Galactic Cosmic-Ray Hydrogen Spectra in the 40-250 MeV Range Measured by the High-energy Particle Detector (HEPD) on board the CSES-01 Satellite between 2018 and 2020

The High-energy Particle Detector (HEPD) on board the China Seismo-Electromagnetic Satellite (CSES-01) - launched on 2018 February 2 - is a light and compact payload suitable for measuring electrons (3-100 MeV), protons (30-250 MeV), and light nuclei (up to a few hundreds of MeV). The Sun-synchronous orbit and large acceptance allow HEPD to measure cosmic-ray particles near the ±65° latitude limit for a fair amount of time per day. In this work, three semiannual galactic hydrogen energy spectra between ∼40 and 250 MeV are presented, including a comparison with theoretical spectra from HelMod, a 2D Monte Carlo model developed to simulate the solar modulation of cosmic rays throughout the heliosphere. To our knowledge, these are the first hydrogen energy spectra below 250 MeV measured at 1 au between 2018 and 2020. © 2020. The Author(s). Published by the American Astronomical Society..