Plasma and magnetic field measurements by Ulysses are used to investigate t
he radial evolution of hourly-scale Alfvenic fluctuations in the polar wind
. The data span from 1.4 to 4.3 AU in heliocentric distance. Different radi
al regimes at different distances emerge. Inside about 2.5 AU the large out
ward traveling fluctuations decrease faster, in terms of energy per unit ma
ss, than the small inward ones. This is in agreement with previous low-lati
tude observations inside 1 AU within the trailing edge of fast streams. As
a result of this different gradient the ratio of inward to outward fluctuat
ion energy rises to about 0.5 near 2.5 AU. Beyond this distance the radial
gradient of the inward fluctuations becomes increasingly steeper, while tha
t of the outward ones does not vary appreciably. A state is quickly reached
where both populations decline at almost the same rate. These results on t
he behavior of outward and inward Alfvenic fluctuations are new and represe
nt a constraint for models of turbulence evolution in steadily expanding fl
ows like the polar wind. Finally, an extrapolation to regions near the Sun
would suggest that Alfvenic fluctuations at hourly scale should not play a
relevant role in solar wind heating and acceleration. Obviously, this last
conclusion may be invalidated by non-WKB effects and by compressive and dis
sipative processess close to the Sun.