IFIBA   22255
INSTITUTO DE FISICA DE BUENOS AIRES
Unidad Ejecutora - UE
artículos
Título:
High Reynolds number magnetohydrodynamic turbulence using a Lagrangian model
Autor/es:
J. PIETARILA GRAHAM; P.D. MININNI; A. POUQUET
Revista:
PHYSICAL REVIEW E
Editorial:
AMER PHYSICAL SOC
Referencias:
Año: 2011 vol. 84 p. 163141 - 163149
ISSN:
1539-3755
Resumen:
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.