Observation of Forbush Decreases and GLE‐74 Recorded During Ground‐Level Neutron Monitoring Survey From Various Sites

Mashao, D. C. and Alton, T. L. and Baird, F. and Binnersley, C. L. and Bradnam, S. and Croft, S. and Joyce, M. J. and Packer, L. and Ryden, K. and Turner, T. and Wild, J. A. and Aspinall, M. D. (2026) Observation of Forbush Decreases and GLE‐74 Recorded During Ground‐Level Neutron Monitoring Survey From Various Sites. Space Weather, 24 (4): e2026SW004. ISSN 1542-7390

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Abstract

Plain Language Summary: Space weather events pose a great risk to critical infrastructures such as radio communication, satellite operations, electrical power grids, and aviation technology. The UK has registered severe space weather events as a potential risk to critical infrastructure. The UK designed and built a new standard ground‐level neutron monitor called NM‐2023 for severe space weather radiation assessment. A 4‐NM‐2023 matches the performance of a 6‐NM‐64 design but with a reduced footprint, volume, mass, and cost, utilizing environmentally friendly, non‐toxic gas‐filled counters. We present neutron monitoring survey results from N50L neutron slab‐based subsystems (from now on referred as N50L subsystems) deployed across several UK sites and the University of Surrey's Compact Neutron Monitor (CNM). The N50L subsystems and CNM provide data that have similar trends to the data from DRBS and Oulu, despite both being significantly smaller. The count rate measurements are influenced by altitude, latitude, and objects around the NM. The N50L subsystems, 2‐NM‐2023, DRBS, and Oulu were able to observe the Forbush decrease which occurred over the 2024 spring. However, only Oulu registered sufficient cosmic ray counts to be classified as GLE‐74, classified as a weak GLE.