BUOYANT MAGNETIC LOOPS IN A GLOBAL DYNAMO SIMULATION OF A YOUNG SUN

Journal Article · Sat Oct 01 00:00:00 EDT 2011 · Astrophysical Journal Letters

DOI:https://doi.org/10.1088/2041-8205/739/2/L38· OSTI ID:21565440

Nelson, Nicholas J; Toomre, Juri ^[1]; Brown, Benjamin P ^[2]; Brun, Allan Sacha ^[3]; Miesch, Mark S ^[4]

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1. JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309-0440 (United States)
2. Department of Astronomy and Center for Magnetic Self-Organization (CSMO) in Laboratory and Astrophysical Plasmas, University of Wisconsin, Madison, WI 53706-1582 (United States)
3. Laboratoire AIM Paris-Saclay, CEA/Irfu Universite Paris-Diderot CNRS/INSU, 91191 Gif-sur-Yvette (France)
4. High Altitude Observatory, NCAR, Boulder, CO 80307-3000 (United States)

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 starspots 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 three-dimensional 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.

• OSTI ID: 21565440
• Journal Information: Astrophysical Journal Letters, Vol. 739, Issue 2; Other Information: DOI: 10.1088/2041-8205/739/2/L38; ISSN 2041-8205
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CONVECTION
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
PHOTOSPHERE
SIMULATION
STRATIFICATION
SUN
SUNSPOTS
THREE-DIMENSIONAL CALCULATIONS
TURBULENCE
ATMOSPHERES
ENERGY TRANSFER
FLUID MECHANICS
HEAT TRANSFER
HYDRODYNAMICS
MAIN SEQUENCE STARS
MASS TRANSFER
MECHANICS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
STARS
STARSPOTS
STELLAR ACTIVITY
STELLAR ATMOSPHERES