2014 Hoyle medal and prize

Professor Anthony Raymond Bell, University of Oxford and Rutherford Appleton Laboratory. For elucidating the origin and impact of cosmic rays and for his seminal contributions to electron energy transport in laboratory plasmas

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During the course of his career Tony Bell has opened up new research fields in both astrophysical and laboratory plasmas. He has played a leading role in the development of what is now the standard model of astrophysical particle acceleration and cosmic ray (CR) origins through the publication of two landmark papers.

The process of diffusive shock acceleration was independently proposed by Bell and by three other research groups. The theory of diffusive shock acceleration rapidly gained acceptance as the most common source of energetic particles in the universe. The theory is robust and predicts a universal power law in agreement with observations. Shock-accelerated particles radiate in wavebands extending from the radio to gamma-rays and form one of the main windows on both Galactic and extra-galactic astrophysics, as well as being an important feature of the heliosphere.

The theory of magnetic field amplification was proposed by Bell alone. It solved a 25 year old puzzle of how cosmic rays could be accelerated to the knee, the characteristic bend in the Galactic cosmic ray distribution at PeV energies when existing theories predicted a maximum energy 100 times lower. The theory is confirmed by the observation of large magnetic fields, particularly associated with supernova remnant shocks.

Bell’s contribution to astrophysics is informed by his work on laboratory plasmas, where he has also made many seminal contributions, particularly to the understanding of the astrophysically related topics of energetic particle transport, magnetic field generation and QED effects in future experiments with high power lasers.