Coherent Electromagnetic Emission from Relativistic Magnetized Shocks

Relativistic magnetized shocks are a natural source of coherent emission, offering a plausible radiative mechanism for fast radio bursts (FRBs). We present first-principles 3D simulations that provide essential information for the FRB models based on shocks: the emission efficiency, spectrum, and polarization. The simulated shock propagates in an e^± plasma with magnetization σ >1 . The measured fraction of shock energy converted to coherent radiation is ≃10^-3σ^-1, and the energy-carrying wave number of the wave spectrum is ≃4 ω_c/c , where ω_c is the upstream gyrofrequency. The ratio of the O -mode and X -mode energy fluxes emitted by the shock is ≃0.4 σ^-1. The dominance of the X mode at σ ≫1 is particularly strong, approaching 100% in the spectral band around 2 ω_c. We also provide a detailed description of the emission mechanism for both X and O modes.