What makes up approximately 90% of the flux in Galactic Cosmic Rays (GCRs)?
Answer
Protons (hydrogen nuclei)
Galactic Cosmic Rays (GCRs) are high-energy particles originating from distant astrophysical events outside the heliosphere. Their composition is specifically known through analysis of the particles that reach us. The flux of GCRs is overwhelmingly dominated by atomic nuclei. Specifically, protons, which are the nuclei of hydrogen atoms, constitute the vast majority, accounting for approximately 90% of the total flux. Following protons in abundance are alpha particles, which are helium nuclei, with only small traces of heavier elements making up the remainder of this energetic stream entering the solar system.
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