  Spectroscopic studies of the solar corona, using the high spatial and
spectral resolution 25-cm coronagraph at the Norikura observatory for
equatorial off-limb observations, indicated that the variation of radiance and
line width with height is different for different temperature lines. The line
width of the forbidden red emission line [\FeX] 6374 \AA was found to increase
with height and that of the green emission line [\FeXIV] 5303 \AA decrease with
height. This had been interpreted in terms of the interaction between different
temperature plasma but needed to be confirmed. Further observations were made
on several days during 2004, in two emission lines simultaneously covering the
mid-latitude and polar regions to investigate the existence of the observed
variation in other parts of the solar corona. In this study, we have analysed
several raster scans that cover mid- and high-latitude regions of the off-limb
corona in all four bright emission lines [\FeX] 6374 \AA, [\FeXI] 7892 \AA,
[\FeXIII] 10747 \AA, and [\FeXIV] 5303 \AA. We find that the FWHM of the red
line increases with height and that of the green line decreases with height
similar to that observed in equatorial regions. The line widths are found to be
higher in polar regions for all of the observed emission lines except for the
green line. Higher values of FWHM in polar regions may imply higher non-thermal
velocities which could be further linked to a non-thermal source powering the
solar-wind acceleration, but the reason for the behaviour of the green emission
line remains to be explored.
