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The interpretation of total line intensities from optically thin gases

Research paper by J. T. Jefferies, F. Q. Orrall, J. B. Zirker

Indexed on: 01 Feb '72Published on: 01 Feb '72Published in: Solar Physics



Abstract

We describe a general method for inferring, from the line emission of an optically thin medium, the physical state of the gas along the column in the line of sight which is sampled by the observations. Since it is not possible to infer the distribution of the physical state parameters with position in the line of sight - any arbitrary rearrangement of material giving equivalent line emission - we seek instead to specify the state in another way. A unique specification is found in terms of the bivariate distribution function μ (n, T), describing the partitioning of the matter in the gas over the density and temperature. We show that, given sufficient observational data, it is in principle possible to determine both μ (n, T), and the chemical composition. With less complete data the acuity of the analysis is correspondingly reduced.The method is devised for application to the astronomical case, especially for studies of the solar corona, the chromosphere-corona transition region, planetary nebulae and other optically thin sources. We illustrate the formulation for the situation encountered in the solar corona.