Observational Validation of Cosmic Ray Acceleration Hypothesis

Despite centuries of rigorous theoretical and observational research, the origin and acceleration mechanism of Galactic Cosmic Rays (GCRs) remain a mystery. In 1949, Fermi proposed a diffusive shock acceleration model that includes a prominent mechanism for GCR acceleration. However, observational evidence, on the other hand, remains elusive. Here, we provided the first apparent verification of GCR acceleration at 1 AU using measurements from the CRIS instrument onboard the ACE spacecraft.