Abstract
We present a diffusion equation (FDT) with a coefficient that reduces to the appropriate limiting form in the streaming and near thermodynamic limits for a moving fluid in which the dominant source of opacity is Thomson scattering. This expression, derived from the general diffusion theory of Levermore & Pomraning and Pomraning, is fully flux-limited, and is useful for the radiative-hydrodynamical simulation of scattering media such as accretion-disk coronae. We compare our results to those obtained with the corresponding equations for an absorptive medium, and we show that the flux can differ by a large factor (≫ 1) between the two, depending on the temperature profile within the atmosphere. A direct comparison of our equations with exact solutions of the transfer equation suggests that FDT for a scattering medium is accurate to better than ≲ 17% over the range of optical depths 0 ≲τ ≲ 3.
Original language | English (US) |
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Pages (from-to) | 732-740 |
Number of pages | 9 |
Journal | Astrophysical Journal |
Volume | 374 |
Issue number | 2 |
DOIs | |
State | Published - Jun 20 1991 |
Externally published | Yes |
Keywords
- Diffusion
- Radiative transfer
- Stars: accretion
- Stars: binaries
- Stars: coronae
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science