منابع مشابه
Magnetic Helicity and Energy Spectra of a Solar Active Region
We compute magnetic helicity and energy spectra of the solar active region NOAA 11158 during 11–15 February 2011 at 20 southern heliographic latitude using observational photospheric vector magnetograms. We adopt the isotropic representation of the Fourier-transformed two-point correlation tensor of the magnetic field. The sign of magnetic helicity turns out to be predominantly positive at all ...
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Magnetic field amplification in astrophysics ultimately requires an understanding of magnetohydrodynamic turbulence. Kinetic helicity has long been known to be important for large scale field growth in forced MHD turbulence, and has been recently demonstrated numerically to be asymptotically consistent with slow mean field dynamo action in a periodic box. Here we show numerically that the magne...
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We consider the NS-alpha and the family of high accuracy, NS-alpha-deconvolution models of turbulence on Ω = [0, LΩ] 3 subject to periodic boundary conditions. For body force driven turbulence, we prove directly from the model equations of motion the following bounds on the time averaged modified energy dissipation rate, 〈εα,N(wα,N)〉, and unmodified helicity dissipation rate, 〈γ(wα,N)〉, for the...
متن کاملMagnetohydrodynamic dissipation range spectra for isotropic viscosity and resistivity
Dissipation range spectra for incompressible magnetohydrodynamic turbulence are derived for isotropic viscosity and resistivity . The spectra are obtained from heuristic closures of spectral transfer correlations for cases with Pm= / 1, where Pm is the magnetic Prandtl number. Familiar inertial range power laws are modified by exponential factors that dominate spectral falloff in the dissipatio...
متن کاملLinks between dissipation, intermittency, and helicity in the GOY model revisited
High resolution simulations within the GOY shell model are used to study various scaling relations for turbulence. A power-law relation between the second-order intermittency correction and the crossover from the inertial to the dissipation range is confirmed. Evidence is found for the intermediate viscous dissipation range proposed by Frisch and Vergassola. It is emphasized that insufficient d...
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ژورنال
عنوان ژورنال: Physics Letters A
سال: 2008
ISSN: 0375-9601
DOI: 10.1016/j.physleta.2008.06.079