Buoyant Magnetic Loops in a Global Dynamo Simulation of a Young Sun

Abstract

The current dynamo paradigm for the Sun and sun-like stars places the generation site for strong toroidal magnetic structures deep in the solar interior. Sunspots and star-spots on sun-like stars are believed to arise when sections of these magnetic structures become buoyantly unstable and rise from the deep interior to the photosphere. Here we present the first 3-D global magnetohydrodynamic (MHD) simulation in which turbulent convection, stratification, and rotation combine to yield a dynamo that self-consistently generates buoyant magnetic loops. We simulate stellar convection and dynamo action in a spherical shell with solar stratification, but rotating three times faster than the current solar rate. Strong wreaths of toroidal magnetic field are realized by dynamo action in the convection zone. By turning to a dynamic Smagorinsky model for subgrid-scale turbulence, we here attain considerably reduced diffusion in our simulation. This permits the regions of strongest magnetic field in these wreaths to rise toward the top of the convection zone via a combination of magnetic buoyancy instabilities and advection by convective giant cells. Such a global simulation yielding buoyant loops represents a significant step forward in combining numerical models of dynamo action and flux emergence.

6 pages, 3 figures, accepted in ApJ Letters

References in corpus (6)

• Global-Scale Turbulent Convection and Magnetic Dynamo Action in the Solar Envelope
• Toroidal versus poloidal magnetic fields in Sun-like stars: a rotation threshold
• Persistent Magnetic Wreaths in a Rapidly Rotating Sun
• Magnetic Cycles in a Convective Dynamo Simulation of a Young Solar-type Star
• Dynamo action and magnetic buoyancy in convection simulations with vertical shear
• The Nonlinear Evolution of Instabilities Driven by Magnetic Buoyancy: A New Mechanism for the Formation of Coherent Magnetic Structures

Cited by in corpus (40)

• Flare-productive active regions
• Generalized investigation of the rotation-activity relation: Favouring rotation period instead of Rossby number
• Magnetic Wreaths and Cycles in Convective Dynamos
• A simulation of convective dynamo in the solar convective envelope: maintenance of the solar-like differential rotation and emerging flux
• Deciphering Solar Magnetic Activity I: On The Relationship Between The Sunspot Cycle And The Evolution Of Small Magnetic Features
• Buoyant Magnetic Loops Generated by Global Convective Dynamo Action
• Emergence of magnetic flux generated in a solar convective dynamo. I: Formation of Sunspots and Active regions, and Origin of Their Asymmetries
• Energy Conservation and Gravity Waves in Sound-proof Treatments of Stellar Interiors: Part I Anelastic Approximations
• The Solar-Stellar Connection
• Rieger-type periodicity during solar cycles 14-24: estimation of dynamo magnetic field strength in the solar interior
• Comparing Simulations of Rising Flux Tubes Through the Solar Convection Zone with Observations of Solar Active Regions: Constraining the Dynamo Field Strength
• Emergence of granular-sized magnetic bubbles through the solar atmosphere: I. Spectropolarimetric observations and simulations
• Large-Eddy Simulations of Magnetohydrodynamic Turbulence in Heliophysics and Astrophysics
• Kinematic active region formation in a three-dimensional solar dynamo model
• On the sensitivity of magnetic cycles in global simulations of solar-like stars
• Global Dynamics of Subsurface Solar Active Regions
• Magnetic Flux Emergence and Decay Rates for Preceder and Follower Sunspots Observed with HMI
• $\delta$-Sunspot Formation in Simulation of Active-Region-Scale Flux Emergence
• Theoretical limits on magnetic field strengths in low-mass stars
• Effects of a subadiabatic layer on convection and dynamos in spherical wedge simulations
• Flux emergence in a magnetized convection zone
• Spherical-shell boundaries for two-dimensional compressible convection in a star
• Ejections of magnetic structures above a spherical wedge driven by a convective dynamo with differential rotation
• Magnetic flux concentrations from dynamo-generated fields
• Bipolar region formation in stratified two-layer turbulence
• A Theory on the Convective Origins of Active Longitudes on Solar-like Stars
• Modeling Repeatedly Flaring $\delta$ Sunspots
• Modeling the Rise of Fibril Magnetic Fields in Fully Convective Stars
• Motivation and challenge to capture both large scale and local transport in next generation accretion theory
• Convective Babcock-Leighton Dynamo Models
• Probing the Influence of a Tachocline in Simulated M-Dwarf Dynamos
• Exploring Bistability in the Cycles of the Solar Dynamo through Global Simulations
• On the origin of the solar hemispherical helicity rules: Simulations of the rise of magnetic flux concentrations in a background field
• Cinematic Visualization of Multiresolution Data: Ytini for Adaptive Mesh Refinement in Houdini
• Longitudinally Modulated Dynamo Action in Simulated M-Dwarf Stars
• Three-dimensional non-kinematic simulation of post-emergence evolution of bipolar magnetic regions and Babcock-Leighton dynamo of the Sun
• Generating buoyant magnetic flux ropes in solar-like convective dynamos
• Low-latitude magnetic flux emergence on rapidly rotating solar-type stars
• Dynamos and Differential Rotation: Advances at the Crossroads of Analytics, Numerics, and Observations
• The Suppression and Promotion of Magnetic Flux Emergence in Fully Convective Stars