PROPERTIES OF MAGNETIC HELICITY FLUX IN TURBULENT DYNAMOS

Autor:	Dmitry S. Shapovalov, Ethan T. Vishniac
Rok vydání:	2013
Předmět:	Physics Flux Astronomy and Astrophysics Mechanics Magnetohydrodynamic turbulence Helicity Magnetic flux Magnetic field Physics::Fluid Dynamics Classical mechanics Space and Planetary Science Magnetic helicity Magnetohydrodynamics Dynamo
Zdroj:	The Astrophysical Journal. 780:144
ISSN:	1538-4357 0004-637X
DOI:	10.1088/0004-637x/780/2/144
Popis:	We study the flux of small-scale magnetic helicity in simulations of driven statistically homogeneous magnetohydrodynamic turbulence in a periodic box with an imposed large-scale shear. The simulations show that in the regime of strong dynamo action the eddy-scale magnetic helicity flux has only two significant terms: advective motion driven by the large-scale velocity field and the Vishniac-Cho (VC) flux which moves helicity across the magnetic field lines. The contribution of all the other terms is negligible. The VC flux is highly correlated with the large-scale electromotive force and is responsible for large-scale dynamo action, while the advective term is not. The VC flux is driven by the anisotropy of the turbulence. We derive analytical expressions for it in terms of the small-scale velocity or magnetic field. These expressions are used to predict the existence and strength of dynamo action for different turbulent anisotropies and tested against the results of the simulations.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::41d26e566d1a9758e4f28b18551d2045 https://doi.org/10.1088/0004-637x/780/2/144 Zobrazit plný text záznamu