We report on measurements of energetic particle modulations (ions and electrons with energies E>50 keV) observed by the heliosphere instrument for spectra, composition, and anisotropy at low energies (HI-SCALE) aboard the Ulysses spacecraft that were associated with the only hydromagnetic (HM) wave event measured inside the Jovian magnetosphere by the Ulysses magnetometer investigation. This HM-wave event occurred during the high latitude outbound pass of the spacecraft in the dusk sector of the planet at distances between 65 and 68 Jovian radii (RJ) and at southern magnetic latitudes between 27¿ and 32¿. We show that the approximately 5-min oscillations that occurred for about an hour in the north-south component of the magnetic field are well correlated with variations of the energetic particle fluxes at small pitch angles. The detection of the narrow angle ion beams by the HI-SCALE instrument occurs at the intersection between two angular spin sectors. The small-amplitude waves vary the magnetic field direction sufficiently that the beam is directed primarily toward one sector and then the other, and back again. Possible mechanisms for the HM-wave generation are explained. We show that the HM waves are most likely to be generated by the presence of magnetospheric heavy ions (i.e., sulfur or oxygen) with energies in the range of a few keV. ¿ American Geophysical Union 1996