On effects of surface bipolar magnetic regions on the convection zone dynamo

Abstract

We investigate the effect of the surface bipolar magnetic regions (BMR) on the large-scale dynamo distributed in the bulk of the convection zone. The study employs the nonlinear 3D mean-field dynamo model. We model the emergence of the BMR on the surface through the nonaxisymmetric magnetic buoyancy effect, which acts on the large-scale toroidal magnetic field in the upper half of the convection zone. The nonaxisymmetric magnetic field which results from this mechanism is shallow. On the surface, the effect of the BMR on the magnetic field generation is dominant. {However, because of the shallow BMR distribution, its effect on the global dynamo is less compared to the convective zone dynamo.} We find that the mean-field $\alpha$ effect, which acts on the nonaxisymmetric magnetic field of the BMRs, provides the greater contribution to the dynamo process than the BMR's tilt does. Even so, the fluctuations of the BMR's tilt lead to the parity braking in the global dynamo. At the surface the nonaxisymmetric magnetic field, which are generated because of the BMR's activity, shows a tendency for the bihelical spectrum with the positive sign for the low $\ell$ modes during the maximum of the magnetic activity cycle.

arXiv comment14 pages, 12 figures, accepted in MNRAS

References in corpus (52)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Efficient Spherical Harmonic Transforms aimed at pseudo-spectral numerical simulations
• The Sun's Global Photospheric and Coronal Magnetic Fields: Observations and Models
• Exploring the Physical Basis of Solar Cycle Predictions: Flux Transport Dynamics and Persistence of Memory in Advection versus Diffusion Dominated Solar Convection Zones
• Bipolar Magnetic Regions on the Sun: Global Analysis of the SOHO/MDI Data Set
• Doubly Helical Coronal Ejections from Dynamos and their Role in Sustaining the Solar Cycle
• On the Formation of Active Regions
• A Solar Dynamo Model Driven by Mean-Field Alpha and Babcock-Leighton Sources: Fluctuations, Grand-Minima-Maxima and Hemispheric Asymmetry in Sunspot Cycles
• Solar magnetic fields as revealed by Stokes polarimetry
• Magnetic Helicity Tensor for an Anisotropic Turbulence
• Advances in mean-field dynamo theory and applications to astrophysical turbulence
• New dynamo pattern revealed by solar helical magnetic fields
• Evolution of coexisting long and short period stellar activity cycles
• A 3D Babcock-Leighton Solar Dynamo Model
• Equatorial magnetic helicity flux in simulations with different gauges
• The Solar-Stellar Connection
• Oscillatory dynamos and their induction mechanisms
• The subsurface-shear shaped solar $\alpha \Omega$ dynamo
• Catastrophic quenching in alpha-Omega dynamos revisited
• The mean electro-motive force, current- and cross-helicity under the influence of rotation, magnetic field and shear
• The Sun's Preferred Longitudes and the Coupling of Magnetic Dynamo Modes
• Magnetic Flux Transport and the Long-Term Evolution of Solar Active Regions
• A new dynamo pattern revealed by the tilt angle of bipolar sunspot groups
• Global dynamo models from direct numerical simulations and their mean-field counterparts
• The Origin of Parity Changes in the Solar Cycle
• Self-assembly of shallow magnetic spots through strongly stratified turbulence
• Signatures of Solar Cycle 25 in Subsurface Zonal Flows
• On the Origin of Solar Torsional Oscillations and Extended Solar Cycle
• Two-scale analysis of solar magnetic helicity
• Influence of random fluctuations in the Lambda-effect on meridional flow and differential rotation
• An update of Leighton's solar dynamo model
• A 3D kinematic Babcock Leighton solar dynamo model sustained by dynamic magnetic buoyancy and flux transport processes
• The magnetic field vector of the Sun-as-a-star. II. Evolution of the large-scale vector field through activity cycle 24
• Nonlinear regimes in mean-field full-sphere dynamo
• Evolution of Magnetic Helicity in Solar Cycle 24
• Helicity conservation in nonlinear mean-field solar dynamo
• Torsional Oscillations in Dynamo Models with Fluctuations and Potential for Helioseismic Predictions of the Solar Cycles
• The mean tilt of sunspot bipolar regions: theory, simulations and comparison with observations
• Evolution of Subsurface Zonal and Meridional Flows in Solar Cycle 24 from Helioseismological Data
• Measuring stellar magnetic helicity density
• Solar dynamo cycle variations with a rotational period
• Stellar dynamo models with prominent surface toroidal fields
• Nonkinematic solar dynamo models with double-cell meridional circulation
• Structure and evolution of the photospheric magnetic field in 2010 - 2017: comparison of SOLIS/VSM vector field and $B_{LOS}$ potential field
• A global two-scale helicity proxy from $\pi$-ambiguous solar magnetic fields
• The Minimal Helicity of Solar Coronal Magnetic Fields
• The origin and effect of hemispheric helicity imbalance in solar dynamo
• A new look at sunspot formation using theory and observations
• The magnetic helicity density patterns from non-axisymmetric solar dynamo

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