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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 606391.0, MPI für Astronomie / Publikationen_mpia
Oscillatory dynamos and their induction mechanisms
Authors:Schrinner, M.; Petitdemange, L.; Dormy, E.
Date of Publication (YYYY-MM-DD):2011
Journal Abbrev.:Astronomy and Astrophysics
Start Page:140
Audience:Not Specified
Abstract / Description:Context. Large-scale magnetic fields resulting from hydromagnetic dynamo action may differ substantially in their time dependence. Cyclic field variations, characteristic for the solar magnetic field, are often explained by an important Ω-effect, i.e., by the stretching of field lines because of strong differential rotation. <BR /> Aims: The dynamo mechanism of a convective, oscillatory dynamo model is investigated. <BR /> Methods: We solve the MHD-equations for a conducting Boussinesq fluid in a rotating spherical shell. We computed the dynamo coefficients for the resulting oscillatory model with the help of the so-called test-field method. Subsequently, these coefficients were used in a mean-field calculation to explore the underlying dynamo mechanism. <BR /> Results: The oscillatory dynamo model we consider is an α2Ω one. Although the fairly strong differential rotation of this model influences the magnetic field, the Ω-effect alone is not responsible for its cyclic time variation. If the Ω-effect is suppressed, the resulting α2-dynamo remains oscillatory. Surprisingly, the corresponding αΩ-dynamo leads to a non-oscillatory magnetic field. <BR /> Conclusions: The assumption of an αΩ-mechanism does not explain the occurrence of magnetic cycles satisfactorily.
Free Keywords:dynamo; magnetohydrodynamics (MHD); magnetic fields; Sun: dynamo
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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