Abstract

We present the precision measurement of the daily proton fluxes in cosmic rays from May 20, 2011 to October 29, 2019 (a total of 2824days or 114 Bartels rotations) in the rigidity interval from 1 to 100GV based on 5.5×10^{9} protons collected with the Alpha Magnetic Spectrometer aboard the International Space Station. The proton fluxes exhibit variations on multiple timescales. From 2014 to 2018, we observed recurrent flux variations with a period of 27days. Shorter periods of 9days and 13.5days are observed in 2016. The strength of all three periodicities changes with time and rigidity. The rigidity dependence of the 27-day periodicity is different from the rigidity dependences of 9-day and 13.5-day periods. Unexpectedly, the strength of 9-day and 13.5-day periodicities increases with increasing rigidities up to ∼10 GV and ∼20 GV, respectively. Then the strength of the periodicities decreases with increasing rigidity up to 100GV.

Highlights

  • 12IPST, University of Maryland, College Park, Maryland 20742, USA 13CHEP, Kyungpook National University, 41566 Daegu, Korea 14CNR–IROE, 50125 Firenze, Italy

  • 100 GV based on 5.5 × 109 protons collected with the

  • The rigidity dependence of the 27-day periodicity is different from the rigidity dependences of 9-day

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Summary

Published by the American Physical Society

We present the precision measurement of the daily proton fluxes in cosmic rays from May 20, 2011 to October 29, 2019 (a total of 2824 days or 114 Bartels rotations) in the rigidity interval from 1 to 100 GV based on 5.5 × 109 protons collected with the Alpha Magnetic Spectrometer aboard the International Space Station. [11], generally concluded that the power of the periodicity decreases with increasing rigidity This formed the paradigm over the AMS rigidity range (1 to 100 GV) that the strength of the 27-day (and 13.5-day, 9-day) periodicities steadily decreases with increasing rigidity of cosmic rays, differently in solar maximum and minimum [16]. The Alpha Magnetic Spectrometer (AMS) has reported the time dependence of proton and helium fluxes on the timescale of Bartels rotations (BR: 27 days) [17]. Data analysis.—The daily isotropic flux Φji in the ith rigidity bin ðRi; Ri þ ΔRiÞ and jth day is given by

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