Speaker
Description
Magnetic clouds are multi-scale structures: coronal flux ropes evolve to become as wide as 0.2 AU near the Earth; their magnetic fields vary on scales smaller than their average size, and present turbulent fluctuations. We perform high resolution 2.5D MHD simulations to study a magnetic flux rope cross section in the expanding solar wind together with turbulence: we investigate how turbulence and expansion impact the magnetic cloud coherence, using virtual spacecraft. The flux rope cross section expands at large scales due to the solar wind flow and to internal magnetic forces, whereas turbulence distorts, deflects, and reshapes the plasma at intermediate and small scales. We find that magnetic cloud coherence is dominated by expansion and internal magnetic forces: clear and stable signatures are present inside the flux rope core; turbulence becomes effective when magnetic tension is weak, and mixed signatures appear at the flux rope edges. Fast expansion implies a more elongated cross section: magnetic cloud signatures encountered across a wider angle. Strong turbulence can produce a more asymmetric and distorted cross section: different plasma profiles appear at different angles. Mixed signatures at the edges depend mainly on how well magnetic tension bounds the flux rope field, and they disappear for narrow flux ropes. Implication of such study of the forthcoming HENON mission will be discussed.
