1. Laboratoire de Physique des Plasmas On the origin of the quasi-perpendicular Ion Foreshock: 2D Full-particle simulation Poster session ST1.3 : XY663 (EGU2012-4124) Philippe Savoini 1, Bertrand Lembège 2 and Joël Stienlet 1 1 LPP/X/UPMC Route de Saclay, 91128 Palaiseau Cédex 2 LATMOS/UVSQ/IPSL, Boulevard D’Alembert, 78280 Guyancourt

2. Experimental data: Evidence of TWO distinct foreshock populations [Paschmann et al., 1981; Gurgiolo et al., 1981; Fuselier et al., 1986, 1995; Eastwood et al., 2005; Kucharek, 2008] An example of local ion distribution: see poster for more examples Velocity space Field-Aligned Beam (FAB) Gyro-Phase Bunched (GPB) [Mazelle et al., 2003] 2D PIC Numerical results: Ion foreshock Pitch Angle No clear separation of FAB and GPB - No ion instabilities - Origin shock front itself - Need refined selection criteria

3. Two criterion selection :  t int and  depth  int : Interaction time with the shock wave D depth : Penetration depth into the shock wave 1) Both FAB and GPB recovered 2) FAB: Important interaction time (1 ≤  ci ≤ 5) ➙ Multi-bounces on shock front 3) GPB: Short interaction time ( ≤ 1  ci ) ➙ Suffer only One bounce ➙ Can be produced by El ➙ No instabilities needed to produce Non Gyrotropic populations