Stellar Dynamos with Solar and Anti-solar Differential Rotations: Implications to Magnetic Cycles of Slowly Rotating Stars

Abstract

Simulations of magnetohydrodynamics convection in slowly rotating stars predict anti-solar differential rotation (DR) in which the equator rotates slower than poles. This anti-solar DR in the usual $\alpha \Omega$ dynamo model does not produce polarity reversal. Thus, the features of large-scale magnetic fields in slowly rotating stars are expected to be different than stars having solar-like DR. In this study, we perform mean-field kinematic dynamo modelling of different stars at different rotation periods. We consider anti-solar DR for the stars having rotation period larger than 30~days and solar-like DR otherwise. We show that with particular $\alpha$ profiles, the dynamo model produces magnetic cycles with polarity reversals even with the anti-solar DR provided, the DR is quenched when the toroidal field grows considerably high and there is a sufficiently strong $\alpha$ for the generation of toroidal field. Due to the anti-solar DR, the model produces an abrupt increase of magnetic field exactly when the DR profile is changed from solar-like to anti-solar. This enhancement of magnetic field is in good agreement with the stellar observational data as well as some global convection simulations. In the solar-like DR branch, with the decreasing rotation period, we find the magnetic field strength increases while the cycle period shortens. Both of these trends are in general agreement with observations. Our study provides additional support for the possible existence of anti-solar DR in slowly rotating stars and the presence of unusually enhanced magnetic fields and possibly cycles which are prone to production of superflare.

Accepted for publication in MNRAS

References in corpus (23)

• Toroidal versus poloidal magnetic fields in Sun-like stars: a rotation threshold
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• Generalized investigation of the rotation-activity relation: Favouring rotation period instead of Rossby number
• Solar-type dynamo behaviour in fully convective stars without a tachocline
• The crucial role of surface magnetic fields for the solar dynamo
• Solar Cycle Propagation, Memory, and Prediction: Insights from a Century of Magnetic Proxies
• 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
• Rapidly Rotating Suns and Active Nests of Convection
• Importance of Meridional Circulation in Flux Transport Dynamo: The Possibility of a Maunder-like Grand Minimum
• Magnetically controlled stellar differential rotation near the transition from solar to anti-solar profiles
• Solar rotation rate and its gradients during cycle 23
• Simulations of turbulent convection in rotating young solar-like stars: Differential rotation and meridional circulation
• The Waldmeier effect and the flux transport solar dynamo
• A Survey of Chromospheric Activity in the Solar-Type Stars in the Open Cluster M67
• Polar Network Index as a magnetic proxy for the solar cycle studies
• Quenching and anisotropy of hydromagnetic turbulent transport
• A method to discriminate solar and antisolar differential rotation in high-precision light curves
• How does the shape and thickness of the tachocline affect the distribution of the toroidal magnetic fields in the solar dynamo?
• Anti-solar differential rotation on the active sub-giant HU Virginis
• Waldmeier Effect in Stellar Cycles
• Antisolar differential rotation with surface lithium enrichment on the single K-giant V1192 Orionis
• Solar-cycle variation of the rotational shear near the solar surface

Cited by in corpus (7)

• Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution
• Waldmeier Effect in Stellar Cycles
• Dynamo modelling for cycle variability and occurrence of grand minima in Sun-like stars: Rotation rate dependence
• Wavelet analysis of the long-term activity of V833 Tau
• The Hot Neptune WASP-166~b with ESPRESSO I: Refining the Planetary Architecture and Stellar Variability
• WASP-131 b with ESPRESSO I: A bloated sub-Saturn on a polar orbit around a differentially rotating solar-type star
• Hunting for anti-solar differentially rotating stars using the Rossby number -- An application to the Kepler field