Measurements of low-energy, re-entrant albedo protons by the HEPD-01 space-borne detector

• Published in: Astroparticle physics Vol. 162; p. 102993
• Main Authors: Martucci, M., Oliva, A., Battiston, R., Beolé, S., Cipollone, P., Contin, A., Cristoforetti, M., De Donato, C., De Santis, C., Di Luca, A., Follega, F.M., Gebbia, G., Iuppa, R., Lega, A., Lolli, M., Masciantonio, G., Mese, M., Neubuser, C., Nicolaidis, R., Nozzoli, F., Osteria, G., Palma, F., Panico, B., Perfetto, F., Perinelli, A., Picozza, P., Ricci, E., Ricci, M., Ricciarini, S.B., Sahnoun, Z., Savino, U., Scotti, V., Sorbara, M., Sotgiu, A., Sparvoli, R., Ubertini, P., Vilona, V., Zoffoli, S., Zuccon, P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2024
• Subjects: Cosmic-rays; Cosmic-rays
• ISSN: 0927-6505; 1873-2852
• DOI: 10.1016/j.astropartphys.2024.102993

Cosmic rays’ interactions with the residual atmosphere surrounding the Earth produce a variety of particles, like electrons, positrons, protons, anti-protons, and Helium nuclei that can be observed below the local geomagnetic cutoff. In this work, we present new measurements of downward-going, albedo proton fluxes with kinetic energy in the range ∼40–∼250 MeV, performed by the High-Energy Particle Detector (HEPD-01) on board of the China Seismo-Electromagnetic Satellite - CSES-01 - at an altitude of ∼500 km. Employing a dedicated trajectory-tracing simulation routine, the protons collected by HEPD-01 are classified into quasi-trapped (QT), long lifetime (≳10 s) particles concentrating in the equatorial region of the Earth, and un-trapped (UT), distributed at all latitudes; the latter includes both precipitating short lifetime particles (UTS) and pseudo-trapped long lifetime (UTL) populations, abundant in the so-called penumbra regions. The temporal trend of re-entrant protons between 2018 and 2022 is also reported, assessing the stability of such population during the data-taking period of HEPD-01; this highlights their independence from the long-term modulating effect of the solar activity. •A study of re-entrant albedo protons in the Earth’s magnetosphere as a function of energy with the HEPD-01 payload is presented.•A comparison with past experiments is carried out, with good results.•Time-profiles of re-entrant albedo protons show a general stability during the analyzed period.