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arxiv: 2510.00648 · v1 · submitted 2025-10-01 · 🌌 astro-ph.HE

Diffuse neutrino flux from coronal magnetospheric current sheets of accreting black holes

Despina Karavola , Maria Petropoulou , Damiano F. G. Fiorillo , Luca Comisso , Lorenzo Sironi This is my paper

Pith reviewed 2026-05-18 10:59 UTC · model grok-4.3

classification 🌌 astro-ph.HE
keywords AGN coronaediffuse neutrinosblack hole magnetospherecurrent sheetsIceCubeneutrino fluxproton accelerationEddington ratio
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The pith

Protons accelerated in current sheets of AGN coronae produce a diffuse neutrino flux matching IceCube data when magnetization is fixed at 10^5.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper models neutrino production in the coronae of non-jetted AGN by accelerating protons in magnetospheric current sheets near the black hole. Two parameters govern the output: proton magnetization sets the peak neutrino energy while Eddington ratio sets how much energy reaches secondary particles. Integrating the model over an AGN population yields a predicted diffuse neutrino background. This background matches both the intensity and spectral slope reported by IceCube when the magnetization is set to the single value 10^5 for every source.

Core claim

Relativistic protons accelerated inside black-hole magnetospheric current sheets within AGN coronae generate neutrinos whose diffuse flux, after population synthesis, reproduces the IceCube measurements in both normalization and power-law index when the proton plasma magnetization is taken to be 10^5 across the entire sample.

What carries the argument

Magnetospheric current sheets whose proton plasma magnetization σ_p sets the maximum energy reached by accelerated protons and therefore the peak of the resulting neutrino spectrum.

If this is right

  • The observed diffuse neutrino background can be accounted for by non-jetted AGN alone.
  • The spectral shape of the neutrino flux is controlled almost entirely by the fixed magnetization value.
  • The overall flux normalization scales with the distribution of Eddington ratios across the AGN population.
  • Neutrino production is directly tied to the same plasma responsible for the hard X-ray corona emission.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • If the fixed-magnetization assumption holds, similar current-sheet acceleration should operate in other accreting compact objects whose coronae produce hard X-rays.
  • Individual bright AGN could become detectable neutrino point sources for next-generation telescopes if their Eddington ratios are high enough.
  • The model links the X-ray corona directly to high-energy neutrino output without requiring relativistic jets.

Load-bearing premise

The proton magnetization σ_p is the same fixed value of 10^5 in every AGN corona and is set by the same current-sheet physics independent of source properties.

What would settle it

An IceCube measurement or future neutrino observatory result showing that the diffuse neutrino spectrum has a slope or overall intensity clearly inconsistent with the value calculated for σ_p equal to 10^5 using the observed AGN luminosity function.

Figures

Figures reproduced from arXiv: 2510.00648 by Damiano F. G. Fiorillo, Despina Karavola, Lorenzo Sironi, Luca Comisso, Maria Petropoulou.

Figure 1
Figure 1. Figure 1: Scatter plots showing the X-ray luminosity distribution (panel a), the X-ray Eddington ratio (panel b), the black hole mass (panel c), and the X-ray flux (panel d) as a function of luminosity distance for sources from the BAT catalog (colored circles) and the mock AGN catalog (colored crosses). Color shows the black hole mass for both populations (see colorbars). by [14] which provides us with 677 non-blaz… view at source ↗
Figure 2
Figure 2. Figure 2: All-flavor neutrino energy flux of non-blazar AGN in the catalog of [14] for three 𝜎p values, namely 103 (top panel), 105 (middle panel) and 107 (bottom panel). Normalization scales as described by eq. 8. Colored curves show neutrino spectra from a sub-sample of the mock catalog. Colors represent the ratio 𝜆X,Edd. The dashed black line shows the sum of all sources while the dash-doted black one represents … view at source ↗
read the original abstract

