The 2D dynamics of radiative zones of low-mass stars

Abstract

In the context of secular evolution, we describe the dynamics of the radiative core of low-mass stars to understand the internal transport of angular momentum in such stars which results in a solid rotation in the Sun from 0.7R_sun to 0.2R_sun and a weak radial core-envelope differential rotation in solar-type stars. This study requires at least a 2D description to capture the latitudinal variations of the differential rotation. We build 2D numerical models of a radiative core on the top of which we impose a latitudinal shear so as to reproduce a cylindrical differential rotation in a convective envelope. We perform a systematic study over the Rossby number measuring the latitudinal differential rotation at the radiative-convective interface. The imposed shear generates a geostrophic flow implying a cylindrical differential rotation. When compared to the baroclinic flow that arises from the stable stratification, we find that the geostrophic flow is dominant when the Rossby number is high enough with a cylindrical rotation profile. For low Rossby numbers, the baroclinic solution dominates with a quasi-shellular rotation profile. Using scaling laws from 3D simulations, we show that slow rotators are expected to have a cylindrical rotation profile. Fast rotators may have a shellular profile at the beginning of the main-sequence in stellar radiative zones. This study enables us to predict different types of differential rotation and emphasizes the need of a new generation of 2D rotating stellar models developed in synergy with 3D numerical simulations. The shear induced by a surface convective zone has a strong impact on the dynamics of the underlying radiative zone in low-mass stars. But, it cannot produce a flat internal rotation profile in a solar configuration calling for additional processes for the transport of angular momentum in both radial and latitudinal directions.

12 pages, 7 figures, accepted for publication in A&A

References in corpus (18)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Global-Scale Turbulent Convection and Magnetic Dynamo Action in the Solar Envelope
• Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars
• The effect of magnetic topology on thermally-driven winds: towards a general formulation of the braking law
• Improved angular momentum evolution model for solar-like stars II. Exploring the mass dependence
• On differential rotation and overshooting in solar-like stars
• Rapidly Rotating Suns and Active Nests of Convection
• Magnetic confinement of the solar tachocline
• Rotating models of young solar-type stars : Exploring braking laws and angular momentum transport processes
• Diagnoses to unravel secular hydrodynamical processes in rotating main sequence stars
• Measuring the extent of convective cores in low-mass stars using Kepler data: towards a calibration of core overshooting
• Magnetic confinement of the solar tachocline: II. Coupling to a convection zone
• The Solar-Stellar Connection
• The dynamics of the radiative envelope of rapidly rotating stars. I. A spherical Boussinesq model
• A Simple Model for Solar Isorotational Contours
• Characterizing the feedback of magnetic field on the differential rotation of solar-like stars
• Dynamics of the radiative envelope of rapidly rotating stars: Effects of spin-down driven by mass loss
• Dynamics of the envelope of a rapidly rotating star or giant planet in gravitational contraction

Cited by in corpus (3)

• First grids of low-mass stellar models and isochrones with self-consistent treatment of rotation : From 0.2 to 1.5 M_\odot at 7 metallicities from PMS to TAMS
• Horizontal shear instabilities in rotating stellar radiation zones: II. Effects of the full Coriolis acceleration
• Stress-driven spin-down of a viscous fluid within a spherical shell