%0 Journal Article %T Oscillatory dynamos and their induction mechanisms %+ Institut de Physique du Globe de Paris (IPGP) %A Schrinner, M. %A Petitdemange, L. %A Dormy, E. %< avec comité de lecture %@ 0004-6361 %J Astronomy and Astrophysics - A&A %I EDP Sciences %V 530 %8 2011 %D 2011 %Z 1101.1837 %Z 2011A&A...530A.140S %R 10.1051/0004-6361/201016372 %K dynamo %K magnetohydrodynamics (MHD) %K magnetic fields %K Sun: dynamo %K Astrophysics - Solar and Stellar Astrophysics %Z Sciences of the Universe [physics] %Z Sciences of the Universe [physics]/Astrophysics [astro-ph]Journal articles %X 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.
Aims: The dynamo mechanism of a convective, oscillatory dynamo model is investigated.
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.
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.
Conclusions: The assumption of an αΩ-mechanism does not explain the occurrence of magnetic cycles satisfactorily. %G English %2 https://insu.hal.science/insu-03606479/document %2 https://insu.hal.science/insu-03606479/file/aa16372-10.pdf %L insu-03606479 %U https://insu.hal.science/insu-03606479 %~ INSU %~ UNIV-PARIS7 %~ AFRIQ %~ CNRS %~ IPGP %~ SORBONNE-UNIVERSITE %~ UNIV-PARIS %~ SU-TI %~ ALLIANCE-SU