Shear Particle Acceleration in Astrophysical Jets

• Applicant: Privatdozent Dr. Frank Rieger
• Subject Area: Astrophysics and Astronomy
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467743996

Where and how are the charged particles seen in the Universe accelerated to their extreme energies? Perhaps one of the most promising sites includes the collimated, relativistic outflows or jets in Active Galactic Nuclei (AGN). The growing realisation that these jets are likely to exhibit significant velocity shearing has in recent times triggered a variety of studies exploring its consequences for non-thermal particle acceleration and emission. Fast shear flows can in principle facilitate energetic particle acceleration by several means. One key possibility includes a stochastic Fermi-type process, in which particle energisation occurs as a result of elastically scattering off differentially moving magnetic inhomogeneities embedded in a shearing background flow.In this project we will address and resolve key issues of Fermi-type shear particle acceleration in the jets of AGN by means of numerical, analytical and phenomenological methods.We specifically aim at (a) a numerical solution of the relativistic particle transport equation for sheared, cylindrical jets, that will enable assessing the adequacy of simplified acceleration models currently used, (b) a numerical verification of the fundamental concept of shear particle acceleration by means of Monte Carlo simulations along with extensions towards anisotropic scattering, and (c) a phenomenological assessment of its potential for ultra-high-energy cosmic-ray production and the origin of the recently detected TeV emission in large-scale AGN jets based on detailed source modelling. We expect these results to decisively advance our conceptual understanding of cosmic particle acceleration and to allow a qualified judgement of its phenomenological implications. As such the results are expected to become the central reference for further studies.

• DFG Programme: Research Grants
• International Connection: China, France, Ireland, Spain
• Cooperation Partners: Professor Peter Duffy; Professor Martin Lemoine; Professor Manel Perucho Pla; Professor Liu Ruoyu