SIMULATION OF THE FORMATION OF A SOLAR ACTIVE REGION

By Mark C. M. Cheung, Matthias Rempel, A. Title, M. Schüssler. 2010

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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 ∝ ϱ1/2. 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.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/d613f947fbf7aae7ad4fa40cf9a3502724d31038

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In Astronomy and Astrophysics

Citations in the corpus

THE CENTRAL MOLECULAR GAS STRUCTURE IN LINERS WITH LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI: EVIDENCE FOR GRADUAL DISAPPEARANCE OF THE TORUS (2012, background): “D MHD simulations) to explore the formation of pores and sunspots (e.g. Cheung et al. 2010; also see review by Stein 2012), although the spatial domain achieved so far is still very small (the “deepest” simulations go down to a depth of 20Mm).”
Magnetic Flux Transport at the Solar Surface (2014, background): “The emergence processes have been modeled in detail for bothlarge-scale active regions (e.g., Cheung et al. 2008, 2010; Stein et al. 2011) and for the smallscale dynamo processes (Vögler and Schüssler 2007; Schüssler and Vögler 2008).”