  We study the height variations of the sizes of chromospheric and
transition-region features in a small coronal hole and the adjacent quiet Sun,
considering images of the intensity, Doppler shift, and non-thermal motion of
ultraviolet emission lines as measured by SUMER, together with the magnetic
field as obtained by extrapolation from photospheric magnetograms. In order to
estimate the characteristic sizes of the different features present in the
chromosphere and transition region, we have calculated the autocorrelation
function for the images as well as the corresponding extrapolated magnetic
field at different heights. The HWHM of the autocorrelation function is
considered to be the characteristic size of the feature shown in the
corresponding image. Our results indicate that, in both the coronal hole and
quiet Sun, the HWHM of the intensity image is larger than that of the images of
Doppler-shift and non-thermal width at any given altitude. The HWHM of the
intensity image is smaller in the chromosphere than in the TR, where the sizes
of intensity features of lines at different temperatures are almost the same.
But in the upper part of the transition region, the intensity size increases
more strongly with temperature in the coronal hole than in the quiet Sun. We
also studied the height variations of the HWHM of the magnetic field magnitude
B and its component |Bz|, and found they are equal to each other at a certain
height below 40 Mm in the coronal hole. The height variations of the HWHM of
|Bz/B| seem to be consistent with the temperature variations of the intensity
size. Our results suggest that coronal loops are much lower, and magnetic
structures expand through the upper TR and lower corona much more strongly with
height in the coronal hole than in the quiet Sun.
