Kinematic-Dynamo Theory. II. Dynamo Action in Infinite Media with Isotropic Turbulence

1971 ◽  
Vol 166 ◽  
pp. 639 ◽  
Author(s):  
I. Lerche
Keyword(s):  
Isotropic Turbulence ◽  
Dynamo Theory ◽  
Dynamo Action ◽  
Kinematic Dynamo ◽  
Infinite Media

Turbulent dynamo action at low magnetic Reynolds number

1970 ◽  
Vol 41 (2) ◽  
pp. 435-452 ◽  
Author(s):  
H. K. Moffatt
Keyword(s):  
Magnetic Field ◽  
Reynolds Number ◽  
Large Scale ◽  
Isotropic Turbulence ◽  
Magnetic Energy ◽  
Magnetic Reynolds Number ◽  
Dynamo Action ◽  
Ohmic Dissipation ◽  
Magnetic Energy Density ◽  
Magnetic Diffusivity

The effect of turbulence on a magnetic field whose length-scale L is initially large compared with the scale l of the turbulence is considered. There are no external sources for the field, and in the absence of turbulence it decays by ohmic dissipation. It is assumed that the magnetic Reynolds number Rm = u0l/λ (where u0 is the root-mean-square velocity and λ the magnetic diffusivity) is small. It is shown that to lowest order in the small quantities l/L and Rm, isotropic turbulence has no effect on the large-scale field; but that turbulence that lacks reflexional symmetry is capable of amplifying Fourier components of the field on length scales of order Rm−2l and greater. In the case of turbulence whose statistical properties are invariant under rotation of the axes of reference, but not under reflexions in a point, it is shown that the magnetic energy density of a magnetic field which is initially a homogeneous random function of position with a particularly simple spectrum ultimately increases as t−½exp (α2t/2λ3) where α(= O(u02l)) is a certain linear functional of the spectrum tensor of the turbulence. An analogous result is obtained for an initially localized field.

scholarly journals Numerical simulations of kinematic dynamo action

2002 ◽  
Vol 397 (2) ◽  
pp. 393-399 ◽  
Author(s):  
V. Archontis ◽  
S. B. F. Dorch ◽  
Å. Nordlund
Keyword(s):  
Numerical Simulations ◽  
Dynamo Action ◽  
Kinematic Dynamo

scholarly journals Competing kinematic dynamo mechanisms in rotating convection with shear

2010 ◽  
Vol 6 (S271) ◽  
pp. 239-246 ◽  
Author(s):  
Michael R. E. Proctor ◽  
David W. Hughes
Keyword(s):  
Growth Rates ◽  
Convective Flow ◽  
Flow Fields ◽  
Velocity Shear ◽  
Dynamo Action ◽  
Preliminary Results ◽  
Rotating Convection ◽  
Kinematic Dynamo

AbstractFollowing earlier work by Hughes & Proctor (2009) on the role of velocity shear in convectively driven dynamos, we present preliminary results on the nature of dynamo action due to modified flows derived by filtration from the full convective flow. The results suggest that filtering the flow fields has surprisingly little effect on the dynamo growth rates.

scholarly journals Onward from solar convection to dynamos in cores of massive stars

2010 ◽  
Vol 6 (S271) ◽  
pp. 347-352
Author(s):  
Juri Toomre
Keyword(s):  
Convection Zone ◽  
Massive Stars ◽  
Dynamo Theory ◽  
Dynamo Action ◽  
Surface Shear ◽  
Near Surface ◽  
Solar Convection ◽  
Core Convection ◽  
Central Regions ◽  
Ultimate Fate

AbstractWe reflect upon a few of the research challenges in stellar convection and dynamo theory that are likely to be addressed in the next five or so years. These deal firstly with the Sun and continuing study of the two boundary layers at the top and bottom of its convection zone, namely the tachocline and the near-surface shear layer, both of which are likely to have significant roles in how the solar dynamo may be operating. Another direction concerns studying core convection and dynamo action within the central regions of more massive A, B and O-type stars, for the magnetism may have a key role in controlling the winds from these stars, thus influencing their ultimate fate. Such studies of the interior dynamics of massive stars are becoming tractable with recent advances in codes and supercomputers, and should also be pursued with some vigor.

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