Despite notable improvements made in the last decades, the characterization of the near-Earth
proton radiation environment is still incomplete, with major uncertainties affecting the description
of high-energy particles (¡50 MeV) in the South Atlantic Anomaly (SAA) region. The High-
Energy Particle Detector (HEPD) on board the China Seismo-Electromagnetic Satellite (CSES-
01), launched on February 2018 on a Low-Earth Orbit and with an altitude of about 507 km,
is a light and compact payload suitable for measuring electrons (3-100 MeV), protons (30-300
MeV), and light nuclei (up to a few hundreds of MeV) with a high energy resolution and a wide
angular acceptance. Thanks to its good identification performance, it can carry out precise and
comprehensive measurement of particle fluxes, including angular information. The observations
of HEPD could be fundamental not only for space weather purposes, but because they could help
set important constraints on trapping and interaction processes in the Earth’s atmosphere and
magnetosphere. Furthermore, they enable the testing and validation of current theoretical and
empirical models of the inner radiation belt, like the NASA AP9. In this contribution, we report a
preliminary analysis of ¡30 MeV protons detected inside the SAA region between 2018 and 2021.