Observation of the Forbush Decrease on 2024 May 10, Using the ALPAQUITA Air-shower Array at the 70–1000 GV Rigidity Range
Year: 2026
Type: article
Abstract: The Andes Large area PArticle detector for Cosmic ray physics and Astronomy is a new air-shower array experiment under construction in the Bolivian Andes, and its prototype ALPAQUITA surface array has been operating since 2023 April. In addition to the traditional ≥ 3-hit or ≥ 4-hit coincidences to trigger recording air-shower events, ALPAQUITA records the counting rates of the ≥ 1-hit and ≥ 2-hit events (Any1 and Any2, respectively). We report a successful detection of a Forbush decrease (FD) that occurred on 2024 May 10 caused by a passage of an interplanetary shock formed ahead of the interplanetary coronal mass ejection. The amplitude detected in the Any1 rate is 4.26% ± 0.33% at the median primary rigidity of 76 GV, which is consistent with the observations with the worldwide neutron monitor and muon detector networks. Under the assumption of a power-law rigidity spectrum, we renormalized the errors of the observed amplitude ( A obs ) and fitted them as a function of the median primary rigidity ( R m ) of each detector and observational method. The result A obs = ( 10.9 % ± 0.9 % ) × ( R m / 10 GV ) − 0.55 ± 0.07 exhibits the hard nature of this event. Our nondetection in the Any2 rate decrease constrains the amplitude with a 2 σ upper limit to be 0.95% at 960 GV. This marginally suggests an existence of a spectral softening between 100 and 1000 GV, as also suggested by the Misato underground muon detector at 145 GV. Although a strong geomagnetic storm was observed during this period, we conclude it does not impact our results. Our novel technique realizes a unique coverage to study the behavior of the FDs at the highest rigidity.
Source: The Astrophysical Journal
Authors: M. Anzorena, E. de la Fuente, K. Fujita, R. Garcia, Y. Hayashi, K. Hibino, N. Hotta, G. Imaizumi, Y. Katayose, C. Kato, S. Kato, T. Kawashima, K. Kawata, M. Kobayashi, S. Kobayashi, T. Koi, H. Kojima, P. Miranda, S. Mitsuishi, A. Mizuno, K. Munakata, Y. Nakamura, M. Nishizawa, Y. Noguchi, S. Ogio, M. Ohishi, M. Ohnishi, A. Oshima, M. Raljevic, H. Rivera, T. Saito, T. Sako, T. K. Sako, S. Shibata, A. Shiomi, M. Subieta, F. Sugimoto, N. Tajima, W. Takano, Y. Takeyama, M. Takita, N. Tamaki, Y. Tameda, K. Tanaka, R. Ticona, H. Tsuchiya, Y. Tsunesada, S. Udo, G. Yamagishi, Y. Yamanaka, K. Yamazaki, Y. Yokoe
Institutions: Institute for Cosmic Ray Research, The University of Tokyo, Universidad de Guadalajara, RIKEN, Shinshu University, Kanagawa University, Utsunomiya University, Yokohama National University, Centre National de la Recherche Scientifique, Institut d'Astrophysique de Paris, Sorbonne Université, Chubu University, Universidad Mayor de San Andrés, National Institute of Informatics, Tokyo Metropolitan College of Industrial Technology, Nagano Prefectural Institute of Technology, Nihon University, Osaka Electro-Communication University, Hiroshima City University, Japan Atomic Energy Agency, Osaka Metropolitan University, Nambu Yoichiro Institute of Theoretical and Experimental Physics, Osaka Metropolitan University
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Awards: Challenges in Space Weather Prediction Using the Sun's Shadow in the Cosmic Rays, G1374949450, Measurement of cosmic-ray proton energy spectrum to test the standard model of galactic cosmic-ray origin, Real-Time database for high resolution Neutron Monitor measurements, 都市「新中間層」の職業特性とその生活意識に関する実証的研究, Gamma Ray Astronomy at Highest Energy in the Southern Hemisphere, G373756783, Novel Development of Highest Energy Gamma Ray Astronomy, 高密度ASアレイを用いた銀河中心方向からの10TeV領域宇宙ガンマ線天体の研究, Unravelling mystery of cosmic particle accelerator PeVatron by highest-energy gamma-ray observation, G6141822678, G7080048889, Origin of galactic cosmic rays revealed by observations of ultra-high cosmic gamma rays in the southern hemisphere, Demonstration of 100 TeV gamma-ray observation in the southern hemisphere
OpenAlex ID: W7127050230