Particle Acceleration, Magnetic Field Generation, and Associated Emission in Collisionless Relativistic Jets

TL;DR

This paper discusses how plasma instabilities in collisionless relativistic jets generate magnetic fields and accelerate particles, leading to jitter radiation that could explain observed emissions in astrophysical phenomena like GRBs and AGNs.

Contribution

It presents PIC simulation results showing the role of Weibel instability in magnetic field generation and particle acceleration in relativistic jets, highlighting jitter radiation as a key emission mechanism.

Findings

Weibel instability amplifies small-scale magnetic fields in shocks.

Particle acceleration occurs within the downstream jet region.

Jitter radiation differs from traditional synchrotron emission, affecting spectral interpretations.

Abstract

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks 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 has different properties than synchrotron radiation which assumes a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants.