Propagation of cosmic rays in heliosphere: The HELMOD model

Abstract

The heliospheric modulation model HELMOD is a two dimensional treatment dealing with the helio-colatitude and radial distance from Sun and is employed to solve the transport-equation for the GCR propagation through the heliosphere down to Earth. This work presents the current version 3 of the HELMOD model and reviews how main processes involved in GCR propagation were implemented. The treatment includes the so-called particle drift effects - e.g., those resulting, for instance, from the extension of the neutral current sheet inside the heliosphere and from the curvature and gradient of the IMF -, which affect the transport of particles entering the solar cavity as a function of their charge sign. The HELMOD model is capable to provide modulated spectra which well agree within the experimental errors with those measured by AMS-01, BESS, PAMELA and AMS-02 during the solar cycles 23 and 24. Furthermore, the counting rate measured by Ulysses at ± 80 ° of solar latitude and 1-5 AU was also found in agreement with that expected by HELMOD code version 3.