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An extensive analysis of Ulysses observations of the solar wind speed V from1990 to 2008 is undertaken. It is shown that the evolution of V withheliocentric distance r depends substantially on both the heliolatitude and thesolar activity cycle. Deviations from the predicted Parker's profile of V(r)are so considerable that cannot be explained by a scarcity of measurements orother technical effects. In particular, the expected smooth growth of the solarwind speed with r is typical only for the solar activity maximum and for lowheliolatitudes (lower than +/-40deg), while at high latitudes, there are twoV(r) branches: growing and falling. In the solar activity maximum, V increasestoward the solar pole in the North hemisphere only; however, in the Southhemisphere, it decreases with heliolatitude. In the minimum of solar activity,the profile of V(r) at low heliolatitudes has a local minimum between 2 and 5AU. This result is confirmed by the corresponding data from other spacecraft(Voyager 1 and Pioneer 10). Unexpected spatial variations in V at lowheliolatitudes can be explained by the impact of coronal hole flows on the V(r)profile since the flows incline to the ecliptic plane. To reproduce the impactof spatial variations of V in the polar corona on the behavior of V at lowheliolatitudes, a stationary one-fluid ideal MHD-model is developed withaccount of recent results on imagery of the solar wind speed in the corona upto 5.5 solar radii obtained on the basis of combined observations fromSOHO/UVCS, LASCO, and Mauna Loa.

plasma physics reports

Evolution of the solar wind speed with heliocentric distance and solar  cycle. Surprises from Ulysses and unexpectedness from observations of the  solar corona