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On the maximum energy of particles accelerated in astrophysical jets

Project description

Mathematical models help us get a handle on a cosmic form of "jet propulsion"

Much as an explosion here on Earth produces shocks that accelerate nearby objects, shock waves from cosmic phenomena in our universe can accelerate space particles. Astrophysical jets, beams of matter ejected from certain astronomical objects including active galactic nuclei, are known to produce such shocks. However, we are not clear about the maximum energy space particles can reach because of their acceleration, and this is fundamental to the identification and understanding of high-energy particles in our galaxy. The EU-funded EMAXSHOCK project is investigating this open question via pioneering computational models.


Astrophysical jets moving in an external medium produce shocks where particles can be accelerated via Diffusive Shock Acceleration (DSA). The main uncertainty is the maximum energy that particles can achieve, and this has important implications for different fields in astrophysics. In particular, one of the most exciting problems is the origin of the Ultra High Energy Cosmic Rays, and jets from Active Galactic Nuclei (AGN) have been proposed as candidates. At lower energies cosmic rays are likely galactic. With that respect, a large fraction of gamma-ray
sources in the Galaxy remain unidentified, and protostellar jets are among candidates to be the hidden cosmic ray accelerators. It was very recently demonstrated that mildly relativistic shocks in the backflows in the lobes of AGN jets can accelerate particles up to the Hillas energy,
offering a suitable environment for the acceleration of UHECRs. However, in order to account for the heavy composition of the UHECR spectrum, a jet mass loading mechanism is needed. At lower energies, acceleration of TeV particles in protostellar jets can be quenched by ion-neutral collisions, and therefore kinetic calculations are desirable in order to
compute the maximum energy of particles in low velocity shocks and non-completely ionized plasmas.
I will investigate the maximum energy that particles can achieve when they are accelerated via DSA in mildly-relativistic and low-velocity shocks, in AGN and protostellar jets, respectively. In the former case I will consider the shocks produced by the interaction of powerful stellar winds with the jets, whereas in the latter case we will consider the jet termination shocks. By performing unprecedented calculations with the a newly developed hybrid code, I aim to address the maximum energy and composition of the UHECR spectrum by modeling the backflows of jet/wind interactions. In addition, I aim to address if protostellar jets can accelerate TeV particles and emit gamma rays.


Net EU contribution
€ 184 707,84
75794 Paris

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Ile-de-France Ile-de-France Paris
Activity type
Research Organisations
Total cost
€ 184 707,84