Annual Cosmic Ray Spectra from 250 MeV up to 1.6 GeV from 1995 - 2014 Measured With the Electron Proton Helium Instrument onboard SOHO

Abstract

The solar modulation of galactic cosmic rays (GCR) can be studied in detail by examining long-term variations of the GCR energy spectrum (e.g. on the scales of a solar cycle). With almost 20 years of data, the Electron Proton Helium INstrument (EPHIN) onboard the SOlar and Heliospheric Observatory (SOHO) is well suited for this kind of investigation. Although the design of the instrument is optimized to measure proton and helium isotope spectra up to 50 MeV nucleon${}^{-1}$ , the capability exists to determine proton energy spectra from 250 MeV up to above 1.6 GeV. Therefore we developed a sophisticated inversion method to calculate such proton spectra. The method relies on a GEANT4 Monte Carlo simulation of the instrument and a simplified spacecraft model that calculates the energy-response function of EPHIN for electrons, protons and heavier ions. For validation purposes, proton spectra based on this method are compared to various balloon missions and space instrumentation. As a result we present annual galactic cosmic ray spectra from 1995 to 2014.

References in corpus (7)

• The Solar Cycle
• Solar Modulation of Cosmic Rays
• Time dependence of the proton flux measured by PAMELA during the July 2006 - December 2009 solar minimum
• Measurements of 0.2 to 20 GeV/n cosmic-ray proton and helium spectra from 1997 through 2002 with the BESS spectrometer
• Modulation of galactic protons in the heliosphere during the unusual solar minimum of 2006 to 2009
• Time dependence of the e^- flux measured by PAMELA during the July 2006 - December 2009 solar minimum
• Measurements of cosmic-ray proton and helium spectra from the BESS-Polar long-duration balloon flights over Antarctica

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