Dynamics of Relativistic Shock Waves Subject to a Strong Radiation Drag: Similarity Solutions and Numerical Simulations

TL;DR

This study investigates how strong radiation drag influences the behavior of relativistic shock waves, revealing significant effects on shock structure and potential impacts on observed emissions during blazar flares.

Contribution

It provides new similarity solutions and numerical simulations demonstrating the impact of Compton radiation drag on relativistic shock dynamics.

Findings

Radiation drag significantly alters shock structure and evolution.

Reverse shock is strengthened, forward shock is weakened over cooling timescales.

Implications for light curves and spectra during blazar flares.

Abstract

We examine the effect of Compton drag on the dynamics of a relativistic shock wave. Similarity solutions describing a radiation-supported shock are obtained for certain profiles of the external radiation intensity and the density of the unshocked ejecta, and are compared with 1D numerical simulations of a blast wave expanding into an ambient medium containing isotropic seed radiation. Both the analytic model and the simulations indicate that under realistic conditions the radiation drag should strongly affect the dynamics and structure of the shocked layer. In particular, our calculations show significant strengthening of the reverse shock and weakening of the forward shock over time of the order of the inverse Compton cooling time. We conclude that the effect of radiation drag on the evolution of the emitting plasma should affect the resultant light curves and, conceivably, spectra of the observed emission during strong blazar flares.