Three-dimensional convection simulations of the outer layers of the Sun using realistic physics

Robinson, Franklin; Demarque, P.; Li, L.H.; Sofia, S.; Kim, Y.-C.; Chan, Kalok; Guenther, D. B.

doi:10.1046/j.1365-8711.2003.06349.x

Cited by 93 publications

(107 citation statements)

References 26 publications

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“…These models utilize an extended Kolmogorov spectrum with a modified Gaussian frequency factor. The acoustic energy flux is found to be dependent on the mixinglength parameter α, for which we use α = 2 as indicated by solar studies (Steffen 1993;Robinson et al 2003). Similar investigations in the case of longitudinal flux-tube waves have been presented by Ulmschneider & Musielak (1998).…”

Section: (Magneto-)hydrodynamic Model Computationsmentioning

confidence: 61%

Definition and significance of average temperatures in time-dependent solar chromosphere models

Rammacher¹,

Cuntz

2005

A&A

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Abstract.We assess different types of average temperatures in time-dependent solar chromosphere models. They include the conventional definition of mean and median temperature, and a formal definition related to the model-dependent hydrogen ionization degree, referred to as ionization temperature. It is found that the latter is always higher than the mean and median temperatures, except in the photosphere, and that the mean temperatures are always higher than the median temperatures, especially in models with frequency spectra. The most dramatic differences are attained in the topmost portion of one of our models with the ionization temperatures up to a factor 150 higher than the mean and median temperatures. The differences between the mean, median, and ionization temperatures are a direct consequence of nonlinearities ("spikyness") of the temperatures in the models mostly due to strong shocks. The main results hold for both acoustic and magnetic models despite significant differences in the initial wave energy fluxes, densities, and geometrical settings.

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Section: (Magneto-)hydrodynamic Model Computationsmentioning

confidence: 61%

Definition and significance of average temperatures in time-dependent solar chromosphere models

Rammacher¹,

Cuntz

2005

A&A

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“…The systematic growth in error at higher frequencies (higher n) is associated with the inherent uncertainties in the modeling of the superadiabatic layer of the Sun via the mixing-length theory. Li et al (2002) have shown that much of this discrepancy can be eliminated by incorporating the results of numerical stellar convection in both the model and the p-mode frequency calculation (see also Rosenthal et al 1999;Robinson et al 2003). We assume that the stellar model frequency uncertainties are similar to the discrepancies found between our solar model frequencies and the observed frequencies.…”

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confidence: 59%

Matching Stellar Models to Oscillation Data

Guenther

Brown

2004

ApJ

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We describe a method to match stellar models to a set of low-l p-mode oscillation frequencies. The method provides a quality of fit measure similar to that obtained from a 2 fit. With a sufficiently dense grid of stellar models, the method can determine the best-fitting model to the oscillation data as constrained solely by the oscillation data. That is to say, the method can be used to constrain the mass, age, composition, surface temperature, and luminosity of a star from the oscillation data. We evaluate the method on solar data and apply the method to the recently observed oscillation data for Cen and UMa.

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“…On the other hand, the continuous growth of computer power is allowing us to solve this problem numerically using only the basic laws of hydrodynamics, including radiative transfer in the energy equation. A better understanding of solar and stellar granulation is thus possible through numerical simulations (e.g., Nordlund & Dravins 1990;Freytag et al 1996;Stein & Nordlund 1998;Asplund et al 1999;Ludwig et al 1999;Robinson et al 2003;Vögler 2004;Asplund 2005;Collet et al 2006Collet et al , 2007Nordlund et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Granulation in K-type dwarf stars

Ramírez

Prieto

Koesterke³

et al. 2009

A&A

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Aims. To explore the impact of surface inhomogeneities on stellar spectra, granulation models need to be computed. Ideally, the most fundamental characteristics of these models should be carefully tested before applying them to the study of more practical matters, such as the derivation of photospheric abundances. Our goal is to analyze the particular case of a K-dwarf. Methods. We construct a three-dimensional radiative-hydrodynamic model atmosphere of parameters T eff = 4820 K, log g = 4.5, and solar chemical composition. Using this model and 3D spectrum synthesis, we computed a number of Fe i and Fe ii line profiles.The observations presented in the first paper of this series were used to test the model predictions. The effects of stellar rotation and instrumental imperfections are carefully taken into account in the synthesis of spectral lines. shifts for our reference star, HIP 86 400, shows excellent agreement, with the exception of the core wavelength shifts of the strongest features, for which we suspect inaccurate theoretical values. Since this limitation does not affect the predicted line equivalent widths significantly, we consider our 3D model validated for photospheric abundance work.

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Three-dimensional convection simulations of the outer layers of the Sun using realistic physics

Cited by 93 publications

References 26 publications

Definition and significance of average temperatures in time-dependent solar chromosphere models

Definition and significance of average temperatures in time-dependent solar chromosphere models

Matching Stellar Models to Oscillation Data

Granulation in K-type dwarf stars

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