Lorentz force mediation of turbulent dynamo transitions
arXiv:2501.02306 · doi:10.1093/mnras/staf1081
Abstract
We investigate how the strength of the Lorentz force alters stellar convection zone dynamics in a suite of buoyancy-dominated, three-dimensional, spherical shell convective dynamo models. This is done by varying only the magnetic Prandtl number, , the non-dimensional form of the fluid's electrical conductivity . Because the strength of the dynamo magnetic field and the Lorentz force scale with , it is found that the fluid motions, the pattern of convective heat transfer, and the mode of dynamo generation all differ across the range investigated here. For example, we show that strong magnetohydrodynamic effects cause a fundamental change in the surface zonal flows: differential rotation switches from solar-like (prograde equatorial zonal flow) for larger electrical conductivities to an anti-solar differential rotation (retrograde equatorial zonal flow) at lower electrical conductivities. This study shows that the value of the bulk electrical conductivity is important not only for sustaining dynamo action, but can also drive first-order changes in the characteristics of the magnetic, velocity, and temperature fields. It is also associated with the relative strength of the Lorentz force in the system as measured by the local magnetic Rossby number, , which we show is crucial in setting the characteristics of the large-scale convection regime that generates those dynamo fields.
References in corpus (54)
- Turbulent geodynamo simulations: a leap towards Earth's core
- Efficient Spherical Harmonic Transforms aimed at pseudo-spectral numerical simulations
- From solar-like to anti-solar differential rotation in cool stars
- Approaching the Asymptotic Regime of Rapidly Rotating Convection: Boundary Layers vs Interior Dynamics
- Numerical study of dynamo action at low magnetic Prandtl numbers
- Effects of compressibility on driving zonal flow in gas giants
- Meridional Circulation in Solar and Stellar Convection Zones
- A simulation of convective dynamo in the solar convective envelope: maintenance of the solar-like differential rotation and emerging flux
- Stellar Evidence that the Solar Dynamo may be in Transition
- Effects of enhanced stratification on equatorward dynamo wave propagation
- Differential rotation in solar-like stars from global simulations
- Zonal flow regimes in rotating anelastic spherical shells: an application to giant planets
- Dipolar versus multipolar dynamos: the influence of the background density stratification
- Ocean dynamics of outer solar system satellites
- Strong-Field Spherical Dynamos
- Critical Magnetic Prandtl Number for Small-Scale Dynamo
- Magnetically controlled stellar differential rotation near the transition from solar to anti-solar profiles
- Convective Lengthscale in Planetary Cores
- Approaching a realistic force balance in geodynamo simulations
- High-resolution calculation of the solar global convection with the reduced speed of sound technique: II. Near surface shear layer with the rotation
- A Multiscale Dynamo Model Driven by Quasi-geostrophic Convection
- Confirmation of bistable stellar differential rotation profiles
- Force balance in numerical geodynamo simulations: a systematic study
- Powering Stellar Magnetism: Energy Transfers in Cyclic Dynamos of Sun-like Stars
- The Emergence of Solar Supergranulation as a Natural Consequence of Rotationally-Constrained Interior Convection
- Effect of shear and magnetic field on the heat-transfer efficiency of convection in rotating spherical shells
- Transition from axi- to nonaxisymmetric dynamo modes in spherical convection models of solar-like stars
- Zonal flow scaling in rapidly-rotating compressible convection
- Generation solar-like differential rotation
- Near isotropic behaviour of turbulent thermal convection
- Heat transfer and flow regimes in quasi-static magnetoconvection with a vertical magnetic field
- Effects of stratification in spherical shell convection
- Latitudinal regionalization of rotating spherical shell convection
- A Simple Model for Solar Isorotational Contours
- Relating force balances and flow length scales in geodynamo simulations
- A method to discriminate solar and antisolar differential rotation in high-precision light curves
- On the reflection of Alfvén waves and its implication for Earth's core modeling
- The Role of Downflows in Establishing Solar Near-Surface Shear
- Differential Rotation in Magnetized and Non-magnetized Stars
- Sensitivity to luminosity, centrifugal force, and boundary conditions in spherical shell convection
- MRI-driven dynamo at very high magnetic Prandtl numbers
- Revisiting the Sun's Strong Differential Rotation along Radial Lines
- Magnetic effects on fields morphologies and reversals in geodynamo simulations
- Stellar dynamos in the transition regime: multiple dynamo modes and anti-solar differential rotation
- Transition from anti-solar to solar-like differential rotation: Dependence on Prandtl number
- Europa's ocean translates interior tidal heating patterns to the ice-ocean boundary
- Transition from multipolar to dipolar dynamos in stratified systems
- Solenoidal force balances in numerical dynamos
- Solar-like to Antisolar Differential Rotation: A Geometric Interpretation
- A Knee-Point in the Rotation-Activity Scaling of Late-type Stars with a Connection to Dynamo Transitions
- Similarities between characteristics of convective turbulence in confined and extended domains
- Estimation of turbulent diffusivity with direct numerical simulation of stellar convection
- Turbulent Prandtl number from isotropically forced turbulence
- Magnetic field morphologies in convective zones influenced by a turbulent surface layer