On the inference of differential emission measures using diagnostic line ratios

Spectroscopic diagnosis of hot optically thin plasmas can be used to infer valuable information about the temperature structure of the emitting plasma volume, through the emission measure differential (DEM) in T_e, DEM(T_e). However, the uncertainties in atomic parameters (required to model the plasma emission) make such inferences intractable. We demonstrate that it is possible, and relatively straightforward, to implement a formalism and infer DEM(T_e) in a way such that atomic uncertainties are treated explicitly. Indeed, we show that a hybrid line-ratio/emission-measure method is robust when "standard" inversion methods will fail to produce consistent results.