High Reynolds number magnetohydrodynamic turbulence using a Lagrangian model

• Autores: Pietarila Graham, J.; Mininni, Pablo Daniel; Pouquet, A.
• Año de publicación: 2011
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Subgrid Models; Conducting Flows; Regularized Equations; Turbulence
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

With the help of a model of magnetohydrodynamic (MHD) turbulence tested previously, we explore high Reynolds number regimes up to equivalent resolutions of 60003 grid points in the absence of forcing and with no imposed uniform magnetic field. For the given initial condition chosen here, with equal kinetic and magnetic energy, the flow ends up being dominated by the magnetic field, and the dynamics leads to an isotropic Iroshnikov-Kraichnan energy spectrum. However, the locally anisotropic magnetic field fluctuations perpendicular to the local mean field follow a Kolmogorov law. We find that the ratio of the eddy turnover time to the Alfvén time increases with wave number, contrary to the so-called critical balance hypothesis. Residual energy and helicity spectra are also considered; the role played by the conservation of magnetic helicity is studied, and scaling laws are found for the magnetic helicity and residual helicity spectra. We put these results in the context of the dynamics of a globally isotropic MHD flow that is locally anisotropic because of the influence of the strong large-scale magnetic field, leading to a partial equilibration between kinetic and magnetic modes for the energy and the helicity. © 2011 American Physical Society.
Fil: Pietarila Graham, J.. University Johns Hopkins; Estados Unidos
Fil: Mininni, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentina
Fil: Pouquet, A.. National Center for Atmospheric Research; Estados Unidos