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arXiv · 0705.2308

Evolution of Magnetic Fields in Freely Decaying Magnetohydrodynamic Turbulence

Leonardo Campanelli
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Abstract

We study the evolution of magnetic fields in freely decaying magnetohydrodynamic turbulence. By quasi-linearizing the Navier-Stokes equation, we solve analytically the induction equation in quasi-normal approximation. We find that, if the magnetic field is not helical, the magnetic energy and correlation length evolve in time respectively as E_B \propto t^{-2(1+p)/(3+p)} and ξ_B \propto t^{2/(3+p)}, where p is the index of initial power-law spectrum. In the helical case, the magnetic helicity is an almost conserved quantity and forces the magnetic energy and correlation length to scale as E_B \propto (log t)^{1/3} t^{-2/3} and ξ_B \propto (log t)^{-1/3} t^{2/3}.

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Leonardo Campanelli. 2007-05-16. Evolution of Magnetic Fields in Freely Decaying Magnetohydrodynamic Turbulence. https://doi.org/10.1103/physrevlett.98.251302

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