Recent calculations and computer simulations of the right‐hand resonant ion beam instability have indicated that gyrophase‐bunched ion distributions may be generated as a first step in the disruption of field‐aligned beams. Theory predicts a distinct phase angle relationship between the gyrovelocity of the phase‐bunched ions and the wave magnetic field. In this paper, observations of such a relationship between gyrophase‐bunched ions and MHD‐like waves upstream from the Earth's bow shock are presented. The observed phases are in accord with the theoretical predictions of the right‐hand resonant ion bea