English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

High resolution Very Long Baseline Interferometry (VLBI) observations ofActive Galactic Nuclei (AGN) revealed traveling and stationary orquasi-stationary radio-components in several blazar jets. The traveling onesare in general interpreted as shock waves generated by pressure perturbationsinjected at the jet nozzle. The stationary features can be interpreted asrecollimation shocks in non-pressure matched jets if they show aquasi-symmetric bump in the spectral index distribution. In some jets there maybe interactions between the two kinds of shocks. These shock--shockinteractions are observable with VLBI techniques, and their signature shouldalso be imprinted on the single--dish light curves. We performed relativistichydrodynamic (RHD) simulations of over-pressured and pressure-matched jets. Tosimulate the shock interaction we injected a perturbation at the jet nozzleonce a steady-state was reached. We computed the non-thermal emission(including adiabatic and synchotron losses) resulting from the simulation. Weshow that the injection of perturbations in a jet can produce a bump inemission at GHz frequencies previous to the main flare, which is produced whenthe perturbation fills the jet in the observer's frame. The detailed analysisof our simulations and the non-thermal emission calculations show thatinteraction between a recollimation shock and traveling shock produce a typicaland clear signature in both the single--dish light curves and in the VLBIobservations: the flaring peaks are higher and delayed with respect to theevolution of a perturbation through a conical jet. This fact can allow todetect such interactions for stationary components lying outside of the regionin where the losses are dominated by inverse Compton scattering.

Spectral evolution of flaring blazars from numerical simulations