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<b>ASTRONOMY COLLOQUIUM</b><br>The Effects of Magnetic Field Morphology on the Determination of Oxygen and Iron Abundances in the Solar Photosphere

Tuesday, October 20, 2015
12:00 AM
411 West Hall

The solar chemical abundance (or a scaled version of it) is implemented in numerous astrophysical analyses. Thus, an accurate and precise estimation of the solar elemental abundance is crucial in astrophysics. We have explored the impact of magnetic fields on the determination of the solar photospheric oxygen and iron abundances using 3D radiation–magnetohydrodynamic (MHD) simulations of convection. Specifically, we examined differences in abundance deduced from three classes of atmospheres simulated with the MURaM code: a pure hydrodynamic (HD) simulation, an MHD simulation with a local dynamo magnetic field that has saturated with an unsigned vertical field strength of 80 G at the optical depth unity surface, and an MHD simulation with an initially imposed vertical mean field of 80 G. We use differential equivalent width analysis for diagnosing abundances derived from five oxygen and four iron spectral lines of differing wavelength, oscillator strength, excitation potential, and Lande g-factor, and find that the morphology of the magnetic field is important to the outcome of abundance determinations. The largest deduced abundance differences are found in the vertical mean field simulations and small scale unresolved field resulting from the local dynamo has a smaller impact on abundance determinations.