SPECTROSCOPIC METHODS FOR CORONAL DIAGNOSTICS

The EUV spectre present a rich source of information on the nature of the solar corona and the principal means of understanding the underlying mechanisms. Line shifts and broadening give information about the dynamic phenomena in the solar atmosphere and permit a measurement of heating processes (waves, turbulence...). Well chosen line intensity ratios provide knowledge of either the electron temperature or electron density. Absolute intensities of lines corresponding to a large range of temperature give a differential emission measure for the region being viewed and, combined with other physical information, a solution of the density and temperature gradients in that region. These diagnostics are presented and the validity conditions discussed.