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The Heliospheric Modulation Model

Online Calculator

Version Test

Proton High AMS02 small

Website latest update on September 28, 2022

Welcome to HelMod Website supported within the framework of space radiation environment activities of  ASIF, i.e., ASI (Italian Space Agency) Supported Irradiation Facilities. The helmod website was initially created in February 2012. In these pages, you can find information about the Solar Modulation Model for the propagation of Galactic Cosmic Rays through the Heliosphere from the Heliopause down to Earth.

As advertised on the GALPROP website, HelMod website can be used as a service package to seamlessly calculate the effects of the heliospheric modulation for GALPROP output files.

HelMod is a 2D Monte Carlo model to simulate the solar modulation of galactic cosmic rays. The model is based on the Parker transport equation which contains diffusion, convection, particle drift and energy loss. Following the evolution of the solar activity in time, we are able to modulate the local interstellar spectra (LIS) of cosmic ray species, assuming their isotropy beyond the termination shock, down to the Earth's location inside the heliosphere.

The current HelMod Version is the result of a continuous development since 1998 (Monte-Carlo approach to Galactic Cosmic Ray propagation in the Heliosphere, Nucl. Phys B-Proc Sup). The latest review on HelMod was published in 2018 (Propagation of Cosmic Rays in Heliosphere: the HelMod Model. Adv. Space Res. 62(10):2859 - 2879, 2018)

In the present website version, a solar modulation calculator is available for Cosmic Rays experiments carried out during solar Cycle 23 and 24.

In the 2D-HelMod code version 1 was implemented the standard Parker field with modification in the polar region, the dependence on the particle drift, the Solar Wind description revisited for high and low activity periods, the Heliosphere divided in regions related to spatial propagation of turbulence from Sun, and, finally, it was introduced the possibility to evaluate solar modulation for electrons and positrons.

From version 2  the heliospheric magnetic field  and the spatial dependence of parallel diffusion coefficient revisited according to Ulysses measurements of time variation cosmic rays counting rate to account for different latitudinal gradients in opposite solar polarities

From version 3.0 The numerical scheme was revisited and a backward-in-time approach was adopted. The rigidity dependence of parallel diffusion coefficient revisited according to PAMELA and AMS-02 data. Introduced the possibility of evaluating solar modulation of ions. Developed an additional python module to link GALPROP LIS (and plain text file) with HelMod results. 

From version 3.2 A systematic cross-check between Solar Modulator and Online Calculator was performed for proton, antiproton and helium.

From version 3.4 Online version is aligned with the published model in Boschini et al 2017. and the Solar Modulator for Ions is available.

In HelMod, from version 3.5.0 it is implemented a forecasting capability for protons and ions fluxes, which will result in a better GCR flux estimation for future space missions (e.g., see asif website).

From version 4.0 the time-dependent Termination Shock and Heliopause is included in the model.

Relevant result pictures from HelMod publications can be found on the Results page.

This project is part of the activities involving also HelMod / geomagsphere /sr-niel / ASIF /AMS-02 Milano-Bicocca (Italy) group and IEP-SAS space physic (Kosice, Slovakia). Local Interstellar Spectra (LISs) used in HelMod are those obtained from the join GalProp-HelMod effort.

Following ASIF implementation agreements 2017-22-HD.0 ASI-ENEA, 2017-15-HD.0 ASI-INFN, 2021-39-HH.0 ASI-ENEA, 2021-36 HH.0 ASI-University of Milano-Bicocca and 2024-21-HH ASI-INFN implementation agreement involving ASI and INFN, the ASIF and ASIF gateway websites, the sr-nielhelmod and geomagsphere websites are mantained within the space radiation environment activities of ASIF framework. Their websevers are handled by means of ASIF support center at the Physics Department of Milano-Bicocca University and are operated by virtual server in VDC (Virtual Data Center) environment at the Italian Space AgencyASI

For any comment, remark and suggestion, please contact us by email  This email address is being protected from spambots. You need JavaScript enabled to view it.

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Example of modulated spectrum for Proton for the period corresponding to AMS-02 Averaged data [Boschini et al. 2017]



No Warranty. THE SOFTWARE IS PROVIDED "AS IS" AND WITHOUT WARRANTY OF ANY KIND. Simulation results are public domain. Developers and maintainers of HelMod-4, and respective institutions, shall have no liability for the use of HelMod-4 products. For official space qualification purposes please refer to space agency requirements.