  We analyze time series data of the fluctuations of slow solar wind velocity
using rank order statistics. We selected a total of 18 datasets measured by the
Helios spacecraft at a distance of 0.32 AU from the sun in the inner
heliosphere. The datasets correspond to the years 1975-1982 and cover the end
of the solar activity cycle 20 to the middle of the activity cycle 21. We first
apply rank order statistics to time series from known nonlinear systems and
then extend the analysis to the solar wind data. We find that the underlying
dynamics governing the solar wind velocity remains almost unchanged during an
activity cycle. However, during a solar activity cycle the fluctuations in the
slow solar wind time series increase just before the maximum of the activity
cycle
