Evidence of ion foreshock in 2-D PIC simulations of a curved collisionless shock: Statistical and individual trajectory approach

2-D Full particle simulations are used to investigate the so-called foreshock region which is filled with energized backstreaming particles. Two populations are observed for 90° ≥ Θ_Bn ≥ 45°: (i) field-aligned ion beams collimated along the IMF and having a gyrotropic distribution and (ii) gyro-phase bunch ions having a global gyration around the magnetic field. Our analysis evidences that these two populations are reflected by the shock itself and can have different origins both in term of interaction time, drift along the shock front and distance of penetration ("leaked" ions are observed).