29 July 2015 to 6 August 2015
World Forum
Europe/Amsterdam timezone

The solar modulation potential derived by spacecraft measurements modified to describe GCRs at energies below neutron monitors and above

4 Aug 2015, 14:45
Mississippi (World Forum)


World Forum

Churchillplein 10 2517 JW Den Haag The Netherlands
Oral contribution SH-EX Parallel SH 07 Modulation I


Jan Gieseler (University of Kiel)


Galactic Cosmic Rays (GCRs) are modulated by various effects as they propagate through the heliosphere before they are detected at Earth. This transport can be described by the Parker equation (Parker, 1965). It calculates the phase space distribution of GCRs depending on the main modulation processes: convection, drifts, diffusion and adiabatic energy changes. A first order approximation of this equation is the force field approach, reducing it to a one-parameter dependency, the solar modulation potential. Utilizing this approach, Usoskin et al. (2005; 2011) reconstructed the solar modulation potential between 1936 and 2010, which by now is commonly used in many fields. However, it has been shown previously e.g. by Herbst et al. (2010) that the solar modulation potential depends not only on the Local Interstellar Spectrum (LIS) but also on the energy range of interest. Using the LIS by Usoskin et al. (2005) together with published proton intensity spectra obtained by PAMELA, heavier nuclei measurements from IMP8 and ACE/CRIS as well as neutron monitors, we have investigated this energy dependence further. We will present the results that show as expected severe limitations at lower energies including a strong dependence on the solar magnetic epoch. Based on these findings, we will outline a tool to describe GCR proton spectra in the energy range from a few hundred MeV to tens of GeV over the last solar cycles.
Collaboration -- not specified --
Registration number following "ICRC2015-I/" 0818

Primary author

Jan Gieseler (University of Kiel)


Prof. Bernd Heber (University of Kiel) Dr Konstantin Herbst (University of Kiel)

Presentation Materials