Comparison between self-consistent 2D full-particle and test-particles simulations to investigate the origin of the Earth's Ion Foreshock.

Backstreaming ion populations propagating along the interplanetary magnetic field are evidenced upstream of the Terrestrial curved bow shock and form the ion foreshock. Two distinct backstreaming populations have been identified by spacecrafts within the quasi-perpendicular shock region (i.e. for45o ≤θBn ≤90o, where θBn is the angle between the shock normal and the upstream magnetostatic field): so called (i) field-aligned ion beams (« FAB») characterized by a gyrotropic distribution, and (ii) gyro-phase bunched ions («GPB »), characterized by a NON gyrotropic distribution. The origin of these backstreaming ions can be analyzed within an « enlarged » upstream region near/around the front with the help of 2D PIC simulation of a curved shock, where full curvature effects, time of flight effects and both electrons and ions dynamics are fully included by a self consistent approach. ...