Radiation from relativistic jets

TL;DR

This paper reviews how relativistic jets produce nonthermal radiation through instabilities like the Weibel instability, which generate small-scale magnetic fields leading to jitter radiation, relevant for understanding gamma-ray bursts and other astrophysical phenomena.

Contribution

It highlights the role of plasma instabilities in jet shock formation and introduces jitter radiation as a distinct emission mechanism from traditional synchrotron radiation.

Findings

Weibel instability generates small-scale magnetic fields in relativistic jets.

Jitter radiation differs from synchrotron radiation in spectral properties.

Simulations show particle acceleration occurs within downstream jets.

Abstract

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., gamma-ray bursts (GRBs), active galactic nuclei (AGNs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations of relativistic electron-ion (electron-positron) jets injected into a stationary medium show that particle acceleration occurs within the downstream jet. In the presence of relativistic jets, instabilities such as the Buneman instability, other two-streaming instability, and the Weibel (filamentation) instability create collisionless shocks, which are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The ``jitter'' radiation from deflected electrons in small-scale magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation, a case of diffusive synchrotron radiation, may be important to understand the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.