Horizon 1 1 17 ACL : Articles dans des revues avec comité de lecture répertoriées par l'AERES Journal of Atmospheric and Solar-Terrestrial Physics 106690 [12 p.] Cosmic ray Atmospheric radiation environment Neutron spectrometer PIRATA oceanographic cruises ATLANTIQUE ZONE TROPICALE 2026 fdi:010095863 ENG Journal of Atmospheric and Solar-Terrestrial Physics 1364-6826 ISI:001631701200002 10.1016/j.jastp.2025.106690 https://www.documentation.ird.fr/hor/fdi:010095863 https://www.documentation.ird.fr/intranet/publi/2026-01/010095863.pdf 278 Horizon (IRD) This paper presents the operation of a neutron spectrometer onboard the R/V La Thalassa during the PIRATA (Prediction and Research Moored Array in the Tropical Atlantic) oceanographic cruises in the equatorial Atlantic. The cruises took place from February to April in 2019 and 2020. We analyze cosmic ray-induced neutrons measured by the spectrometer, accounting for various physical factors influencing neutron detection, including environmental and systematic effects primarily driven by atmospheric pressure and water vapor content variations. Additionally, the study incorporates the influence of short-term fluctuations in primary cosmic rays to investigate the geomagnetic cutoff rigidity dependence. Detailed analyses of count rates, fluxes, and neutron spectra are provided, facilitating cross-comparison of radiation fields. The mobile neutron spectrometer enables latitude-dependent surveys, assessing the impact of geomagnetic cutoff rigidity on neutron spectra. Equivalent 3NM64 count rates were derived from PIRATA measurements and compared with previous results. 020 ; 021 ; 030