  Quasi-continuous observations of PSR B03239+54 over 20 days using the Nanshan
25-m telescope at 1540 MHz have been used to study the effects of refractive
scintillation on the pulsar flux density and diffractive scintillation
properties. Dynamic spectra were obtained from datasets of 90 min duration and
diffractive parameters derived from a two-dimensional auto-correlation
analysis. Secondary spectra were also computed but these showed no significant
evidence for arc structure. Cross correlations between variations in the
derived parameters were much lower than predicted by thin screen models and in
one case was of opposite sign to the prediction. Observed modulation indices
were larger than predicted by thin screen models with a Kolmogorov fluctuation
spectrum. Structure functions were computed for the flux density, diffractive
timescale and decorrelation bandwidth. These indicated a refractive timescale
of $8\pm 2$ h, much shorter than predicted by the thin screen model. The
measured structure-function slope of $0.4\pm 0.2$ is also inconsistent with
scattering by a single thin screen for which a slope of 2.0 is expected. All
observations are consistent with scattering by an extended medium having a
Kolmogorov fluctuation spectrum which is concentrated towards the pulsar. This
interpretation is also consistent with recent observations of multiple diffuse
scintillation arcs for this pulsar.
