Recollimation Shocks in Magnetized Relativistic Jets

Abstract

We have performed two-dimensional special-relativistic magnetohydrodynamic simulations of nonequilibrium over-pressured relativistic jets in cylindrical geometry. Multiple stationary recollimation shock and rarefaction structures are produced along the jet by the nonlinear interaction of shocks and rarefaction waves excited at the interface between the jet and the surrounding ambient medium. Although initially the jet is kinematically dominated, we have considered axial, toroidal and helical magnetic fields to investigate the effects of different magnetic-field topologies and strengths on the recollimation structures. We find that an axial field introduces a larger effective gas-pressure and leads to stronger recollimation shocks and rarefactions, resulting in larger flow variations. The jet boost grows quadratically with the initial magnetic field. On the other hand, a toroidal field leads to weaker recollimation shocks and rarefactions, modifying significantly the jet structure after the first recollimation rarefaction and shock. The jet boost decreases systematically. For a helical field, instead, the behaviour depends on the magnetic pitch, with a phenomenology that ranges between the one seen for axial and toroidal magnetic fields, respectively. In general, however, a helical magnetic field yields a more complex shock and rarefaction substructure close to the inlet that significantly modifies the jet structure. The differences in shock structure resulting from different field configurations and strengths may have observable consequences for disturbances propagating through a stationary recollimation shock.

Radiative Signatures of Parsec-Scale Magnetised Jets

“…As a result, magnetised jets are more collimated and show a shorter wavelength in the oscillation of the jet boundary as compared to less magnetised jets. In addition, the increase of the magnetisation induces a higher magnetic tension and the formation of recollimation shocks is suppressed (e.g., [11,16]). …”

PROBING THE INNERMOST REGIONS OF AGN JETS AND THEIR MAGNETIC FIELDS WITH RADIOASTRON. I. IMAGING BL LACERTAE AT 21 μas RESOLUTION

“…The initial set-up follows Gómez et al (1997) and Mizuno et al (2015), in which a preexisting over-pressured flow is established across the simulation domain. We choose a restmass density ratio between the jet and ambient medium of r (e.g., Gómez et al 1995Gómez et al , 1997Mimica et al 2009).…”

High-Precision Astrometric Millimeter Very Long Baseline Interferometry Using a New Method for Multi-Frequency Calibration

“…A burst in particle and magnetic energy density is therefore required when jet disturbances cross the radio core in order to produce γ-ray flares, which can naturally be explained by identifying the radio core with a recollimation shock (e.g., Daly & Marscher 1988;Gómez et al 1995Gómez et al , 1997Marscher 2009Marscher , 2012Mizuno et al 2015;Martí et al 2016). …”