Effects of Chemical Abundances on the Structure and Dynamics of the Solar Atmosphere

This paper presents a comparison between two three-dimensional radiative hydrodynamical (3D RHD) simulations of the solar outer layers using the Grevesse & Sauval (1998; GS98) and the Asplund, Grevesse & Sauval (2005; AGS05) mixtures, respectively.The AGS05 mixture is a revision of the solar abundance mixture using a model atmosphere based on the stratification and dynamics of a solar 3D RHD simulation performed with the GS98 mixture, using the code of Stein & Nordlund (1989, 1998). Our simulations use the same code, and physically realistic treatment of radiative opacities and equation of state as Robinson et al. (2003).A comparison between our GS98 and AGS05 3D simulations shows differences both in the mean vertical temperature gradient and in the turbulent velocity field in the line forming region of the solar atmosphere. The whole superadiabatic layer (SAL) in the AGS05 simulation, including its peak, is shifted outward with respect to the GS98 SAL. Turbulent velocities, critical for absorption line profile calculations, are larger in the AGS05 simulation by about 10%. Since opacities for the AGS05 mixture are lower than those for the GS98 mixture, the T-? relations derived from the two simulations are different. At 5000K, ? obtained from the GS98 simulation is about 30% larger than that obtained from the AGS05 simulation.These results show the importance of preserving self consistency in the chemical abundances between the model atmosphere and the 3D HRD simulation. When deriving the solar abundances, one must iterate the chemical composition in the model atmosphere, and hence in the 3D simulation on which the atmosphere is based.