Latest results from AMS uncover secrets of the heliosphere and the cosmos

A unique and unexpected scientific result from Professor Veronica Bindi and her team in the Physics department of the University of Hawai’i at Mānoa has been published in Physical Review Letters in July 31, 2018 (DOI: 10.1103/PhysRevLett.121.051101).

Working around the clock over the past several years, Dr. Bindi, together with Cristina Consolandi, Claudio Corti, and others, have been studying galactic cosmic rays using data from the Alpha Magnetic Spectrometer (AMS) on the International Space Station. Now they can finally reveal new insight into the propagation of cosmic ray particles in the heliosphere.
AMS has just reported accurate monthly proton and helium fluxes over six years, during the maximum of Solar Cycle 24, as a function of energy up to tens of giga-electron-volts (Figure 1). At these energies, cosmic ray propagation in the Heliosphere correlates with solar activity, which changes in time. The AMS result, based on one billion events, reveals that, surprisingly, the proton and helium fluxes have nearly identical fine structures both in time and energy. The data shows that the amplitude of the structures depends on energy and reduces one year after Solar Maximum. Of equal importance, the data shows that the p/He flux ratio is time independent above 3 GV, but has a long-term decrease in the ratio below 3 GV, also starting one year after Solar Maximum (Figure 2). This new AMS result provides unique insights into cosmic ray propagation in the Heliosphere.
Monthly Proton fluxes
Figure 1. The AMS monthly proton (blue) and helium (red) fluxes.
p-HE ratio
Figure 2. The AMS p/He ratio below around 3 GV.

Dr. Bindi said ”It is so rewarding when, after years of study, you find something new and unexpected that challenges your beliefs. It makes you review our current understanding of the field, and it moves scientific knowledge forward”. Dr . Bindi also added “We want to thank our sponsors, especially the NSF (NSF CAREER grant NSF AGS-1455202) and Wyle Laboratories, Inc. (grant NAS 9-02078) for supporting us and giving us the opportunity to perform this important research

More details on Dr. Bindi and her team can be found at:

This work has been sponsored by:

  • Wyle Laboratories, Inc. grant (NAS 9-02078)
  • NASA DATA base grant
  • Heliophysics Living with a Star (NNH14ZD001N-LWS)
  • NSF CAREER grant (NSF AGS-1455202)