Simultaneous temperature and density diagnostics of optically thin plasmas

A method is given for performing simultaneous temperature and density diagnostics of an optically thin plasma by means of all the available observations of lines of the same ions. The density and differential emission measure at selected temperatures may be measured and the chemical composition verified. The method is applied to line emission measured by SERTS 89 for an active region of the solar corona and use is made of the Arcetri spectral code and the CHIANTI atomic data base to evaluate the theoretical expected intensities. Lines of He II, C IV, Ne V and VI, Mg VI,VII,VIII and IX, Si VIII,IX,X and XI, S XIII and XIV, Cr XIII and XIV, Fe X,XI,XII,XIII XIV,XV,XVI and XVII and Ni XVIII are used to put constraints on the model of the density versus temperature and on the Differential Emission Measure, and suggestions are given on how to use the method to verify intensity calibrations and identify lines for which atomic physics must be improved.