Real-time monitoring of the rigidity spectrum of large Forbush decreases in May and October 2024 with the paired neutron monitor and muon detector at the Antarctic Syowa Station
Issued Date
2026-12-01
Resource Type
ISSN
13438832
eISSN
18805981
Scopus ID
2-s2.0-105036359191
Journal Title
Earth Planets and Space
Volume
78
Issue
1
Rights Holder(s)
SCOPUS
Bibliographic Citation
Earth Planets and Space Vol.78 No.1 (2026)
Suggested Citation
Hayashi Y., Munakata K., Kozai M., Kataoka R., Kadokura A., Kato C., Miyashita N., Miyake S., Murase K., Duldig M.L., Ruffolo D., Mitthumsiri W., Muangha P., Sáiz A., Seunarine S., Evenson P.A., Mangeard P.S., Iwai K., Menjo H., Echer E., Lago A.D., Rockenbach M., Schuch N.J., Bageston J.V., Braga C.R., Jassar H.K.A., Sharma M.M., Burahmah N., Zaman F., Sabbah I., Kuwabara T., Chen D., Huang J. Real-time monitoring of the rigidity spectrum of large Forbush decreases in May and October 2024 with the paired neutron monitor and muon detector at the Antarctic Syowa Station. Earth Planets and Space Vol.78 No.1 (2026). doi:10.1186/s40623-026-02386-y Retrieved from: https://repository.li.mahidol.ac.th/handle/123456789/116381
Title
Real-time monitoring of the rigidity spectrum of large Forbush decreases in May and October 2024 with the paired neutron monitor and muon detector at the Antarctic Syowa Station
Author(s)
Hayashi Y.
Munakata K.
Kozai M.
Kataoka R.
Kadokura A.
Kato C.
Miyashita N.
Miyake S.
Murase K.
Duldig M.L.
Ruffolo D.
Mitthumsiri W.
Muangha P.
Sáiz A.
Seunarine S.
Evenson P.A.
Mangeard P.S.
Iwai K.
Menjo H.
Echer E.
Lago A.D.
Rockenbach M.
Schuch N.J.
Bageston J.V.
Braga C.R.
Jassar H.K.A.
Sharma M.M.
Burahmah N.
Zaman F.
Sabbah I.
Kuwabara T.
Chen D.
Huang J.
Munakata K.
Kozai M.
Kataoka R.
Kadokura A.
Kato C.
Miyashita N.
Miyake S.
Murase K.
Duldig M.L.
Ruffolo D.
Mitthumsiri W.
Muangha P.
Sáiz A.
Seunarine S.
Evenson P.A.
Mangeard P.S.
Iwai K.
Menjo H.
Echer E.
Lago A.D.
Rockenbach M.
Schuch N.J.
Bageston J.V.
Braga C.R.
Jassar H.K.A.
Sharma M.M.
Burahmah N.
Zaman F.
Sabbah I.
Kuwabara T.
Chen D.
Huang J.
Author's Affiliation
Nagoya University
University of Tasmania
Institute of High Energy Physics, Chinese Academy of Sciences
Shinshu University
Kuwait University
Johns Hopkins University Applied Physics Laboratory
National Astronomical Observatories Chinese Academy of Sciences
Instituto Nacional de Pesquisas Espaciais
Faculty of Science, Mahidol University
Okinawa Institute of Science and Technology Graduate University
Kitami Institute of Technology
The Bartol Research Institute
University of Wisconsin-River Falls
College of Technological Studies Kuwait
National Astronomical Research Institute of Thailand
National Institute of Technology, Gifu College
Joint Support-Center for Data Science Research
University of Tasmania
Institute of High Energy Physics, Chinese Academy of Sciences
Shinshu University
Kuwait University
Johns Hopkins University Applied Physics Laboratory
National Astronomical Observatories Chinese Academy of Sciences
Instituto Nacional de Pesquisas Espaciais
Faculty of Science, Mahidol University
Okinawa Institute of Science and Technology Graduate University
Kitami Institute of Technology
The Bartol Research Institute
University of Wisconsin-River Falls
College of Technological Studies Kuwait
National Astronomical Research Institute of Thailand
National Institute of Technology, Gifu College
Joint Support-Center for Data Science Research
Corresponding Author(s)
Other Contributor(s)
Abstract
Large Forbush decreases (FDs) in the Galactic cosmic ray flux were observed by the paired neutron monitor (SNM) and the vertical channel of the muon detector (SMDV) at the Antarctic Syowa Station in May and October, 2024. The maximum count rate depressions in SNM and SMDV are ∼10% and ∼5% in the May FD, respectively. In the October FD, the observed count rates decreased in two steps following two successive interplanetary shocks. The maximum count rate depression recorded by SNM (SMDV) is ∼7% (∼3%) in the first step, while it is ∼8% (∼5%) in the second step. It is demonstrated that the SNM count rate fraction relative to the total count rate in SNM and SMDV (Fn) is a good real-time indicator of the temporal variation of the cosmic ray rigidity spectrum (ΔΓ(P,t)), which is an important parameter for identifying the physical processes responsible for FD effects. It is verified that the variation of Fn is consistent with ΔΓ(P,t) calculated from the Global Fitting Analysis (GFA) at the Syowa Station. Fn also shows a significant increase of ΔΓ(P,t) during the ground-level enhancement (GLE) due to solar energetic particles on May 11 superposed on the FD recovery phase, implying that the total (Galactic + solar) cosmic ray spectrum is softened due to the contribution from GLE intensity steeply increasing with decreasing rigidity. This implies that Fn can be also a good indicator of small GLEs which are sometimes difficult to identify in the count rate variation when masked by an FD and the associated diurnal anisotropy. Graphic Abstract: (Figure presented.)