Can a strong radio burst escape the magnetosphere of a magnetar?

TL;DR

This paper investigates whether fast radio bursts can escape a magnetar's magnetosphere, finding that interactions with plasma likely prevent their escape unless emitted from larger radii, favoring models with energy transport to greater distances.

Contribution

It demonstrates that FRBs originating within the magnetosphere are unlikely to escape due to scattering and absorption, supporting models where energy is transported to larger radii before emission.

Findings

FRBs strongly interact with magnetospheric plasma, preventing escape at small radii.

Scattering leads to spectrum extension into gamma-ray energies.

Emission at larger radii is more feasible for FRB escape.

Abstract

We examine the possibility that fast radio bursts (FRBs) are emitted inside the magnetosphere of a magnetar. On its way out, the radio wave must interact with a low-density $e^\pm$ plasma in the outer magnetosphere at radii $R=10^9$-$10^{10}\,$cm. In this region, the magnetospheric particles have a huge cross section for scattering the wave. As a result, the wave strongly interacts with the magnetosphere and compresses it, depositing the FRB energy into the compressed field and the scattered radiation. The scattered spectrum extends to the $\gamma$-ray band and triggers $e^\pm$ avalanche, further boosting the opacity. These processes choke FRBs, disfavoring scenarios with a radio source confined at $R\ll 10^{10}\,$cm. Observed FRBs can be emitted by magnetospheric flare ejecta transporting energy to large radii.