High-Energy Neutrino Emission in NGC1068 driven by Turbulent Magnetic Reconnection

Abstract

Astrophysical neutrinos from Active Galactic Nuclei (AGN) offer a unique window into high-energy particle acceleration in obscured environments. The nearby Type II Seyfert galaxy NGC 1068 is a compelling example, exhibiting evidence of a high-energy neutrino excess without an associated TeV $γ$-ray counterpart. This suggests that hadronic processes may occur within an inner, magnetically dominated region, where the TeV emission is suppressed by $γγ$ absorption and reprocessed via electromagnetic cascades in the dense, obscured environment. Building on our framework, which establishes turbulence-driven magnetic reconnection as the main driver for particle acceleration in this source, we present a refined lepto-hadronic model based on de Gouveia Dal Pino & Lazarian (2005) and Kadowaki et al. (2015). In these proceedings, we adopt a conservative inner disk radius compared to our previous results, moving the acceleration region further from the innermost stable circular orbit. We estimate the high-energy neutrino emission from hadronic and photo-hadronic processes, constrained by the acceleration timescale for first-order Fermi acceleration within the turbulent current sheet. The estimated model reproduces the IceCube neutrino flux excess, providing an essential technical complement and validation for our forthcoming comprehensive publication.

Figures (2)

• Figure 1: Hadronic Acceleration and Cooling Timescales. This plot illustrates the energetic competition between turbulence-driven reconnection particle acceleration and energy loss mechanisms for protons in the coronal reconnection layer. The first-order Fermi acceleration timescale ($t_{\rm acc}$) is represented by the blue solid horizontal line, confirming its energy-independent nature and high efficiency up to $1.4 \times 10^{18}\, \text{eV}$, where the proton Larmor radius approaches the current sheet width ($\Delta R_X$). Energy loss timescales include synchrotron radiation (green solid line), proton-proton ($t_{\rm pp}$, blue dot-dashed curve), and photo-hadronic interactions ($t_{p\gamma}$, purple dotted curve and Bethe-Heitler, orange dashed curve), which account for both disk blackbody and X-ray photon fields described in details in PassosReis_NGC_ICRC2025. The maximum proton energy achievable ($E_{\max}$) is determined by the intersection point where $t_{\rm acc}$ equals the sum of the total losses in our system $\sim 10^{14}\, \text{eV}$.
• Figure 2: High-energy neutrino emission modeled by the cascading of hadrons. The acceleration of protons up to the energies seen in Fig. \ref{['fig:cool_HAD']} allows protons to reach the energies required for subsequent hadronic and photo-hadronic interactions (cascading). These interactions produce the observed high-energy neutrinos modeled in this plot, constrained by $R_X \simeq 6\, R_{\rm Sch}$. The model successfully reproduces the observed IceCube neutrino flux 95% confidence region IceCube_2022 (shaded region in magenta), confirming the efficient hadronic acceleration by turbulent magnetic reconnection.