Microscopic Processes in Global Relativistic Jets Containing Helical Magnetic Fields: Dependence on Jet Radius

TL;DR

This study explores how the size of relativistic jets with helical magnetic fields influences microscopic kinetic instabilities and jet evolution, revealing size-dependent behaviors and new instability phenomena.

Contribution

It provides the first large-scale simulation analysis of global relativistic jets with helical magnetic fields, highlighting the impact of jet radius on instability development.

Findings

Jet evolution depends strongly on jet radius.

Larger jets exhibit more complex magnetic structures and instabilities.

New types of instabilities emerge in global jet simulations.

Abstract

In this study we investigate jet interaction at a microscopic level in a cosmological environment, which responds to a key open question in the study of relativistic jets. Using small simulation systems during prior research, we initially studied the evolution of both electron-proton and electron-positron relativistic jets containing helical magnetic fields, by focusing on their interactions with an ambient plasma. Here, using larger jet radii, we have performed simulations of global jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the Mushroom instability (MI). We found that the evolution of global jets strongly depends on the size of the jet radius. For example, phase bunching of jet electrons, in particular in the electron-proton jet, is mixed with larger jet radius due to the more complicated structures of magnetic fields with excited kinetic instabilities. In our simulation study these kinetic instabilities lead to new types of instabilities in global jets. In the electron-proton jet simulation a modified recollimation occurs and jet electrons are strongly perturbed. In the electron-positron jet simulation mixed kinetic instabilities occur at early times followed by a turbulence-like structure. Simulations using much larger (and longer) systems are further required in order to thoroughly investigate the evolution of global jets containing helical magnetic fields.