Magnetic flux emergence in granular convection: radiative MHD simulations and observational signatures

By Mark C. M. Cheung, Manfred SchuesslerFernando Moreno-Insertis. 2007

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Aims. We study the emergence of magnetic flux from the near-surface layers of the solar convection zone into the photosphere. Methods. To model magnetic flux emergence, we carried out a set of numerical radiative magnetohydrodynamics simulations. Our simulations take into account the effects of compressibility, energy exchange via radiative transfer, and partial ionization in the equation of state. All these physical ingredients are essential for a proper treatment of the problem. Furthermore, the inclusion of radiative transfer allows us to directly compare the simulation results with actual observations of emerging flux. Results. We find that the interaction between the magnetic flux tube and the external flow field has an important influence on the emergent morphology of the magnetic field. Depending on the initial properties of the flux tube (e.g. field strength, twist, entropy etc.), the emergence process can also modify the local granulation pattern. The emergence of magnetic flux tubes with a flux of 10 19 Mx disturbs the granulation and leads to the transient appearance of a dark lane, which is coincident with upflowing material. These results are consistent with observed properties of emerging magnetic flux.

Subfields: Astronomy and Astrophysics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/2b9a0e79a485c347050c7a9975e0180d1a96daaa

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Citations in the corpus

Solar Surface Emerging Flux Regions: A Comparative Study of Radiative MHD Modeling and Hinode SOT Observations (2008, methodology): “In Cheung et al. (2007a), we presented a study of magnetic flux emergence in granular convection by means of numerical radiative MHD simulations with the MURaM code (Vögler et al. 2005).”
The Solar Optical Telescope for the Hinode Mission: An Overview (2007, background): “…with the SOT, interaction with numerical simulations becomes critically important for the quiet sun (Khomenko et al., 2005), for emerging flux (Cheung, Schüssler, and Moreno-Insertis, 2007), for chromospheric waves (Skartlien, Stein, and Nordlund, 2000), and for corona-chromospheric…”
Emergence of Small-Scale Magnetic Loops in the Quiet-Sun Internetwork (2007, background): “This is in agreement with the simulations presented in Cheung et al (2007), where small-scale flux tubes with less than 1018 Mx of longitudinal flux are not sufficiently buoyant to rise coherently against the granulation, and produce no visible disturbances in it.”
Emergence of a Helical Flux Rope under an Active Region Prominence (2008, background): “Cheung et al. (2007) observed similar polarity reversal in their radiative MHD simulation.”
SIMULATION OF THE FORMATION OF A SOLAR ACTIVE REGION (2010, background): “…terms in the energy equation) have shown these two effects to be very important to the properties of flux emergence (Stein & Nordlund 2006; Cheung et al. 2007, 2008; Isobe et al. 2008; Abbett 2007; Mart́ınez-Sykora et al. 2008, 2009; Tortosa-Andreu & Moreno-Insertis 2009; Yelles Chaouche…”
The Magnetic Connection between the Convection Zone and Corona in the Quiet Sun (2007, background): “Third, like the simulations of Cheung et al. (2007b), each run exhibits a temperature reversal of the convective pattern with height in the chromosphere (see the right column of Figs.”