Non-jetted AGN exhibit hard X-ray emission with a power law spectrum above $\sim$2 keV, which is thought to be produced through Comptonization of soft photons by electrons and positrons (pairs) in the vicinity of the black hole. The origin and composition of this plasma source, known as the corona, is a matter open for debate. Our study focuses on the role of relativistic protons accelerated in black-hole magnetospheric current sheets in the neutrino production of AGN coronae. We present a model that has two free parameters, namely the proton plasma magnetization $\sigma_{\rm p}$, which controls the peak energy of the neutrino spectrum, and the Eddington ratio $\lambda_{\rm Edd}$ (defined as the ratio between X-ray luminosity $L_{\rm X}$ and Eddington luminosity $L_{\rm Edd}$), which controls the amount of energy transferred to secondary particles. Furthermore, we combine our coronal model with an AGN population in order to provide a prediction for the diffuse neutrino flux measured on Earth. We compare our results with the observational data by IceCube and we find a satisfactory agreement on both the flux value and the slope of the neutrino distribution when we assume a $\sigma_{\rm p}$ value of $10^5$ for all the sources in our sample.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper models neutrino production in non-jetted AGN coronae through relativistic protons accelerated in black-hole magnetospheric current sheets. It introduces a two-parameter framework (proton plasma magnetization σ_p controlling neutrino peak energy, and Eddington ratio λ_Edd controlling energy transfer to secondaries), combines the coronal emission model with an AGN population synthesis, and reports that setting σ_p = 10^5 uniformly across all sources yields a diffuse neutrino flux whose normalization and spectral slope agree with IceCube data.

Significance. If the result holds after addressing parameter justification, the work would provide a concrete mechanism linking hard X-ray coronae to high-energy neutrinos, offering an alternative to jet-based models for the diffuse flux. The population-level integration and explicit two-parameter structure are strengths that could be developed into falsifiable predictions once σ_p is either derived from first principles or allowed to vary with source properties.

major comments (2)
  1. [Abstract and model description] Abstract and model description: the reported agreement with IceCube flux normalization and slope is obtained only after fixing σ_p = 10^5 for every source in the sample. The text states that this single value 'controls the peak energy of the neutrino spectrum' and is assumed uniform independent of λ_Edd or black-hole mass; no derivation from reconnection rate, pair loading, or magnetospheric structure is provided to justify universality. Because the integrated flux and spectral index shift if σ_p varies across the population, this choice is load-bearing for the central claim of satisfactory agreement.
  2. [Population synthesis and results] Population synthesis section: the paper does not show how the diffuse flux changes when σ_p is drawn from a distribution motivated by current-sheet physics rather than held fixed. A sensitivity test or error propagation on σ_p would be required to establish whether the match to IceCube is robust or an artifact of the uniform choice.
minor comments (2)
  1. [Introduction] Notation for σ_p and λ_Edd should be defined at first use with explicit units or dimensionless status; the current introduction leaves the physical meaning of the magnetization parameter implicit for readers outside the reconnection literature.
  2. [Figures] Figure captions for the neutrino spectrum plots should state the exact value of σ_p used and whether the curves include the full population integration or a single-source template.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their thoughtful comments on our manuscript. The referee correctly identifies that our central result relies on the choice of a uniform proton magnetization σ_p = 10^5. We address this and the request for sensitivity tests in detail below. We will revise the manuscript to include additional discussion and analysis as outlined in our responses.

read point-by-point responses

  1. Referee: [Abstract and model description] Abstract and model description: the reported agreement with IceCube flux normalization and slope is obtained only after fixing σ_p = 10^5 for every source in the sample. The text states that this single value 'controls the peak energy of the neutrino spectrum' and is assumed uniform independent of λ_Edd or black-hole mass; no derivation from reconnection rate, pair loading, or magnetospheric structure is provided to justify universality. Because the integrated flux and spectral index shift if σ_p varies across the population, this choice is load-bearing for the central claim of satisfactory agreement.

    Authors: We agree that the agreement with IceCube data is achieved with a fixed value of σ_p = 10^5 across the population, and that this parameter choice is central to the result. In the current version, σ_p is treated as a free parameter that sets the characteristic energy scale for proton acceleration in current sheets, motivated by the requirement that the resulting neutrino spectrum peaks in the TeV-PeV range relevant for IceCube. While we do not provide a first-principles derivation of why this value should be universal, we note that it corresponds to a plausible magnetization in the corona where magnetic energy density greatly exceeds the rest-mass energy density of protons. In the revised manuscript, we will add a dedicated paragraph discussing the physical motivation for this choice, referencing reconnection studies in similar environments, and explicitly state that it is assumed constant as a baseline model. We will also note that future work could explore dependencies on source properties. revision: partial

  2. Referee: [Population synthesis and results] Population synthesis section: the paper does not show how the diffuse flux changes when σ_p is drawn from a distribution motivated by current-sheet physics rather than held fixed. A sensitivity test or error propagation on σ_p would be required to establish whether the match to IceCube is robust or an artifact of the uniform choice.

