A Reappraisal of the Solar Photospheric C/O Ratio

Abstract

An accurate determination of photospheric solar abundances requires detailed modeling of the solar granulation and accounting for departures from local thermodynamical equilibrium (LTE). We argue that the forbidden C i line at 8727 A is largely immune to departures from LTE and can be realistically modeled using LTE radiative transfer in a time-dependent three-dimensional simulation of solar surface convection. We analyze the [C i] line in the solar flux spectrum to derive the abundance dex. Combining this result with our log e(C) p 8.39 0.04 parallel analysis of [O i] l6300, we find , in agreement with the ratios measured in the solar C/O p 0.50 0.07 corona from gamma-ray spectroscopy and solar energetic particles.