A solar surface dynamo

By A. Voegler, M. Schüssler. 2007

251 citations recorded by the source corpus.

Context. Observations indicate that the “quiet” solar photosphere outside active regions contains considerable amounts of magnetic energy and magnetic flux, with mixed polarity on small scales. The origin of this flux is unclear. Aims. We test whether local dynamo action of the near-surface convection (granulation) can generate a significant contribution to the observed magnetic flux. Methods. We have carried out MHD simulations of solar surface convection, including the effects of strong stratification, compressibility, partial ionization, radiative transfer, as well as an open lower boundary. Results. Exponential growth of a weak magnetic seed field (with vanishing net flux through the computational box) is found in a simulation run with a magnetic Reynolds number of about 2600. The magnetic energy approaches saturation at a level of a few percent of the total kinetic energy of the convective motions. Near the visible solar surface, the (unsigned) magnetic flux density reaches at least a value of about 25 G. Conclusions. A realistic flow topology of stratified, compressible, non-helical surface convection without enforced recirculation is capable of turbulent local dynamo action near the solar surface.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/d822e00cb1eacd88343793752efa2b20415e8fcc

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Citations in the corpus

NUMERICAL SIMULATIONS OF QUIET SUN MAGNETISM: ON THE CONTRIBUTION FROM A SMALL-SCALE DYNAMO (2014, methodology): “The boundary condition OV is similar to that used by Vögler & Schüssler (2007) and we included one simulation with this boundary condition to better connect our results to previous work.”
Sunrise: INSTRUMENT, MISSION, DATA, AND FIRST RESULTS (2010, methodology): “The Sunrise/IMaX Stokes-V movie displays qualitative similarities to movies of the vertical magnetic field in turbulent dynamo simulations (Vögler and Schüssler 2007), although both the spatial and the temporal scales are quite different.”
Solar Orbiter (2012, background): “MHD simulations indicate that a local turbulent dynamo should be acting in the Sun’s turbulent convection zone (Brun, Miesch, and Toomre, 2004) and even in the near-surface layers (Vögler and Schüssler, 2007).”
ORBITAL MOTION OF HR 8799 b, c, d USING HUBBLE SPACE TELESCOPE DATA FROM 1998: CONSTRAINTS ON INCLINATION, ECCENTRICITY, AND STABILITY (2011, background): “Modern models of the small-scale turbulent dynamo in the photosphere (Boldyrev & Cattaneo 2004; V¨ogler & Sch¨ussler 2007; Pietarila Graham et al. 2009) utilize the collisional value of magnetic diﬀusivity (0.01 - 10 km 2 s − 1 ) based on the electric conductivity in the photosphere.”
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).”
Solar Surface Emerging Flux Regions: A Comparative Study of Radiative MHD Modeling and Hinode SOT Observations (2008, methodology): “…2006), solar pores (Cameron et al. 2007), the photospheric reversed granulation (Cheung, Schüssler, & Moreno-Insertis 2007b), the solar surface dynamo (Vögler & Schüssler 2007; Schüssler & Vögler 2008) and, as a predecessor to the present study, magnetic flux emergence in granular convection…”
Solar Dynamo Theory (2014, background): “A turbulent flow can generate strong magnetic fields on its own small spatial scale provided Rm is large enough (see, e.g., Cattaneo 1999, Cattaneo et al. 2003, Stein & Nordlund 2006, Vögler & Schüssler 2007).”