Ground-based Observations of Temporal Variation of the Cosmic-Ray Spectrum during Forbush Decreases

Ground-based Observations of Temporal Variation of the Cosmic-Ray Spectrum during Forbush Decreases

Observations of temporary Forbush decreases (FDs) in the Galactic cosmic-ray (GCR) flux due to the passage of solar storms are useful for space-weather studies and alerts. Here, we introduce techniques that use global networks of ground-based neutron monitors and muon detectors to measure variations...

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Main Authors: W. Mitthumsiri, D. Ruffolo, K. Munakata, M. Kozai, Y. Hayashi, C. Kato, P. Muangha, A. Sáiz, P. Evenson, P.-S. Mangeard, J. Clem, S. Seunarine, W. Nuntiyakul, N. Miyashita, R. Kataoka, A. Kadokura, S. Miyake, K. Iwai, H. Menjo, E. Echer, A. Dal Lago, M. Rockenbach, N. J. Schuch, J. V. Bageston, C. R. Braga, H. K. Al Jassar, M. M. Sharma, N. Burahmah, F. Zaman, M. L. Duldig, I. Sabbah, T. Kuwabara
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal Letters
Subjects:
Forbush effect
Cosmic rays
Space weather
Cosmic ray detectors
Solar-terrestrial interactions
Online Access:https://doi.org/10.3847/2041-8213/add7d1
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Summary:Observations of temporary Forbush decreases (FDs) in the Galactic cosmic-ray (GCR) flux due to the passage of solar storms are useful for space-weather studies and alerts. Here, we introduce techniques that use global networks of ground-based neutron monitors and muon detectors to measure variations of GCR rigidity spectra in space during FDs by (1) fitting count rate decreases for power-law rigidity spectra in space with anisotropy up to second order and (2) using the “leader fraction” derived from a single neutron monitor. We demonstrate that both provide consistent results for hourly spectral index variations for five major FDs, and they agree with daily space-based data when available from the Alpha Magnetic Spectrometer. We have also made the neutron monitor leader fraction publicly available in real time. This work verifies that ground-based observations can be used to precisely monitor GCR spectral variation over a wide range of rigidities during space-weather events, with results in real time or from short-term postanalysis.
ISSN:2041-8205

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