Speaker
Description
Turbulent particle acceleration is widely invoked to explain high-energy emission from extreme astrophysical sources. However, standard second-order Fermi models based on Fokker–Planck equation neglect complex non-linear effects emerging in the high-amplitude ($\delta B/B \sim 1$) and relativistic turbulence regimes, expected in many astrophysical environments. Recent MHD and PIC simulations of turbulence have revealed that particle energization under such conditions is dominated by non-resonant processes and is highly intermittent, proceeding through abrupt, localized, large-magnitude energy jumps. This phenomenology cannot be described within diffusion-coefficient-based approaches, and remains largely unexplored in astrophysical applications. We present STRIPE (Strong-Turbulence Relativistic Intermittent Particle Energization), a new Monte Carlo code implementing and extending the novel theoretical framework of Lemoine (2022) for turbulent acceleration in the high-amplitude regime. STRIPE computes stochastic evolution of particle momentum driven by random velocity-gradient fluctuations and includes synchrotron and inverse-Compton losses self-consistently. Combined with our radiation module, the framework provides time-dependent particle spectra and broadband SED predictions. We apply STRIPE to conditions characteristic of extreme blazars and LHAASO-detected PeVatron microquasars. The resulting particle spectra are found to strongly deviate from standard diffusion-coefficient-based predictions: relativistic high-amplitude turbulence naturally produces hard, extended power-law tails without curvature, reaching multi-PeV energies. The combined model is able to reproduce key spectral properties of these two source classes. In a first full modeling application, we successfully fit the TeV–PeV gamma-ray spectrum of V4641 Sgr, including its unusually hard spectral index. STRIPE provides a new open computational tool for exploring turbulent acceleration in a multi-messenger context, with planned extensions toward hadronic emission and neutrino-flux predictions for extreme astrophysical accelerators.
