We conducted an analysis of the radial evolution of the wave phenomena observed in the inner solar system and associated with the high velocity solar wind stream pattern. The combined interplanetary magnetic field observations performed by Helios-1 and Helios-2 spacecraft allow to draw the following conclusions: (a) The compressive contribution to field fluctuations with periods less than 6 hr is observed to increase with the increasing heliocentric distance and the total variance of the field components decreases appreciably faster than r−3. (b) When compared with theoretical models, Helios observations confirm a better agreement with wave modes which saturate at a constant value of the ratio between the wave energy density and the ambient field energy density.