TAPIR Seminar

Friday, May 14, 2021
2:00pm to 3:00pm
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Online Event
Ultra-High-Energy Cosmic Rays and Neutrinos from relativistic jets of Active Galactic Nuclei
Rostom Mbarek, Graduate Student, Department of Astronomy and Astrophysics, The University of Chicago,

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https://caltech.zoom.us/j/92271559087?pwd=TFQ2YVk2N0FpSzhlR3JvZlFENTUyQT09

We propagate particles in a 3D magnetohydrodynamic simulation of a relativistic jet to investigate the espresso mechanism, a one-shot reacceleration of lower-energy cosmic rays that may lead to the production of ultra-high-energy cosmic rays (UHECRs) in active galactic nuclei (Mbarek & Caprioli 2019).  We find spectra, chemical composition, and anisotropy consistent with UHECR phenomenology. In this work, we also include UHECR diffusion, photodisintegration, and neutrino production. Initially, we include sub-grid scattering to account for small scale magnetic fluctuations to test for the relative importance of espresso and stochastic acceleration. Then, we study high-energy neutrino production, taking into account the effects of external photon fields, and incorporate the effects of photodisintegration and the production of secondary particles. We find that the scattering rate increases the acceleration efficiency of lower-energy particles up to a factor of ~104 and flattens the spectrum of escaping particles. However, the highest-energy particles are still espresso-accelerated even for Bohm diffusion. The neutrino spectrum we obtain is compared with IceCube's observed flux.

For more information, please contact JoAnn Boyd by email at joann@caltech.edu.