The internal structure of overpressured, magnetized, relativistic jets

TL;DR

This study characterizes the internal structure of overpressured, relativistic jets with various energy dominances using magnetohydrodynamic simulations, revealing how energy type influences jet features and stability.

Contribution

First detailed analysis linking jet internal structure to energy dominance and magnetization through comprehensive MHD simulations.

Findings

Hot jets exhibit recollimation shocks and large Lorentz factor variations.

Kinetically dominated jets are featureless with small Lorentz factor changes.

High magnetization jets are susceptible to magnetic pinch instabilities.

Abstract

This work presents the first characterization of the internal structure of overpressured steady superfast magnetosonic relativistic jets in connection with their dominant type of energy. To this aim, relativistic magnetohydrodynamic simulations of different jet models threaded by a helical magnetic field have been analyzed covering a wide region in the magnetosonic Mach number - specific internal energy plane. The merit of this plane is that models dominated by different types of energy (internal energy: hot jets; rest-mass energy: kinetically dominated jets; magnetic energy: Poynting-flux dominated jets) occupy well separated regions. The analyzed models also cover a wide range of magnetizations. Models dominated by the internal energy (i.e., hot models, or Poynting-flux dominated jets with magnetizations larger than but close to 1) have a rich internal structure characterized by a series of recollimation shocks and present the largest variations in the flow Lorentz factor (and internal energy density). Conversely, in kinetically dominated models there is not much internal nor magnetic energy to be converted into kinetic one and the jets are featureless, with small variations in the flow Lorentz factor. The presence of a significant toroidal magnetic field threading the jet produces large gradients in the transversal profile of the internal energy density. Poynting-flux dominated models with high magnetization (>10) are prone to be unstable against magnetic pinch modes, which sets limits to the expected magnetization in parsec-scale AGN jets {and/or constrains their magnetic field configuration}.