Corolal Evolution during a Solar Cycle with Synoptic Maps from SOHO/UVCS Observations

The UVCS instrument aboard SOHO provides, for the first time, long time series of data for the UV cirina from 1.5 to 3.0 solar radii. The UVCS observationa, performed almost daily from April 1996 to the present day, cover almost the entire solar cycle. Tha data allow the reconstruction of off-limb synoptic maps which represent a powerful tool to obtain information on the short and long termo coronal evolution. In this work we describe the techniques for reconstructing the synoptic maps of the spectral line parameters derived by fitting the UVCS data. We obtain the intensity synoptic maps of the main spectral lines observed by UVCS (H I Ly alpha, O VI doublet and Si XII), the temperature maps of H I atoms and O VI ions, the maps of the O VI doublet ratio and the inferred O/H abundance map at different heliocentric heights.These maps represent the evolution over the solar cycle of the physical properties of the corona (such as densities, temperatures and outflow velocities) and allow the study of the variation of the large scale structures, such as high and low latitude coronal holes and quiescent and active streamers. Moreover they yield a unique opportunuty of validating potential coronal magnetic field models obtained exrapolating photospheric measurements.