    Authors: We acknowledge the value of demonstrating robustness against variations in σ_p. Although the manuscript presents results for the fiducial uniform value, we agree that a sensitivity study is warranted. In the revised version, we will add a new subsection or figure showing the diffuse neutrino flux for σ_p varied by factors of a few (e.g., 10^4 to 10^6) and for a simple distribution such as a log-normal with mean 10^5 and dispersion 0.5 dex. This will illustrate the range of possible fluxes and confirm that the spectral slope remains compatible with IceCube data within reasonable variations. revision: yes

Circularity Check

1 steps flagged

Diffuse flux agreement with IceCube holds only after fixing σ_p=10^5 uniformly across sources

specific steps
  1. fitted input called prediction [Abstract]
    "We compare our results with the observational data by IceCube and we find a satisfactory agreement on both the flux value and the slope of the neutrino distribution when we assume a σ_p value of 10^5 for all the sources in our sample."

    σ_p is introduced as a free parameter that directly sets the peak energy of the neutrino spectrum. The paper reports agreement with data specifically under the assumption that this parameter equals 10^5 for the entire population; the flux and slope match is therefore produced by the choice of the fitted input rather than derived independently from magnetospheric current-sheet equations.

full rationale

The paper's central result is a population-integrated prediction for the diffuse neutrino flux that reproduces both normalization and slope of IceCube data. This match is obtained by adopting a single fixed value σ_p=10^5 for every AGN in the sample, a choice the abstract explicitly states controls the peak neutrino energy. The model description identifies σ_p as one of two free parameters with no first-principles derivation supplied for its universality. Consequently the reported agreement reduces to a tuned input rather than an independent output of the current-sheet physics. The population synthesis and reconnection framework retain independent content, preventing a higher circularity score.

Axiom & Free-Parameter Ledger

2 free parameters · 1 axioms · 0 invented entities

The model rests on two free parameters whose values are either fitted or chosen to match data, plus domain assumptions about particle acceleration whose independent support is not shown in the abstract.

free parameters (2)
  • proton plasma magnetization σ_p = 10^5
    Controls the peak energy of the neutrino spectrum and is set to 10^5 to obtain agreement with IceCube flux and slope.
  • Eddington ratio λ_Edd
    Controls the fraction of energy transferred to secondary particles; treated as a free parameter in the model.
axioms (1)
  • domain assumption Relativistic protons are accelerated to high energies in black-hole magnetospheric current sheets within the corona
    This is the central physical mechanism invoked for neutrino production; invoked in the model setup.

pith-pipeline@v0.9.0 · 5780 in / 1439 out tokens · 35606 ms · 2026-05-18T10:59:25.987693+00:00 · methodology

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Lean theorems connected to this paper

Citations machine-checked in the Pith Canon. Every link opens the source theorem in the public Lean library.

  • IndisputableMonolith/Cost/FunctionalEquation.lean washburn_uniqueness_aczel unclear
    ?
    unclear

    Relation between the paper passage and the cited Recognition theorem.

    We present a model that has two free parameters, namely the proton plasma magnetization σ_p, which controls the peak energy of the neutrino spectrum, and the Eddington ratio λ_Edd ... we find a satisfactory agreement ... when we assume a σ_p value of 10^5 for all the sources in our sample.

  • IndisputableMonolith/Foundation/RealityFromDistinction.lean reality_from_one_distinction unclear
    ?
    unclear

    Relation between the paper passage and the cited Recognition theorem.

    Magnetic reconnection ... can accelerate a fraction of the aforementioned protons to highly relativistic energies ... protons may interact with coronal X-ray photons and produce neutrinos through photohadronic (pγ) interactions.

What do these tags mean?
matches
The paper's claim is directly supported by a theorem in the formal canon.
supports
The theorem supports part of the paper's argument, but the paper may add assumptions or extra steps.
extends
The paper goes beyond the formal theorem; the theorem is a base layer rather than the whole result.
uses
The paper appears to rely on the theorem as machinery.
contradicts
The paper's claim conflicts with a theorem or certificate in the canon.
unclear
Pith found a possible connection, but the passage is too broad, indirect, or ambiguous to say the theorem truly supports the claim.

Reference graph

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