{
  "abstract": "Discrete curvatures of visibility graphs are increasingly used as descriptors of geophysical time series, but their response to a transient has rarely been calibrated against the simplest properties of that transient. We carry out this calibration for the nodal Forman--Ricci curvature $\\mathcal{F}$ of natural visibility graphs applied to neutron-monitor records of the Gannon storm (2024 May 10--11) and the 2025 June 1 Forbush decrease (FD), the two largest FDs of solar cycle 25, using 30-min NMDB data from six NM64 stations ($R_c \\simeq 0$--$7$~GV), i.e.\\ twelve station--event series. Curvature collapses at FD onset in every series (Cliff's $δ= 0.63$--$1.0$), but a 6-h running standard deviation separates onset from quiet time more strongly (mean $δ= 0.96$ vs $0.89$; mean block-permutation displacement $z = -27$ vs $-14$). Injecting synthetic decreases into the real pre-event records of each station shows that the curvature extreme follows $|\\mathcal{F}_{\\min}| \\propto (A/σ)^{0.50}$ ($R^2 = 0.88$), where $A$ is the FD amplitude and $σ$ the station's quiet-time noise, and is independent of the duration of the main phase (exponent $0.006$ over 3--36~h). With $A$, $σ$ and the main-phase duration of each series as the only inputs, the calibration predicts the twelve observed extremes with standardized residuals of mean $-0.26$ and standard deviation $0.94$, and the observed extremes correlate with $A/σ$ at Spearman $ρ= 0.95$. Within the precision allowed by these data, nodal Forman--Ricci curvature of the whole-series visibility graph carries no information about these FDs beyond their amplitude relative to station noise; in particular, it does not distinguish the single-step Gannon decrease from the two-step June 2025 decrease.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2607.13236",
  "author_total": 1,
  "authors": [
    {
      "name": "D. Sierra-Porta"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/53ahb47jb1e3n.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2607.13236",
  "fulltext_url": null,
  "id": "53ahb47jb1e3n",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2607.13236",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.EP"
    ],
    [
      "arxiv",
      "astro-ph.IM"
    ],
    [
      "arxiv",
      "astro-ph.SR"
    ],
    [
      "openalex",
      "3103|Solar and Space Plasma Dynamics"
    ]
  ],
  "openalex": "W7169151266",
  "pdf_url": "https://arxiv.org/pdf/2607.13236",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-23",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/53ahb47jb1e3n.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:35:15Z",
      "native_id": "2607.13236",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2607.13236"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.IM",
      "subfield": "instrumentation-methods"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.EP",
      "subfield": "planetary"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.SR",
      "subfield": "stellar"
    }
  ],
  "title": "What visibility-graph curvature measures in Forbush decreases: a calibration on the two largest events of solar cycle 25",
  "title_text": "What visibility-graph curvature measures in Forbush decreases: a calibration on the two largest events of solar cycle 25",
  "type": "preprint",
  "updated_at": "2026-10-30T12:35:15Z",
  "url": "https://research.draconitic.com/paper/53ahb47jb1e3n",
  "venue": "arXiv",
  "versions": []
}