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Session 1 - Chromosphere, Corona, Flares.
Display session, Friday, June 27
Ballroom B, Chair: Charles Kankelborg

[1.09] Observations of the Quiet Sun Corona and Coronal Holes with the Coronal Diagnostic Spectrometer on SOHO

A. Fludra (Rutherford Appleton Laboratory, UK), G. Del Zanna, B. J. I. Bromage (University of Central Lancashire, UK)

Limb observations of the quiet sun corona were made with the Coronal Diagnostic Spectrometer (CDS) on SOHO. A particularly large data set was recorded in August 1996 during the Whole Sun Month campaign. Representative examples of CDS images and spectra are shown and their diagnostic capability is discussed. CDS spectra in the wavelength range 150-780 Å\ taken up to 1.3 solar radii above the East and West limb, provide intensities of many spectral lines as a function of the radial distance. Several density-sensitive line ratios (e.g., Si IX, Fe XII, Fe XIII) are used to estimate an average electron density. The temperature distribution above the limb is inferred using lines from different ionization stages of iron, magnesium and silicon: Fe IX-XVI, Mg IX-X, Si XI-XII. The relevance of these measurements to the study of the structure of the lower corona is discussed. CDS observations of polar coronal holes are also analyzed to obtain estimates of electron density and temperature, and to study the morphology and evolution of coronal hole boundaries.

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