[en] Wave-particle interactions in nonlinear magnetosonic waves are studied with a one-dimensional (one spatial coordinate and three velocity components), fully relativistic particle simulation code with full ion and electron dynamics. Particular attention is given to the acceleration of energetic ions whose initial speeds are comparable to or greater than the Alfven speed. Simulations show that some of the energetic ions call be accelerated by the transverse electric field in a magnetosonic wave. The change in energy increases with increasing initial particle energy. The present results suggest that, if particles encounter with magnetosonic pulses many times, then high-energy ions with speeds much greater than the Alfven speed could be produced. (author)