Non-LTE line transfer with convective transport of excited atoms.
Abstract
Convective transport of excited atoms in a homogeneous medium containing two-level atoms is considered. This physical effect necessarily occurs whenever radiative line transfer takes place in non-LTE situations, in astrophysical as well as laboratory plasmas. It is argued that, in physical terms, neglecting this effect is tantamount to using a model in which particle number is not conserved. Evidence is given to show that a diffusion model for convective transport of excited atoms has rather limited applicability since, in a diffusion regime, the diffusion flow usually has a negligible effect on non-LTE-line transfer. It is suggested on physical grounds that solutions to the non-LTE line-transfer problem in the case of a kinetic regime should depend rather sensitively on the boundary conditions imposed on the excited-atom gas.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- July 1979
- Bibcode:
- 1979A&A....76..312O
- Keywords:
-
- Atomic Excitations;
- Convective Flow;
- Line Spectra;
- Radiative Transfer;
- Stellar Atmospheres;
- Atomic Collisions;
- Diffusion Theory;
- Elastic Scattering;
- Helium;
- Hydrogen;
- Kinetic Equations;
- Thermodynamic Equilibrium;
- Astrophysics;
- Radiative Transfer:Stellar Atmospheres