The Effect of Velocity Gradients on Multi-level Atom Non-LTE Line Source Functions

Abstract

Macroscopic velocity gradients are featured in calculations of several different line source functions for a model multi-level atom in non-LTE. The physical processes giving rise to these source functions, and their corresponding line profiles, are discussed in detail. In particular, three quite distinct coupling mechanisms between the various levels in the atom are considered and the results so obtained enable an easy interpretation of non-LTE line source functions to be made for any multilevel atom.