Quasi-Stationary and Transient Patterns in Jets

TL;DR

This paper reviews how complex interactions of plasma dynamics, instabilities, and relativistic effects create diverse observable patterns in astrophysical jets, affecting their analysis and interpretation.

Contribution

It provides a comprehensive review of the formation and nature of stationary and transient patterns in jets, linking them to plasma instabilities, shocks, and relativistic effects.

Findings

Quasi-stationary patterns are likely caused by plasma instabilities.

Fast-moving patterns are associated with relativistic plasma condensations.

Stationary features may be related to recollimation shocks or non-thermal emission regions.

Abstract

Apparent evolution of relativistic flows as traced by radio emission results from a combination of several factors related to propagation of relativistic blobs or shocks, velocity, density and pressure stratification of the underlying flow, plasma instability and (possibly also) phase and time travel effect. This combination can create an intricate and chaotic patterns of the observed morphological changes in radio emission, which complicates the analysis and interpretation of kinematic and physical properties of the jet plasma. Recent studies have indicated that slow and quasi-stationary patterns in jets are most likely formed by plasma instabilities while faster, superluminally moving patterns are related to highly relativistic plasma condensations produced by the nuclear flares. Some of the stationary patterns may also be related to recollimation shocks or locations where strong non-thermal continuum is produced in jets. Similarities and differences of the AGN and XRB jets in this respect are reviewed.