WoU-MMA: Pinning the Generation of Ultra-High-Energy Cosmic Rays with First Principles Plasma Simulations

This award supports a study of how highest energy cosmic rays can be accelerated to the energies we measure these particles to have. The origin of Ultra-High-Energy Cosmic Rays (UHECRs) has remained an unsolved question of high energy astrophysics from several decades. It is generally believed that extragalactic sources in the nearby universe are responsible for producing these cosmic rays with extremely high energies. Active galactic nuclei are generally suggested as the most promising sources of UHECRs. However, our theoretical understanding of the processes that can accelerate UHECRs in active galactic nuclei lags far behind the observational progress. This project will perform advanced computer simulations that model the acceleration of particles at the microscopic level with high accuracy and detail. By studying the properties of the accelerated charged particles and the associated gamma-rays and neutrinos, this research will contribute to interpreting current and future observations and ultimately provide insights into the origin of the highest energy cosmic rays. In doing so, the project addresses goals of NSF's "Windows on the Universe: The Era of Multi-Messenger Astrophysics" program. The research plan focuses on developing state-of-the-art fully kinetic simulations of plasma turbulence in magnetically dominated environments, taking into account cooling losses from synchrotron and inverse Compton radiation, as well as photo-hadronic interactions. The main goal of this project is to achieve a better understanding of the physics of cosmic ray acceleration, as well as the simultaneous energization of electrons and positrons within plasma turbulence and magnetic reconnection sites. The designed supercomputer simulations will not only produce self-consistent energy distributions of the accelerated particles, but also allow for the exploration of the relationship between the particle distributions and the key physical parameters that regulate the particle energization process. Physically-grounded predictions for the acceleration of UHECRs, the photon spectrum, and neutrino emission associated with turbulent energy dissipation in relativistic jets and coronae of active galactic nuclei will be produced by this research project. The predictions will aid in the interpretation of current and future multi-messenger observations, contributing to our understanding of the origin of UHECRs. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.