Numerical modeling of galactic cosmic ray proton and helium observed by AMS-02 during the solar maximum of Solar Cycle 24

Abstract

Galactic cosmic rays (GCRs) are affected by solar modulation while they propagate through the heliosphere. The study of the time variation of GCR spectra observed at Earth can shed light on the underlying physical processes, specifically diffusion and particle drifts. Recently, the AMS-02 experiment measured with very high accuracy the time variation of the cosmic ray proton and helium flux between May 2011 and May 2017 in the rigidity range from 1 to 60 GV. In this work, a comprehensive three-dimensional (3D) steady-state numerical model is used to solve Parker's transport equation and is used to reproduce the monthly proton fluxes observed by AMS-02. We find that the rigidity slope of the perpendicular mean free path above 4 GV remains constant, while below 4 GV it increases during solar maximum. Assuming the same mean free paths for helium and protons, the models are able to reproduce the time behavior of the p/He ratio observed by AMS-02. The dependence of the diffusion tensor on the particle mass-to-charge ratio, A/Z, is found to be the main cause of the time dependence of p/He below 3 GV.

arXiv comment21 pages, 8 figures, 3 tables, accepted for publication in The Astrophysical Journal

References in corpus (27)

• PAMELA results on the cosmic-ray antiproton flux from 60 MeV to 180 GeV in kinetic energy
• Pulsars as the Sources of High Energy Cosmic Ray Positrons
• Solar Modulation of Cosmic Rays
• The cosmic-ray positron energy spectrum measured by PAMELA
• Time dependence of the proton flux measured by PAMELA during the July 2006 - December 2009 solar minimum
• Constraints on WIMP Dark Matter from the High Energy PAMELA $\bar{p}/p$ data
• CRDB: a database of charged cosmic rays
• Modulation of galactic protons in the heliosphere during the unusual solar minimum of 2006 to 2009
• Cosmic Ray Transport in the Galaxy: a Review
• High-energy antiprotons from old supernova remnants
• AMS02 results support the secondary origin of cosmic ray positrons
• Proton fluxes measured by the PAMELA experiment from the minimum to the maximum solar activity for the 24th solar cycle
• Solar Modulation of the Proton Local Interstellar Spectrum with AMS-02, Voyager 1 and PAMELA
• Antiproton constraints on the GeV gamma-ray excess: a comprehensive analysis
• Constraints on particle dark matter from cosmic-ray antiprotons
• Measurements of Cosmic-Ray Hydrogen and Helium Isotopes with the PAMELA experiment
• Isotopic Composition of Light Nuclei in Cosmic Rays: Results from AMS-01
• Very local interstellar spectra for galactic electrons, protons and helium
• Modulation of galactic cosmic rays during the unusual solar minimum between cycles 23 and 24
• Evidence for a Time Lag in Solar Modulation of Galactic Cosmic Rays
• Dark matter searches with cosmic antideuterons: status and perspectives
• New local interstellar spectra for protons, Helium and Carbon derived from PAMELA and Voyager 1 observations
• Solar and nuclear physics uncertainties in cosmic-ray propagation
• Testing diffusion of cosmic rays in the heliosphere with proton and helium data from AMS
• The effect of magnetic field modifications on the modulation of cosmic rays in the heliosphere
• Systematic study of the uncertainties in fitting the cosmic positron data by AMS-02
• Sudden Intensity Increases and Radial Gradient Changes of Cosmic Ray MeV Electrons and Protons Observed at Voyager 1 beyond 111 AU in the Heliosheath

Cited by in corpus (24)

• Low energy cosmic rays
• Numerical modeling of cosmic rays in the heliosphere: Analysis of proton data from AMS-02 and PAMELA
• Modeling of Heliospheric Modulation of Cosmic-ray Positrons in a Very Quiet Heliosphere
• Time dependence of the flux of helium nuclei in cosmic rays measured by the PAMELA experiment between July 2006 and December 2009
• Time-dependent AMS-02 electron-positron fluxes in an extended force-field model
• Time and Charge-Sign Dependence of the Heliospheric Modulation of Cosmic Rays
• Time dependent solar modulation of cosmic rays from solar minimum to solar maximum
• Numerical modeling of cosmic-ray transport in the heliosphere and interpretation of the proton-to-helium ratio in Solar Cycle 24
• Helium fluxes measured by the PAMELA experiment from the minimum to the maximum solar activity for solar cycle 24
• Evolution of coronal mass ejections and the corresponding Forbush decreases: modelling vs multi-spacecraft observations
• Unfolding Drift Effects for Cosmic Rays over the Period of the Sun's Magnetic Field Reversal
• Radial Evolution of the April 2020 Stealth Coronal Mass Ejection between 0.8 and 1 AU -- A Comparison of Forbush Decreases at Solar Orbiter and Earth
• Recurrent galactic cosmic-ray flux modulation in L1 and geomagnetic activity during the declining phase of the solar cycle 24
• Local interstellar spectra and solar modulation of cosmic ray electrons and positrons
• Local interstellar spectra and solar modulation of cosmic ray proton and Helium
• Using Cosmic Rays detected by HST as Geophysical Markers I: Detection and Characterization of Cosmic Rays
• Constraining the Charge-, Time- and Rigidity-Dependence of Cosmic-Ray Solar Modulation with AMS-02 Observations during Solar Cycle 24
• Modulation of cosmic ray anti-protons in the heliosphere: simulations for a solar cycle
• Solar modulation of AMS-02 daily proton and Helium fluxes with modified force field approximation models
• Current status and new perspectives on cosmic ray deuterons
• Data driven analysis of cosmic rays in the heliosphere: diffusion of cosmic protons
• Propagation Times and Energy Losses of Cosmic Protons and Antiprotons in Interplanetary Space
• Probing solar modulation of AMS-02 time-dependent D, ${}^3$He and ${}^4$He fluxes with modified force field approximation
• First Observations of Solar Halo Gamma Rays Over a Full Solar Cycle