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21.06.2024 / 10:30 / Zeuthen, SR 5 | Villa
Astroparticle Physics SeminarHigh-energy neutrinos from NGC 1068 probing proton acceleration in AGN coronae
Damiano Fiorillo
The recent discovery of astrophysical neutrinos from the Seyfert galaxy NGC 1068 suggests the presence of nonthermal protons within a compact “coronal” region close to the central black hole. The acceleration mechanism of these nonthermal protons remains elusive. In this talk, I discuss two alternative scenarios, in which acceleration is driven by either magnetic reconnection or strong magnetic turbulence. In the magnetic reconnection scenario, a large-scale reconnection layer in the pair-dominated corona accelerates protons until they reach global equipartition with the magnetic field and X-ray energy density. Guided by recent particle-in-cell (PIC) simulations of reconnection, we show that this picture can explain the soft power-law spectrum observed by IceCube, provided that the reconnection layer presents a sizable guide field. In the magnetic turbulence scenario, we consider for the first time that acceleration is not gyroresonant, as confirmed by recent PIC simulations, so that protons are accelerated over a roughly energy-independent timescale. We find that strong magnetized turbulence, with the turbulent magnetic energy density roughly equal to 1-10% of the rest mass energy density, naturally explains the normalization of the IceCube neutrino flux. Only a fraction of the protons in the corona, directly inferred from the neutrino spectrum, are accelerated to high-energies, so that the neutrinos signal from NGC 1068 is a direct testbed for particle acceleration in turbulence.
More Information: https://indico.desy.de/category/698/
