The widths of vacuum-ultraviolet spectral lines in the equatorial solar corona observed with CDS and SUMER

Abstract

Observations of the solar equatorial corona between heights of 36 Mm and 184 Mm above the limb obtained by the SOHO spectrometers CDS and SUMER in December 2003 are presented and discussed with special emphasis on the widths of the spectral lines Mg X at 62.50 nm, Al XI at 55.00 nm and 56.82 nm, Ca X at 55.78 nm, and Si XI at 58.09 nm. SUMER observed, in addition, the lines Mg X 60.98 nm, Ca X 57.40 nm, Fe XII 124.20 nm, Fe XVII 115.31 nm, and Ca XIII 113.37 nm. The Si XII 52.11 nm line was only observed by CDS. A different behaviour of the line width of Mg X 62.50 nm as a function of height above the limb had been found in studies carried out independently with both instruments at different times. It is the aim of this joint investigation to (a) study instrumental effects on line-width results; and (b) provide a thorough analysis of line profiles with altitude for the new campaign. © ESO 2005.