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Particle Acceleration in the Universe

Particle Acceleration in the Universe. Luke Drury Dublin Institute for Advanced Studies. Some ICRC history. Moscow 1987 Adelaide 1990 Leeds 1991 Dublin 1991 (birth of Auger project).

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Particle Acceleration in the Universe

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  1. Particle Acceleration in the Universe • Luke Drury • Dublin Institute for Advanced Studies

  2. Some ICRC history... • Moscow 1987 • Adelaide 1990 • Leeds 1991 • Dublin 1991 (birth of Auger project)

  3. After the 1991 ICRC I said we would never again hold another meeting of more than 100 people. However, last year we cohosted with Armagh Observatory the NAM2003 meeting, also ca 500 participants. On both occasions: • The US president was George Bush; • War broke out in the Gulf! Not statistically significant, but....

  4. Particle acceleration in the Universe Universal phenomenon - seen: • In the heliosphere • in the Galaxy • at cosmological scales

  5. Very common sequence... Sudden release of energy Mass ejection Shock formation Particle acceleration CMEs, SNRs, GRBs etc...

  6. Other common pattern.... Supersonic flow Hits obstacle Shock forms Particle acceleration Earth’s bow shock, pulsar wind, AGN jets etc..

  7. Cas-A as seen in X-rays by Chandra

  8. Shock acceleration... Non-relativistic version reasonably well understood. Injection still a problem. Nonlinear effects difficult to include in models, but generally good agreement. Considerable progress on relativistic case.

  9. Not the only game in town.... • Magnetic reconnection • Second-order Fermi • Large E fields (pulsars?) But seems to be the most important one....

  10. Ambient compressed? • Amplified? • Self-generated? However, need a (non-uniform) magnetic field....

  11. Ambient field SNR

  12. Field amplification McKenzie and Voelk, 1982 Bell and Lucek, 2001 Lucek and Bell, 2001 Bell, 2004

  13. Field generation Frederiksen, J T et al, 2004, ApJ 608 L13. Califano, F et al, 1998, Phys Rev E, 57, 7048. Weibel, E 1959, PRL 2 83.

  14. Growing evidence for enhanced magnetic fields in young SNRs. • GRB models assume strong fields. • Equipartition fields seem to work in AGN hot-spots. • Plausible mechanisms exist

  15. Faster acceleration • Higher cut-off energies • Greater radiative losses for electrons Stronger magnetic fields mean.... but also...

  16. Conclusions • Shock acceleration seems OK if we allow field amplification by shocks. • There are other possibilities though... • Need more and better data (over to you, Alan...)

  17. The problem of the origin of cosmic rays will be solved by more work and less talk! Rutherford, ca 1940

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