2019/09/13 by Rostom Mbarek, Mbarek, Rostom, Damiano Caprioli +1 · 2 citations
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #Neutrino Physics Research
paper · pdf · doi:10.48550/arxiv.1909.06390
openalex publication_date 2019/09/13 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Espresso is a novel acceleration model for Ultra-High-Energy Cosmic Rays\n(UHECRs), where lower-energy CRs produced in supernova remnants experience a\none-shot reacceleration in the relativistic jets of powerful Active Galactic\nNuclei (AGNs) to reach energies up to 1020 eV. To test the espresso\nframework, we follow UHECR acceleration bottom-up from injection to the highest\nenergies by propagating 100,000 particles in realistic 3D magneto-hydrodynamic\n(MHD) simulations of ultra-relativistic jets. We find that simulations agree\nwell with analytical expectations in terms of trajectories of individual\nparticles. We also quantify that \∼ 10 % of CR seeds gain a factor of\n\∼\Γ2 in energy, where \Γ is the jet's effective Lorentz factor;\nmoreover, about 0.1 % of the particles undergo two or more shots to achieve\ngains in excess of \Γ2. Particles are generally accelerated up to the\njet's Hillas limit, indicating that the espresso mechanism should boost\ngalactic CRs to UHECRs in typical AGN jets. Finally, we discuss how espresso\nacceleration in AGN jets is consistent with UHECR spectra and chemical\ncomposition, and also with the UHECR arrival directions measured by Auger and\nTelescope Array.\n