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Properties of Daily Helium Fluxes

  • (AMS Collaboration)
  • CIEMAT
  • RWTH Aachen University
  • National Institute for Nuclear Physics
  • Laboratório de Instrumentação e Física Experimental de Partículas
  • Jülich Research Centre
  • CERN
  • University of Groningen
  • National Institute for Subatomic Physics
  • University of Trento
  • Massachusetts Institute of Technology
  • University of Perugia
  • University of Hawai'i at Mānoa
  • NASA Johnson Space Center
  • University of Rome La Sapienza
  • University of Geneva
  • Kiel University
  • National Research Council of Italy
  • Academia Sinica - Institute of Physics
  • CAS - Institute of High Energy Physics
  • University of Chinese Academy of Sciences
  • Shandong Institute of Advanced Technology
  • Université Grenoble Alpes
  • University of Bologna
  • Shandong University
  • Middle East Technical University

Research output: Contribution to journalArticlepeer-review

51 Scopus citations

Abstract

We present the precision measurement of 2824 daily helium fluxes in cosmic rays from May 20, 2011 to October 29, 2019 in the rigidity interval from 1.71 to 100 GV based on 7.6×108 helium nuclei collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The helium flux and the helium to proton flux ratio exhibit variations on multiple timescales. In nearly all the time intervals from 2014 to 2018, we observed recurrent helium 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. In the entire time period, we found that below ∼7 GV the helium flux exhibits larger time variations than the proton flux, and above ∼7 GV the helium to proton flux ratio is time independent. Remarkably, below 2.4 GV a hysteresis between the helium to proton flux ratio and the helium flux was observed at greater than the 7σ level. This shows that at low rigidity the modulation of the helium to proton flux ratio is different before and after the solar maximum in 2014.

Original languageEnglish
Article number231102
JournalPhysical Review Letters
Volume128
Issue number23
DOIs
StatePublished - 10 Jun 2022

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