We discuss the ponderomotive redistribution of ions along geomagnetic field lines due to the action of Pc 1 pulsations, using a simple diffusion equilibrium model. The field-aligned component of the ponderomotive force is derived for Alfv¿n waves as well as for ion cyclotron waves propagating in a multicomponent plasma. Our theory gives a possibility for a better understanding of the problem and a convenient way to make rough estimates of the ponderomotive efficiency of Pc 1 waves under concrete magnetospheric conditions. Qualitative analysis of equations and satellite information on the intensity of wave fields show that the ponderomotive forces can have a pronounced effect on plasma. Ground-based observations of Pc 1 pulsations also suggest a ponderomotive redistribution of the background plasma. ¿ American Geophysical Union 1996