Preferential Positron Acceleration in Relativistic Magnetized Electron–Positron–Ion Shocks

Abstract Relativistic shocks are considered efficient accelerators of charged particles and play crucial roles in high-energy astrophysical phenomena, such as gamma-ray bursts and pulsar winds. This study focuses on positron accelerations in magnetized relativistic shocks in electron–positron–ion plasma. Employing 1D ab initio particle-in-cell simulations, we found a preferential positron acceleration through an interaction with the wakefield associated with a precursor wave in the upstream region. Test particle simulations revealed that the selective acceleration occurs for sufficiently large amplitudes of the wakefield. The mechanism can be understood as the relativistic E × B acceleration formulated in the upstream frame. A theoretical analysis of the positron acceleration in astrophysical contexts is presented, supporting ultrarelativistic shocks in pulsar winds as a primary source for the high-energy positron excess.