Towards a Unified Magnetohydrodynamic Theory Describing the Formation of Energy-Transport Barriers in Plasma Turbulence

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In this study we clarified that plasma rotation, helicity, cross helicity, and electric field are closely related to the magnetic-field generation and the suppression of turbulent transports in magnetohydrodynamic plasmas. The findings are summarized as follows :(1) It was shown that large-scale magnetic structures can be generated and sustained in turbulence by a combination of plasma-rotation and cross-helicity (velocity/magnetic-field correlation) effects. This is a manifestation of the turbulent dynamo and suppression of turbulent transport.A turbulence model that can describe the field-generation and turbulence-suppression was constructed.(2) The magnetohydrodynamic mechanism of electric-field transport suppression, with special reference to tokamak's reversed-shear confinement, was presented. The mechanism of plasmarotation generation due to the combination of electric-field-curvature and cross-helicity effects was also presented for the first time theoretically. The validity of the mechanisms was confirmed through a numerical simulation of a cylindrical plasma.(3) Generation and sustainment mechanisms or dynamos of global magnetic field in plasma turbulence were presented with special emphasis of the combination of the helicity (an index representing helcal properties of velocity and magnetic-field structures) and cross-helicity effects. These dynamos were applied to phenomena such as the geomagnetism, solar polarity reversal, and collimation of astrophysical jets, and shown to successfully describe characteristics of these phenomena.(4) Turbulence theories and modeling of fluids and plasmas were reviewed from the viewpoint of inhomogeneities of fields and plasma parameters. The similarity and dissimilarity between the theoretical methods analysing fluid and plasma turbulence were shown.