The Ultraviolet Coronagraph Spectrometer (UVCS) on the Solar and Heliospher
ic Observatory (SOHO) has been used to measure spectral line profiles for H
I Ly alpha in the south polar coronal hole at projected heliocentric heigh
ts from 3.5 to 6.0 R. during 1998 January 5-11. Observations from 1.5 to 2.
5 R. were made for comparison. The H I Ly alpha profile is the only one obs
ervable with UVCS above 3.5 Ro in coronal holes. Within this region the out
flowing coronal plasma becomes nearly collisionless and the ionization bala
nce is believed to become frozen.
In this paper, the 1/e half widths of the coronal velocity distributions ar
e provided for the observed heights. The velocity distributions include all
motions contributing to the velocities along the line of sight (LOS). The
observations have been corrected for instrumental effects and interplanetar
y H I Ly alpha. The half widths were found to increase with projected helio
graphic height from 1.5 to 2.5 R. and decrease with height from 3.5 to 5 R.