Upstream Ion Dynamics in Relativistic Collisionless Electron-Ion Shocks

Relativistic collisionless shocks are considered responsible for particle energization mechanisms leading to particle acceleration. We investigate particle energization mechanism in the upstream region of relativistic electron/ion relativistic shocks, using two-dimensional particle-in-cell (PIC) VLPL[1], which is modified to suppress numerical instabilities[1,2]. We discuss mechanism of particle energization which takes place in the upstream region of the shock, where the counter stream particles interact with incoming flow. Tracking a large number of energized ions from the non-thermal tail of the energy spectrum shows that particles in this region are directly accelerated by the large inductive transverse and longitudinal electric fields of the evolving magnetic dipole vortices in this region.

[1] Pukhov, A. J. Plasma Phys. 61, 425. (1999).

[2] N. Naseri, S. Bochkarev, V. Bychenkov, V. Khudik, G. Shvtes, Scientific Reports, 12, 7327 (2022).