Resolving GLE 77 of November 11, 2025: First Simultaneous Recovery of Neutron and Muon Energy Spectra

Abstract Ground Level Enhancements (GLEs) are rare solar energetic particle events in which relativistic solar protons produce measurable increases in secondary neutrons and muons at the ground level. For space weather operations, the key real‐time measurement is the spectral hardness of the solar proton population. This indicates that the SEP protons extend far enough to include substantial fluxes above 50 MeV, posing risks to satellite electronics, electrical lines, and pipelines on Earth. We analyze GLE 77 (11 November 2025) using measurements from Aragats (3,200 m) at the Aragats Solar Neutron Telescope (ASNT) and the SEVAN Light spectrometric detector. We employ energy‐deposit histograms of simultaneously detected muon‐ and neutron‐enriched fluxes to recover differential energy spectra and derive the muon‐to‐neutron ratio. The spectra are compared with a unified forward‐modeling chain (CORSIKA atmospheric cascades and GEANT4 detector response) processed through the same reconstruction procedure as the data. Both instruments reveal a two‐peak temporal structure that coincides with neutron monitor observations. The observations are most consistent with a dominant contribution from primary protons near 9–10 GeV, that is, near and slightly above the local geomagnetic cutoff. These neutron–muon spectrometric diagnostics offer a practical method for near‐real‐time tracking of proton spectral hardness during future GLEs.