Differential Rotation in Magnetized and Non-magnetized Stars

Abstract

Effects of magnetic field on stellar differential rotation are studied by comparing magnetohydrodynamic (MHD) models and their hydrodynamic (HD) counterparts in the broad range of rotation rate and in varying initial rotation profile. Fully-compressible MHD simulations of rotating penetrative convection are performed in a full-spherical shell geometry. Critical conditions for the transition of the differential rotation between faster equator (solar-type) and slower equator (anti-solar type) are explored with focusing on the "Rossby number ($\mathrm{Ro}$)" and the "convective Rossby number (${\mathrm{Ro}}_{\mathrm{conv}}$)". It is confirmed that the transition is more gradual and the critical value for it is higher in the MHD model than the HD model in the view of the ${\mathrm{Ro}}_{\mathrm{conv}}$-dependence. The rotation profile shows, as observed in earlier studies, the bistability near the transition in the HD model, while it disappears when allowing the growth of magnetic fields except for the model with taking anti-solar type solution as the initial condition. We find that the transition occurs at $\mathrm{Ro}\simeq 1$ both in the MHD and HD models independently of the hysteresis. Not only the critical value, the sharpness of the transition is also similar between the two models in the view of the $\mathrm{Ro}$-dependence. The influences of the dynamo-generated magnetic field and/or the hysteresis on convective motion are reflected in the $\mathrm{Ro}$. This would be the reason why the transition is unified in the view of the $\mathrm{Ro}$-dependence. We finally discuss the $\mathrm{Ro}$-dependence of magnetic dynamo activities with emphasis on its possible relation to the kinetic helicity profile.

arXiv comment16 pages, 12 figures, Accepted for publication in ApJ

References in corpus (29)

• Global-Scale Turbulent Convection and Magnetic Dynamo Action in the Solar Envelope
• The "Yin-Yang Grid": An Overset Grid in Spherical Geometry
• Solar Interior Rotation and its Variation
• Simulations of dynamo action in fully convective stars
• Detection of Equatorward Meridional Flow and Evidence of Double-Cell Meridional Circulation inside the Sun
• Turbulent Convection Under the Influence of Rotation: Sustaining a Strong Differential Rotation
• Solar differential rotation and meridional flow: The role of a subadiabatic tachocline for the Taylor-Proudman balance
• Magnetic Cycles in a Convective Dynamo Simulation of a Young Solar-type Star
• From solar-like to anti-solar differential rotation in cool stars
• The Sun in Time: Activity and Environment
• Observations of Cool-Star Magnetic Fields
• Current status of turbulent dynamo theory: From large-scale to small-scale dynamos
• A simulation of convective dynamo in the solar convective envelope: maintenance of the solar-like differential rotation and emerging flux
• The asteroseismic potential of Kepler: first results for solar-type stars
• Solar Meridional Circulation from Doppler Shifts of the Fe I line at lambda 5250 Angstroms as Measured by the 150-foot Solar Tower Telescope at the Mt. Wilson Observatory
• Effects of enhanced stratification on equatorward dynamo wave propagation
• Differential rotation in solar-like stars from global simulations
• Dipole Collapse and Dynamo Waves in Global Direct Numerical Simulations
• Zonal flow regimes in rotating anelastic spherical shells: an application to giant planets
• A study of possible temporal and latitudinal variations in the properties of the solar tachocline
• Confirmation of bistable stellar differential rotation profiles
• Large-scale dynamos in rigidly rotating turbulent convection
• Torsional Oscillations in a Global Solar Dynamo
• Oscillatory migrating magnetic fields in helical turbulence in spherical domains
• Effects of stratification in spherical shell convection
• Effects of Penetrative Convection on Solar Dynamo
• Impact of MHD Turbulence on Thermal Wind Balance in the Sun
• Mean-Field Modeling of ${\alpha }^2$-Dynamo Coupled with Direct Numerical Simulations of Rigidly Rotating Convection
• Long-term Evolution of Large-scale Magnetic Fields in Rotating Stratified Convection

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• On the sensitivity of magnetic cycles in global simulations of solar-like stars
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• Evolution of solar and stellar dynamo theory
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• Angular Momentum Transport in Proto-Neutron Stars and the Fate of Neutron Star Merger Remnants
• Sensitivity to luminosity, centrifugal force, and boundary conditions in spherical shell convection
• Dynamo Effects Near The Transition from Solar to Anti-Solar Differential Rotation
• Convection and Dynamo in Newly-born Neutron Stars
• Stellar dynamos in the transition regime: multiple dynamo modes and anti-solar differential rotation
• Driving Solar Giant Cells through the Self-Organization of Near-Surface Plumes
• Solar-like to Antisolar Differential Rotation: A Geometric Interpretation
• Differential Rotation in a 3D Simulation of Oxygen Shell Burning
• Hunting for anti-solar differentially rotating stars using the Rossby number -- An application to the Kepler field
• Convective Differential Rotation in Stars and Planets I: Theory
• Lorentz force mediation of turbulent dynamo transitions
• Polar waves and chaotic flows in thin rotating spherical shells
• Convective Differential Rotation in Stars and Planets II: Observational and Numerical Tests
• Differential Rotation in Solar Convective Dynamo Simulations
• Impacts of small-scale dynamo on rotating columnar convection in stellar convection zones