On the angular anisotropy of the distribution function of radiating particles in relativistic jets

TL;DR

This paper investigates how the angular distribution of radiating particles in relativistic jets evolves, revealing that electric fields and drift motion prevent pitch angle decrease, impacting jet emission models.

Contribution

It introduces a study of angular anisotropy evolution of particles in relativistic jets considering electric fields and drift motion effects.

Findings

Electric fields prevent pitch angle decrease in relativistic jets.

Drift motion influences particle angular distribution.

Angular anisotropy affects jet radiation characteristics.

Abstract

The observed power-law spectra of relativistic jets from active galactic nuclei clearly indicate a synchrotron mechanism of radiation by particles that similarly possess a power-law energy spectrum. However, the issue of their angular anisotropy has not been given sufficient attention until recently, although the example of the solar wind (where a strongly magnetized wind is realized in a similar way) shows the importance of taking this circumstance into account. In this paper, we study the evolution of an initially isotropic power-law spectrum of radiating particles as they propagate along expanding relativistic jets. It is shown that for relativistic flows in which the electric field plays a crucial role, the preservation of the first adiabatic invariant does not lead to a decrease in the pitch angles of radiating particles as they enter the region of weak magnetic fields. This is due to the drift nature of the particle motion.