Abstract
Abstract 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.
Highlights
Hydrogen nuclei are the most abundant components of charged galactic cosmic rays (CRs); they represent approximately 90% of the total CR budget and, together with helium nuclei, they account for ∼99% of the cosmic radiation
We present three semiannual cosmic-ray hydrogen spectra measured by the High-energy Particle Detector (HEPD) in the ∼40–250 MeV range, during the period between the very end of the 24th solar cycle and the beginning of the 25th—from 2018 August to 2020 January
Throughout the analysis presented in this paper, the region of the SAA16 was excluded to avoid saturation or pile-up issues that may occur under extremely high particle rates
Summary
Hydrogen nuclei (protons) are the most abundant components of charged galactic cosmic rays (CRs); they represent approximately 90% of the total CR budget and, together with helium nuclei, they account for ∼99% of the cosmic radiation. Evidence that the majority of CRs are accelerated in supernova remnants (SNRs) in the Galaxy are compelling, yet they are still inferred in an indirect way—see Baade & Zwicky (1934), Ginzburg & Syrovatsky (1961), Ackermann et al (2013), Tavani et al (2010), Giordano et al (2012), Acciari et al (2011), Berezhko & Völk (2007), and Vink (2012) From their site of production and acceleration, CRs propagate through the Galaxy interacting with the interstellar medium and diffusing on the permeating magnetic field before reaching the Earth’s solar system (Amato & Blasi 2018). We present three semiannual cosmic-ray hydrogen spectra measured by the High-energy Particle Detector (HEPD) in the ∼40–250 MeV range, during the period between the very end of the 24th solar cycle and the beginning of the 25th—from 2018 August to 2020 January. A deeper look at mission objectives and satellite characteristics can be found in Shen et al (2018)
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