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Title: SIMULATION OF THE FORMATION OF A SOLAR ACTIVE REGION

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 andmore » umbral dots. Together with recent sunspot modeling, this work highlights the common magnetoconvective origin of umbral dots, light bridges, and penumbral filaments.« less
Authors:
;  [1] ;  [2] ;  [3]
  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)
Publication Date:
OSTI Identifier:
21460135
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 720; Journal Issue: 1; Other Information: DOI: 10.1088/0004-637X/720/1/233
Country of Publication:
United States
Language:
English
Subject:
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