Year: 2025
Type: conference-paper
Abstract: We analyze the cosmic-ray Moon and Sun shadows observed by the ALPAQUITA air shower array between April 2023 and April 2024. The Moon shadow is successfully detected with a statistical significance of $-10\sigma$, as expected. The Sun shadow is also observed with a statistical significance of $-5\sigma$ during a period near the solar maximum. The deficit ratio relative to the cosmic-ray background is estimated to be approximately 1%, which is approximately half that of the Moon shadow. This smaller deficit is attributed to the scattering of cosmic rays by the multipolar coronal magnetic fields surrounding the Sun during the active phase. We will continue to monitor the Sun shadow throughout Solar Cycle 25 with the ALPAQUITA and future ALPACA experiments, in order to investigate the temporal variation of the solar magnetic field.
DOI: 10.22323/1.501.1308
Author: Kazumasa Kawata
Language: English
Subfield: Nuclear and High Energy Physics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Awards: Challenges in Space Weather Prediction Using the Sun's Shadow in the Cosmic Rays, Measurement of cosmic-ray proton energy spectrum to test the standard model of galactic cosmic-ray origin, Gamma Ray Astronomy at Highest Energy in the Southern Hemisphere, G373756783, Novel Development of Highest Energy Gamma Ray Astronomy, Unravelling mystery of cosmic particle accelerator PeVatron by highest-energy gamma-ray observation, 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: W4414451079
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