Turbulent transport of magnetic fields. V. Distribution of magnetic energy in a simple α2-dynamo
作者:
J.H. G. M. Van Geffen,
P. Hoyng,
期刊:
Geophysical & Astrophysical Fluid Dynamics
(Taylor Available online 1990)
卷期:
Volume 53,
issue 1-2
页码: 109-123
ISSN:0309-1929
年代: 1990
DOI:10.1080/03091929008208924
出版商: Taylor & Francis Group
关键词: Alpha2-dynamos;dynamo processes;helicity;mean-field MHD;turbulence;vorticity;stochastic processes
数据来源: Taylor
摘要:
The stationary solution depends on two coefficients describing the turbulent state: the diffusion coefficient β≈⟨u2⟩τc/3 and the vorticity coefficient γ ≈ ⟨|▿×u|2⟩τc/3 whereu(r,t) is the turbulent velocity andcits correlation time. But the solution is independent of the dynamo coefficient α≈−⟨u·▿×u⟩τc/3 although α does occur in the equation forTij. This result confirms earlier conclusions that helicity is not required for magnetic field generation. In the stationary state, magnetic energy is generated by the vorticity and transported to the boundary, where it escapes at the same rate. The solution presented contains one free parameter that is connected with the distribution ofBover spatial scales at the boundary, about whichTijgives no information. We regard this investigation as a first step towards the analysis of more complicated, solar-type dynamos.
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