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 Å 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 \log \epsilon ( { C } ) = 8.39 \pm 0.04 dex .
Combining this result with our parallel analysis of the [ O I ] 6300 Å line , we find C/O = 0.50 \pm 0.07 , in agreement with the ratios measured in the solar corona from gamma-ray spectroscopy and solar energetic particles .

Subject headings : convection — line : formation — Sun : abundances — Sun : photosphere