Solar neutron and muon detection on November 11, 2025: First simultaneous recovery of energy spectra

TL;DR

This paper reports the first simultaneous measurement of energy spectra of atmospheric neutrons and muons during a solar energetic particle event, revealing spectral evolution and demonstrating the capabilities of the Aragats Solar Neutron Telescope.

Contribution

It presents the first simultaneous detection and spectral analysis of neutrons and muons during a solar event, showing spectral evolution over time.

Findings

Detection of a dual-peak profile in neutron and muon fluxes.

Spectral indices decline with energy, indicating evolving acceleration conditions.

First measurement of atmospheric neutron and muon spectra in the 10-600 MeV range during a solar event.

Abstract

Ground Level Enhancement (GLE) events provide rare opportunities to study high-energy solar particle acceleration through direct detection of secondary radiation at ground level. On November 11, 2025, the Aragats Solar Neutron Telescope (ASNT) recorded a statistically significant increase in high-energy neutron and muon fluxes associated with an X5.1 flare and the subsequent Solar Energetic Proton (SEP) event. The event displayed a unique dual-peak profile: an initial hard component at 10 28 UT, followed by a softer yet still energetic peak at 10 45 UT. For the first time, we report simultaneous energy spectra of atmospheric neutrons and muons measured in the 10 600 MeV range at Aragats. Broken-power-law fits reveal a clear temporal evolution of acceleration conditions, evidenced by spectral indices declining with energy. These findings highlight the unique capabilities of the ASNT as an instrument for studying extreme solar particle acceleration.