# Rayleigh-Taylor Instability in Two-Component Relativistic Jets

## TL;DR

This study uses 2D simulations to show that pressure-confined two-component relativistic jets develop Rayleigh-Taylor instabilities, leading to internal dissipation and mixing, which may explain observed jet flaring in active galactic nuclei.

## Contribution

It demonstrates that pressure-driven oscillations in two-component relativistic jets induce Rayleigh-Taylor instabilities, contributing to internal dissipation and jet structure complexity.

## Key findings

- Jet oscillations trigger Rayleigh-Taylor instabilities.
- Instabilities cause internal dissipation and mixing.
- Results are consistent across different jet configurations.

## Abstract

Relativistic jets associated with active galactic nuclei and gamma-ray bursts propagate over huge distances without significant loss of momentum. At the same time they are bright emitters, which is indicative of strong energy dissipation. This points towards a mechanism of internal dissipation which does not result in a global disruption of the flow. One possibility is internal shocks and another one is turbulence driven by local instabilities. Such instabilities can be triggered when a freely expanding jet is reconfined by either the cocoon or external gas pressure. In this paper we study the dynamics of two-component spine-sheath hydrodynamic jets coming into pressure equilibrium with external gas using 2D computer simulations. We find that the jet oscillations lead to a rapid onset of Rayleigh-Taylor-type instabilities, which results in additional internal dissipation and mixing of the jet components. Although slightly different in details, this outcome holds both for the heavy-spine-light-sheath and light-spine-heavy-sheath configurations. The results may provide an explanation to the spatial flaring observed in some AGN jets on kpc-scales.