Wakefield Acceleration by Radiation Pressure in Relativistic Shock Waves

TL;DR

This paper explores how radiation pressure from precursor waves in relativistic shocks can rapidly accelerate particles to high energies via wakefield mechanisms, with implications for astrophysical particle acceleration.

Contribution

It introduces a novel particle acceleration mechanism involving wakefields generated by precursor waves in relativistic shocks, extending understanding of high-energy astrophysical phenomena.

Findings

Electromagnetic precursor waves excite wakefields that accelerate particles.

Particles can reach energies comparable to the shock Lorentz factor.

Maximum energy depends on system size and plasma parameters.

Abstract

A particle acceleration mechanism by radiation pressure of precursor waves in a relativistic shock is studied. For a relativistic, perpendicular shock with the upstream bulk Lorentz factor of $\gamma_1 \gg 1$, large amplitude electromagnetic (light) waves are known to be excited in the shock front due to the synchrotron maser instability, and those waves can propagate towards upstream as precursor waves. We find that non-thermal, high energy electrons and ions can be quickly produced by an action of electrostatic wakefields generated by the ponderomotive force of the precursor waves. The particles can be quickly accelerated up to $\epsilon_{\rm max}/\gamma_1 m_e c^2 \sim \gamma_1$ in the upstream coherent wakefield region, and they can be further accelerated during the nonlinear stage of the wakefield evolution. The maximum attainable energy is estimated by $\epsilon_{\rm max}/\gamma_1 m_e c^2 \sim L_{\rm sys}/(c/\omega_{pe})$, where $L_{\rm sys}$ and $c/\omega_{pe}$ are the size of an astrophysical object and the electron inertial length, respectively.