In the Helios 2 perihelion (0.3 AU) im May 1978, pronounced ion differential speeds Δvop>0 and large proton temperature anisotropies T∥p/T⊥p<1 have been observed in slow solar wind, in distinct contrast to earlier observations during the phase of solar activity minimum. These features of ion distributions occurred simultaneously with high Alfv¿nic wave activity. Coulomb friction between the two ion species can be shown to play a minor role, thus obviously favouring the establishment of a large differential ion speed by preferentially accelerating wave forces. The observations may also indicate that strong waves sometimes only heat the protons without creating a fast solar wind.