Elemental abundances of the low corona as derived from SOHO/CDS observations

Some of the main factors that affect the determination of the element abundances from EUV spectra are reviewed. The ionization balance, the selection of lines, and the spectroscopic method used can each account for a variation of a factor of two or more in the derived element abundances, in particular cases. Diagnostic techniques are applied to Skylab/HCO and SOHO/CDS observations of solar coronal holes and plumes, in order to derive their relative element abundances. It is confirmed that coronal holes have photospheric abundances, while plumes only show a small FIP effect, contrary to what has long been thought. It is shown that the plume characteristics can mainly be explained in terms of their temperature structure rather than a large FIP effect.