Field amplification, vortex formation, and electron acceleration in a plasma protoshock: effect of asymmetric density profile.

Gamma ray bursts (GRBs) are thought to originate from highly relativistic jets. The fireball model predicts internal shocks in the jets, causing magnetic field to be amplified and particles to be accelerated. We model the effects of an asymmetric density configuration for an internal plasma collision in aquasi-parallel magnetic field. We measured electron acceleration and found that a tenuous population of electrons is accelerated to Lorentz factors of ∼ 300- close to energy equipartition with ions. We found that the filaments did not remain static, but were deflected by the Lorentz force and rolled up into smallvortices, which themselves merge to form a larger current vortex.