# Periodicities in the Daily Proton Fluxes from 2011 to 2019 Measured by the Alpha Magnetic Spectrometer on the International Space Station from 1 to 100 GV

Phys. Rev. Lett. 127, 271102 (2021)
Published on:
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 2824 days or 114 Bartels rotations) in the rigidity interval from 1 to 100 GV based on $5.5 \times 10^9$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 27 days. Shorter periods of 9 days and 13.5 days 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 $\sim 10 \textrm{GV}$ and $\sim 20 \textrm{GV}$, respectively. Then the strength of the periodicities decreases with increasing rigidity up to 100 GV.

Supplemental Material
In the following tables we present the daily proton flux $\Phi_p$ as a function of rigidity at the top of AMS. The fluxes are in units of $[{\rm m}^2 \cdot {\rm sr} \cdot {\rm s} \cdot {\rm GV}]^{-1}$. The errors include statistics ($\sigma_{\rm stat.}$), time-dependent systematic errors ($\sigma_{\rm time}$) and the total systematic error ($\sigma_{\rm syst.}$). Contributions to the time-dependent systematic errors ($\sigma_{\rm time}$) are from: the trigger efficiency and the reconstruction efficiencies. Contributions to the total systematic error ($\sigma_{\rm syst.}$) are from: the time-dependent systematic error, the background evaluation, the geomagnetic cutoff, the acceptance calculation, the rigidity resolution function, and the absolute rigidity scale.
The days are defined as UTC time 00:00:00 – 23:59:59. The daily collection time of the proton fluxes is $(1.6 - 3.7) \times 10^3 {\rm s}$ at 1 GV, $(4.5 - 7.5) \times 10^3 {\rm s}$ at 2 GV, $(1.8 - 2.3) \times 10^4 {\rm s}$ at 5 GV, $(3.3 - 3.8) \times 10^4 {\rm s}$ at 10 GV, $(6.1 - 7.0) \times 10^4 {\rm s}$ at 20 GV, and, above 0 GV, reaches $(6.7 - 7.3) \times 10^4 {\rm s}$ out of $8.64 \times 10^4 {\rm s}$ per day.