Mean-field and direct numerical simulations of magnetic flux concentrations from vertical field

AbstractWe summarise recent results form direct numerical simulations of both non-rotating helically forced and rotating convection driven MHD equations in spherical wedge-shape domains. In the former, using perfect-conductor boundary conditions along the latitudinal boundaries we observe oscillations, polarity reversals and equatorward migration of the large-scale magnetic fields. In the latter we obtain angular velocity with cylindrical contours and large-scale magnetic field which shows oscillations, polarity reversals but poleward migration. The occurrence of these behviours in direct numerical simulations is clearly of interest. However the present models as they stand are not directly applicable to the solar dynamo problem. Nevertheless, they provide general insights into the operation of turbulent dynamos.

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MEAN-FIELD MODELING OF AN α 2 DYNAMO COUPLED WITH DIRECT NUMERICAL SIMULATIONS OF RIGIDLY ROTATING CONVECTION

The Astrophysical Journal ◽

10.1088/2041-8205/794/1/l6 ◽

2014 ◽

Vol 794 (1) ◽

pp. L6 ◽

Cited By ~ 11

Author(s):

Youhei Masada ◽

Takayoshi Sano

Keyword(s):

Numerical Simulations ◽

Mean Field ◽

Direct Numerical Simulations ◽

Rotating Convection ◽

Field Modeling

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The Solar Dynamo: Old, Recent, and New Problems

Symposium - International Astronomical Union ◽

10.1017/s0074180900218949 ◽

2001 ◽

Vol 203 ◽

pp. 144-151

Author(s):

A. Brandenburg

Keyword(s):

Numerical Simulations ◽

Mean Field ◽

Direct Numerical Simulations ◽

Solar Dynamo ◽

Magnetic Helicity ◽

Current Status ◽

Dynamo Theory ◽

Inverse Cascade ◽

Mean Field Dynamo ◽

Stellar Dynamo

A number of problems of solar and stellar dynamo theory are briefly reviewed and the current status of possible solutions is discussed. Results of direct numerical simulations are described in view of mean-field dynamo theory and the relation between the α-effect and the inverse cascade of magnetic helicity is highlighted. The possibility of ‘catastrophic’ quenching of the α-effect is explained in terms of the constraint placed by the conservation of magnetic helicity.

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Global dynamo models from direct numerical simulations and their mean-field counterparts

Astronomy and Astrophysics ◽

10.1051/0004-6361/201116642 ◽

2011 ◽

Vol 533 ◽

pp. A108 ◽

Cited By ~ 12

Author(s):

M. Schrinner

Keyword(s):

Numerical Simulations ◽

Mean Field ◽

Direct Numerical Simulations

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Magnetic helicity fluxes and their effect on stellar dynamos

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312004620 ◽

2011 ◽

Vol 7 (S286) ◽

pp. 49-53

Author(s):

Simon Candelaresi ◽

Axel Brandenburg

Keyword(s):

Numerical Simulations ◽

Mean Field ◽

Reynolds Numbers ◽

Direct Numerical Simulations ◽

Critical Values ◽

Magnetic Helicity ◽

Dynamic Quenching ◽

Dynamo Action ◽

One Dimensional ◽

Field Formalism

AbstractMagnetic helicity fluxes in turbulently driven α2 dynamos are studied to demonstrate their ability to alleviate catastrophic quenching. A one-dimensional mean-field formalism is used to achieve magnetic Reynolds numbers of the order of 105. We study both diffusive magnetic helicity fluxes through the mid-plane as well as those resulting from the recently proposed alternate dynamic quenching formalism. By adding shear we make a parameter scan for the critical values of the shear and forcing parameters for which dynamo action occurs. For this αΩ dynamo we find that the preferred mode is antisymmetric about the mid-plane. This is also verified in 3-D direct numerical simulations.

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