منابع مشابه
Astrophysical magnetic fields and nonlinear dynamo theory
The current understanding of astrophysical magnetic fields is reviewed with particular emphasis on nonlinear dynamo theory. Analytic and numerical results are discussed both for small scale dynamos, where helicity is unimportant, and for large scale dynamos, where kinetic helicity is crucial. Large scale dynamos produce small scale magnetic helicity as a waste product that quenches the large sc...
متن کاملThe Nonlinear Turbulent Dynamo
We simulate the evolution of an initially weak magnetic field in forced turbulence for a range of Prandtl numbers. The field grows exponentially with the Kulsrud-Anderson k 3/2 spectrum until the magnetic energy approaches the viscous-scale kinetic energy, where the magnetic forces then backreact on the velocity. Further growth proceeds more slowly until a saturated state is reached where the m...
متن کاملUniversal nonlinear small-scale dynamo.
We consider astrophysically relevant nonlinear MHD dynamo at large Reynolds numbers (Re). We argue that it is universal in a sense that magnetic energy grows at a rate which is a constant fraction C(E) of the total turbulent dissipation rate. On the basis of locality bounds we claim that this "efficiency of the small-scale dynamo", C(E), is a true constant for large Re and is determined only by...
متن کاملSolar Dynamo Theory
TheSun’smagnetic field is the engine and energy source driving all phenomena collectively defining solar activity, which in turn structures the whole heliosphere and significantly impacts Earth’s atmosphere down at least to the stratosphere. The solar magnetic field is believed to originate through the action of a hydromagnetic dynamo process operating in the Sun’s interior, where the strongly ...
متن کاملLagrangian Coherent Structures in a Nonlinear Dynamo
Turbulence and chaos play a fundamental role in stellar convective zones through the transport of particles, energy and momentum, and in fast dynamos, through the stretching, twisting and folding of magnetic flux tubes. A particularly revealing way to describe turbulent motions is through the analysis of Lagrangian coherent structures (LCS), which are material lines or surfaces that act as tran...
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ژورنال
عنوان ژورنال: The Astrophysical Journal
سال: 1999
ISSN: 0004-637X,1538-4357
DOI: 10.1086/306877