In 1949, Fermi proposed a model for the acceleration of cosmic rays through particle collisions with magnetic clouds in the interstellar medium. This process, known as the "Second Order Fermi Mechanism", increases particle energy during head-on collisions, resulting in a steady gain in energy. A later model to produce Fermi Acceleration was generated by a powerful shock front moving through space. Particles that repeatedly cross the front of the shock can gain significant increases in energy. This became known as the "First Order Fermi Mechanism".
In 1949 Fermi proposed a model for the acceleration of cosmic rays through particle collisions with magnetic clouds in the interstellar medium This process known as the "Second Order Fermi Mechanism" increases particle energy during head-on collisions resulting in a steady gain in energy A later model to produce Fermi Acceleration was generated by a powerful shock front moving through space Particles that repeatedly cross the front of the shock can gain significant increases in energy This became known as the "First Order Fermi Mechanism"