Astronomy and Astrophysics – Astrophysics
Scientific paper
2008-07-07
Astronomische Nachrichten 329, No. 7, 737 - 749 (2008)
Astronomy and Astrophysics
Astrophysics
13 pages, 10 figures, version published in Astronomische Nachrichten
Scientific paper
10.1002/asna.200811018
Numerical simulations of forced turbulence in elongated shearing boxes are carried out to demonstrate that a nonhelical turbulence in conjunction with a linear shear can give rise to a mean-field dynamo. Exponential growth of magnetic field at scales larger than the outer (forcing) scale of the turbulence is found. Over a range of values of the shearing rate S spanning approximately two orders of magnitude, the growth rate of the magnetic field is proportional to the imposed shear, gamma ~ S, while the characteristic spatial scale of the field is l_b ~ S^(-1/2). The effect is quite general: earlier results for the nonrotating case by Yousef et al. 2008 (PRL 100, 184501) are extended to shearing boxes with Keplerian rotation; it is also shown that the shear dynamo mechanism operates both below and above the threshold for the fluctuation dynamo. The apparently generic nature of the shear dynamo effect makes it an attractive object of study for the purpose of understanding the generation of magnetic fields in astrophysical systems.
Cowley Steve C.
Heinemann Tobias
Kleeorin Nathan
McWilliams James C.
Rincon Felipe
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