This comment provides the correct expression for the Alfv¿n wave force/unit volume acting on an ion species flowing along the background magnetic field direction. In very sub-Alfv¿nic flow the exact expression is well approximated by the one used by Leer et al. (1992), and it therefore provides an adequate description of the action of Alfv¿n wave forces in the initial acceleration of the wind. It is pointed out that the ''regulation effect'' can be interpreted within the concept of one generalized ''sonic points'' of the coupled bi-ion flow equations. ¿ American Geophysical Union 1994