The Influence of Sun's and Moon's Shadows on Cosmic-Ray Anisotropy

Abstract

Large-scale anisotropy, with amplitudes reaching approximately 0.1% at TeV energies, has been observed by multiple cosmic-ray experiments. The obstruction of cosmic rays by the Sun and Moon creates shadow effects, potentially impacting the observed cosmic ray anisotropy. To evaluate these effects, this study calculates the contributions of the Sun's and Moon's shadows to the overall cosmic-ray anisotropy in both local solar and sidereal time. The analysis reveals that in local sidereal time, the total 1D projection amplitude of the anisotropy is around 0.003%, which is significantly smaller than the observed cosmic-ray anisotropy. This indicates that the influence of the Sun's and Moon's shadows on cosmic-ray anisotropy analysis in local sidereal time is negligible. In contrast, in local solar time, the shadow-induced deficit appears in a very small time bin, with a magnitude comparable to that of the cosmic-ray solar anisotropy. This deficit could serve as a benchmark for validating anisotropy measurements in future facilities.

15 pages, 8 figures

References in corpus (8)

• Observation of a Large-scale Anisotropy in the Arrival Directions of Cosmic Rays above $8\times 10^{18}$ eV
• Anisotropy and Corotation of Galactic Cosmic Rays
• The Large Scale Cosmic-Ray Anisotropy as Observed with Milagro
• Evolution of the cosmic ray anisotropy above 10^{14} eV
• Observation of Cosmic Ray Anisotropy with the IceTop Air Shower Array
• Northern sky Galactic Cosmic Ray anisotropy between 10-1000 TeV with the Tibet Air Shower Array
• Observation of the Cosmic Ray Moon shadowing effect with ARGO-YBJ
• Observation of the cosmic ray shadow of the Sun with the ANTARES neutrino telescope