%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 α^{2}Ω 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 α^{2}-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