Magnetoconvection and dynamo coefficients III: alpha-effect and magnetic pumping in the rapid rotation regime

Abstract

Aims. The alpha- and gamma-effects, which are responsible for the generation and turbulent pumping of large scale magnetic fields, respectively, due to passive advection by convection are determined in the rapid rotation regime corresponding to the deep layers of the solar convection zone. Methods. A 3D rectangular local model is used for solving the full set of MHD equations in order to compute the electromotive force (emf), E = <u x b>, generated by the interaction of imposed weak gradient-free magnetic fields and turbulent convection with varying rotational influence and latitude. By expanding the emf in terms of the mean magnetic field, E_i = a_ij <B_j>, all nine components of a_ij are computed. The diagonal elements of a_ij describe the alpha-effect, whereas the off-diagonals represent magnetic pumping. The latter is essentially the advection of magnetic fields by means other than the underlying large-scale velocity field. Comparisons are made to analytical expressions of the coefficients derived under the first-order smoothing approximation (FOSA). Results. In the rapid rotation regime the latitudinal dependence of the alpha-components responsible for the generation of the azimuthal and radial fields does not exhibit a peak at the poles, as is the case for slow rotation, but at a latitude of about 30 degrees. The magnetic pumping is predominantly radially down- and latitudinally equatorward as in earlier studies. The numerical results compare surprisingly well with analytical expressions derived under first-order smoothing, although the present calculations are expected to lie near the limits of the validity range of FOSA.

14 pages, 12 figures, accepted for publication in Astronomy & Astrophysics

References in corpus (10)

• Magnetic Helicity Conservation and Astrophysical Dynamos
• Solar differential rotation and meridional flow: The role of a subadiabatic tachocline for the Taylor-Proudman balance
• Magnetoconvection and dynamo coefficients: II. Field-direction dependent pumping of magnetic field
• Non-Fickian diffusion and tau approximation from numerical turbulence
• Minimal tau approximation and simulations of the alpha effect
• Magnetoconvection and dynamo coefficients: Dependence of the alpha-effect on rotation and magnetic field
• Local models of stellar convection: Reynolds stresses and turbulent heat transport
• Catastrophic alpha quenching alleviated by helicity flux and shear
• A 3D MHD model of astrophysical flows: algorithms, tests and parallelisation
• Local models of stellar convection III: The Strouhal number

Cited by in corpus (37)

• Effects of enhanced stratification on equatorward dynamo wave propagation
• Large-scale dynamos in turbulent convection with shear
• Grand Minima and Equatorward Propagation in a Cycling Stellar Convective Dynamo
• Is a deep one-cell meridional circulation essential for the flux transport Solar Dynamo?
• A Solar Dynamo Model Driven by Mean-Field Alpha and Babcock-Leighton Sources: Fluctuations, Grand-Minima-Maxima and Hemispheric Asymmetry in Sunspot Cycles
• Alpha effect and turbulent diffusion from convection
• Turbulent magnetic pumping in a Babcock-Leighton solar dynamo model
• Convective dynamos in spherical wedge geometry
• Turbulent Pumping of Magnetic Flux Reduces Solar Cycle Memory and thus Impacts Predictability of the Sun's Activity
• Large-scale dynamos in rigidly rotating turbulent convection
• Turbulent transport coefficients in spherical wedge dynamo simulations of solar-like stars
• Alpha effect and diffusivity in helical turbulence with shear
• Combined magnetic and gravity measurements probe the deep zonal flows of the gas giants
• A new dynamo pattern revealed by the tilt angle of bipolar sunspot groups
• Mean field models of flux transport dynamo and meridional circulation in the Sun and stars
• Recovery from Maunder-like Grand Minima in a Babcock--Leighton Solar Dynamo Model
• The alpha effect with imposed and dynamo-generated magnetic fields
• The alpha effect in rotating convection with sinusoidal shear
• Pumping velocity in homogeneous helical turbulence with shear
• Effects of a subadiabatic layer on convection and dynamos in spherical wedge simulations
• Turbulent processes and mean-field dynamo
• Physical Origin of Differences among various Measures of Solar Meridional Circulation
• Effects of turbulent pumping on stellar activity cycles
• Exploring cycle period and parity of stellar magnetic activity with dynamo modeling
• Mean-Field Modeling of ${\alpha }^2$-Dynamo Coupled with Direct Numerical Simulations of Rigidly Rotating Convection
• Does the mean-field alpha effect have any impact on the memory of the solar cycle?
• Diamagnetic pumping near the base of a stellar convection zone
• Is hemispheric asymmetry in the sunspot cycle solely governed by polar flux imbalance in the previous cycle?
• Robustness of oscillatory ${\alpha }^2$ dynamos in spherical wedges
• Nonkinematic solar dynamo models with double-cell meridional circulation
• Diamagnetic pumping in a rotating convection zone
• On global solar dynamo simulations
• An advective solar-type dynamo without the alpha effect
• Constraining Jupiter's internal flows using Juno magnetic and gravity measurements
• A Potential New Mechanism for the Butterfly Diagram of the Solar Cycle: Latitude-dependent Radial Flux Transport
• Helicity-vorticity turbulent pumping of magnetic fields in solar convection zone
• Effect of Nonlinear Surface Inflows into Activity Belts on Solar Cycle Modulation