SMuK 2023 – scientific programme

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EP: Fachverband Extraterrestrische Physik

EP 9: Poster

EP 9.13: Poster

Wednesday, March 22, 2023, 17:30–19:00, HSZ OG1

Extending SOHO-EPHINs energy range for Helium nuclei — •Malte Hörlöck, Bernd Heber, Patrick Kühl, and Stefan Jensen — Christian-Albrechts-Universität zu Kiel

Galactic cosmic rays are composed mainly of protons, helium nuclei and electrons. The flux of these particles is modulated due to the heliospheric magnetic field that shields lower energy particles from the heliosphere. Hence, the flux depends on the solar activity. During phases of low and high solar activity, a maximum and minimum in the flux is observed, respectively. The SOlar and Heliospheric Observatory (SOHO) was launched in 1995. The Electron Proton Helium INstrument (EPHIN) onboard SOHO is a particle telescope, consisting of a stack of 6 silicon semiconductor detectors surrounded by an anticoincidence detector. The instrument stops protons and helium nuclei up to energies of 51 MeV/nucleon. At higher energies, these particles penetrate the telescope. As shown previously EPHIN provides sufficient information to obtain the flux of protons up to an energy of about a GeV. Here we investigate the instrument capabilities to obtain helium fluxes for energies above 51 MeV/nucleon using the dE/dx-dE/dx-method. However, the task is hampered by the fact that two detectors became noisy in 1998 and 2017, respectively. Thus, extensive modeling utilizing the GEANT4 package is needed in order to derive helium fluxes up to about 100 MeV/nucleon.