Convective dynamo action in a spherical shell: symmetries and modulation

We consider dynamo action driven by three-dimensional rotating anelastic convection in a spherical shell. Motivated by the behaviour of the solar dynamo, we examine the interaction of hydromagnetic modes with different symmetries and demonstrate how complicated interactions between convection, diffe...

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Bibliographic Details
Published inJournal of fluid mechanics Vol. 799; no. R6
Main Authors Raynaud, Raphaël, Tobias, Steven M.
Format Journal Article
LanguageEnglish
Published Cambridge, UK Cambridge University Press 25.07.2016
Cambridge University Press (CUP)
Subjects
Amplitude
Anelasticity
Astrophysics
Convection
Convection modes
Differential rotation
Fluid Dynamics
Fluid mechanics
Interactions
Isotopes
Magnetic field
Magnetic fields
Modulation
Parameters
Physics
Rapids
Rotation
Solar activity
Solar and Stellar Astrophysics
Solutions
Spherical shells
Sun
Sunspots
Switches
Symmetry
convection
MHD and electrohydrodynamics
Magnetohydrodynamics MHD
Stars magnetic fields
Dynamo action
Convection
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Summary:We consider dynamo action driven by three-dimensional rotating anelastic convection in a spherical shell. Motivated by the behaviour of the solar dynamo, we examine the interaction of hydromagnetic modes with different symmetries and demonstrate how complicated interactions between convection, differential rotation and magnetic fields may lead to modulation of the basic cycle. For some parameters, type 1 modulation occurs by the transfer of energy between modes of different symmetries with little change in the overall amplitude; for other parameters, the modulation is of type 2, where the amplitude is significantly affected (leading to grand minima in activity) without significant changes in symmetry. Most importantly, we identify the presence of ‘supermodulation’ in the solutions, where the activity switches chaotically between type 1 and type 2 modulation; this is believed to be an important process in solar activity.
ISSN:0022-1120
1469-7645
DOI:10.1017/jfm.2016.407