The Effect of Proton Cyclotron Waves on Ion Velocity Distribution at Mars

Proton cyclotron waves (PCWs) have been observed near Mars for a long time. Many statistical studies of the wave characteristics have been reported. However, due to the limited energy and angular resolution of the particle instruments, how the waves interact with ions has not been made clear yet. We develope an improved algorithm to construct the velocity space, which is able to present data as it is originally detected without distortion. Using this algorithm, we report the effect of PCWs on ion, which is the clustering of resonant ions near the orientation of fluctuating magnetic field in velocity space through nonlinear wave-particle interaction, named gyro-phase bunching. We also show the interpretation of such a gyro-phase bunching phenomenon which is given by previous theoretical works.