Particle flux variations associated with low-frequency hydromagnetic waves have been examined by using Ogo 5 data obtained with the Lockheed ion mass spectrometer, the Lawrence Livermore Laboratory electron and proton spectro-meters, the University of California at Los Angeles (UCLA) energetic electron spectrometers, and the UCLA flux gate magnetometer. It was found that quasi-periodic perturbations in the thermal ion (E?600 eV), energetic electron (E?50 keV), and proton (E?100 keV) fluxes were usually associated with the occurrence of Pc 5 waves in the region of L=6-11. Amplitudes of perturbations in the ion density, inferred from the assumption that the ambient cold plasma was at rest, often reached 10--50 ions/cm3. The ion density variations were usually found to be either 90¿ or 270¿ out of phase with the magnetic perturbations. It is concluded that these large apparent perturbations of ion density are attributable of drift velocity variations of the ambient plasma induced by hydromagnetic waves. From the phase differences between the thermal particle flux and the magnetic field variations it is argued that the time-averaged Poynting flux of Pc 5 waves along the ambient magnetic field is approximately zero; this indicates that Pc 5 waves are standing waves along the field line. Flux modulations of the energetic electrons and protons are more complicated than those of the thermal ions. The relative phase of the variations is often found to depend on the energy of the particles. We have found that the proton modulations are usually larger in the morning than in the afternoon, while electron modulations dominate in the afternoon. This fact is consistent with an azimuthal phase velocity of the Pc 5 waves directed from noon to midnight in both the morning and the afternoon and indicates that drift motions of energetic particles can interact strongly with the oscillations of field lines; these observations are consistent with the energy source of the Pc 5 oscillations originating mainly from the Kelvin-Helmholtz instability at the magnetopause as suggested in recent theories.