipation have remained elusive.
This new study, led by AU PhD student Jack McIntyre and his supervisor Dr Christopher Chen, leverages data from NASA's Parker Solar Probe, which has become the closest spacecraft to the Sun, flying directly through the solar atmosphere. This unprecedented proximity allowed researchers to directly explore this extreme environment for the first time, providing critical data to unravel these mysteries. The paper presents compelling evidence that the "helicity barrier" is active and profoundly alters the nature of turbulent dissipation. This effect, previously theorised, creates a barrier to the turbulent cascade of energy at small scales, fundamentally changing how fluctuations dissipate and thus how the plasma is heated.