Characterization of solar coronal holes and plumes using spectroscopic diagnostic techniques applied to SOHO/CDS observations

Results from a series of SOHO/Coronal Diagnostic Spectrometer (CDS) observa tions of coronal holes and plumes are presented, including analysis of a lo w-latitude plume observed in August 1996. Spectroscopic diagnostic techniqu es using the CHIANTI atomic database are applied to derive the plasma param eters: electron density, temperature, and element abundances. The results a re compared with quiet sun values. Coronal electron densities in the holes are found to be about 2 x 10(8) cm, a factor of two to three lower than in the quiet sun. The plasma thermal distribution exhibits differences between coronal holes, the quiet sun and plumes. For example, the peak of the emis sion in coronal holes is at a lower temperature (T similar or equal to 8 x 10(5) K) than in the quiet sun (T similar or equal to 1 x 10(6) K), while p lumes are cooler (T similar or equal to 7.6 x 10(5) K) and show a different distribution, closer to an isothermal state.