Study of the Solar Modulation and Heliospheric Propagation of Galactic Cosmic Rays with AMS-02

Abstract:

AMS-02 is a high-precision general-purpose magnetic spectrometer installed on the International Space Station on May 2011 to investigate fundamental questions shared by physics, astrophysics and cosmology on the origin and structure of the Universe, looking for antimatter and dark matter. The travel of cosmic rays through the heliosphere is disturbed by the magnetic field of the Sun which is known to vary with a period of 11 years; this induces a solar modulation in the propagation of cosmic rays which affects their fluxes up to few tens of GeV, modifying the shape and the intensity of the local interstellar spectrum (LIS). The monthly fluxes of protons detected by AMS-02 in the first three years of data taking will be shown. Using the framework of the force-field approximation, the solar modulation parameter will be extracted from the time dependent proton fluxes measured by AMS-02 (2011-2014) and PAMELA (2006-2009); the proton flux from Voyager 1 (October-November 2012) will be assumed as the LIS. The results will be compared with the modulation parameter inferred from the neutron monitors. The limitations of the force-field approximation and the differences between the minimum and the maximum of the solar cycle will be discussed. The availability of cosmic ray modulation data directly from space will be very useful to the heliophysics community, to understand in more details the long term solar activity during an entire solar cycle.