SIMULATION OF THE FORMATION OF A SOLAR ACTIVE REGION

Journal Article · Wed Sep 01 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/720/1/233· OSTI ID:21460135

Cheung, M C. M.; Title, A M ^[1]; Rempel, M ^[2]; Schuessler, M ^[3]

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1. Lockheed Martin Solar and Astrophysics Laboratory, Palo Alto, CA 94304 (United States)
2. High Altitude Observatory, NCAR, P.O. Box 3000, Boulder, CO 80307 (United States)
3. Max Planck Institute for Solar System Research, Katlenburg-Lindau, 37191 (Germany)

We present a radiative magnetohydrodynamics simulation of the formation of an active region (AR) on the solar surface. The simulation models the rise of a buoyant magnetic flux bundle from a depth of 7.5 Mm in the convection zone up into the solar photosphere. The rise of the magnetic plasma in the convection zone is accompanied by predominantly horizontal expansion. Such an expansion leads to a scaling relation between the plasma density and the magnetic field strength such that B {proportional_to} rhov{sup 1/2}. The emergence of magnetic flux into the photosphere appears as a complex magnetic pattern, which results from the interaction of the rising magnetic field with the turbulent convective flows. Small-scale magnetic elements at the surface first appear, followed by their gradual coalescence into larger magnetic concentrations, which eventually results in the formation of a pair of opposite polarity spots. Although the mean flow pattern in the vicinity of the developing spots is directed radially outward, correlations between the magnetic field and velocity field fluctuations allow the spots to accumulate flux. Such correlations result from the Lorentz-force-driven, counterstreaming motion of opposite polarity fragments. The formation of the simulated AR is accompanied by transient light bridges between umbrae and umbral dots. Together with recent sunspot modeling, this work highlights the common magnetoconvective origin of umbral dots, light bridges, and penumbral filaments.

• OSTI ID: 21460135
• Journal Information: Astrophysical Journal, Vol. 720, Issue 1; Other Information: DOI: 10.1088/0004-637X/720/1/233; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

30 DIRECT ENERGY CONVERSION
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
CONVECTION
LORENTZ FORCE
MAGNETIC FIELDS
MAGNETIC FLUX
MAGNETOHYDRODYNAMICS
PHOTOSPHERE
PLASMA DENSITY
SIMULATION
SUN
SUNSPOTS
ATMOSPHERES
ENERGY TRANSFER
FLUID MECHANICS
HEAT TRANSFER
HYDRODYNAMICS
MAIN SEQUENCE STARS
MASS TRANSFER
MECHANICS
SOLAR ACTIVITY
SOLAR ATMOSPHERE
STARS
STARSPOTS
STELLAR ACTIVITY
STELLAR ATMOSPHERES