One of the most surprising initial results from UVCS/SOHO was the
extremely broad profile of O VI (oxygen 5+) ions measured high in the
polar coronal holes.

This image shows UVCS/SOHO observations of the O VI 1032 and 1037
Angstrom line profiles at 2.1 solar radii, in a polar coronal hole
(lower panel) (Kohl et al. 1997, Solar Physics, 175, 613). Each
spectral line consists of the coronal profile and a narrow
contribution from a combination of stray light and the F corona.
The data points are shown as crosses, coronal profile components
from curve fits by dashes, and the best fit to the total observed
profile by a solid line.

The widths of the coronal emission lines tell us about the ion
velocity distribution measured along the line of sight. These
extremely broad O VI lines yield velocities up to 500 km/s, which
corresponds to kinetic temperatures of more than 200 million K.

For comparison we show the SUMER/SOHO solar disk observations in the
same range of the spectrum (upper panel). The respective O VI 1032 and
1037 lines are much narrower, with widths of about 30 km/s. The
stray light and F corona component seen in the UVCS/SOHO observations
corresponds to the instrument-scattered solar-disk profile. Thus, it
has the width of the O VI lines observed by SUMER/SOHO.

(The first UVCS results are presented by Kohl et al. 1997,
Solar Physics, 175, 613; the SUMER disk profiles are presented by
Warren et al. 1997, Astrophys. J., 484, L91)