insu-03606479
https://insu.hal.science/insu-03606479
https://insu.hal.science/insu-03606479/document
https://insu.hal.science/insu-03606479/file/aa16372-10.pdf
arxiv:1101.1837
doi:10.1051/0004-6361/201016372
[INSU] INSU - Institut National des Sciences de l'Univers
[UNIV-PARIS7] Université Denis Diderot - Paris VII
[AFRIQ] HAL-Francophonie, Afrique et océan indien
[CNRS] CNRS - Centre national de la recherche scientifique
[IPGP] Institut de Physique du Globe de Paris
[SORBONNE-UNIVERSITE] Sorbonne Université
[UNIV-PARIS] Université Paris Cité
[SU-TI] Sorbonne Université - Texte Intégral
[ALLIANCE-SU] Alliance Sorbonne Université
Oscillatory dynamos and their induction mechanisms
Schrinner, M.
Petitdemange, L.
Dormy, E.
[SDU] Sciences of the Universe [physics]
[SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph]
ART
dynamo
magnetohydrodynamics (MHD)
magnetic fields
Sun: dynamo
Astrophysics - Solar and Stellar Astrophysics
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 α<SUP>2</SUP>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<SUP>2</SUP>-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.
2011
2022-03-12
en
Astronomy and Astrophysics - A&A
EDP Sciences