Line radiation effects in laboratory and astrophysical plasmas

Theoretical enhancement of line radiation above the optically thin limit has been previously noted to occur in solar and stellar coronal plasmas, but presented without clear physical explanation. Here, we give an analysis of the angular dependence of these radiative transfer effects, which explain the previously calculated but poorly understood line radiation intensity enhancements. There are two important ramifications of this analysis: firstly, it provides a reason for the indeterminate status of opacity in relation to the coronal lines of distant stellar sources-hence potentially solving an important problem in astrophysics; secondly, it provides the opportunity to derive geometric information from the spectrum of a spatially unresolvable stellar object. We discuss the potential for observation of such opacity enhancement effects in laser plasmas, and present a feasibility study for experiments of this type.