Luke DruryDublin Institute for Advanced Studies

Luke DruryDublin Institute for Advanced Studies

Particle Acceleration in the Universe

Particle Acceleration in the Universe

Moscow 1987

Adelaide 1990

Leeds 1991

Dublin 1991 (birth of Auger project)

Some ICRC history...

The US president was George Bush;

War broke out in the Gulf!

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:

Not statistically significant, but....

In the heliosphere

in the Galaxy

at cosmological scales

Particle acceleration in the Universe

Universal phenomenon - seen:

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Very common sequence...

Sudden release of energy

Mass ejection

Shock formation

Particle acceleration

CMEs, SNRs, GRBs etc...

Supersonic flow

Hits obstacle

Shock forms

Particle acceleration

Other common pattern....

Earth’s bow shock, pulsar wind, AGN jets etc..

Cas-A as seen in X-

rays by Chandra

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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.

Not the only game in town....

Magnetic reconnection

Second-order Fermi

Large E fields (pulsars?)

But seems to be the most important one....

Ambient compressed?

Amplified?

Self-generated?

However, need a (non-uniform) magnetic field....

Ambient field

SNR

Field amplification

McKenzie and Voelk, 1982Bell and Lucek, 2001Lucek and Bell, 2001Bell, 2004

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.

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

Faster acceleration

Higher cut-off energies

Greater radiative losses for electrons

Stronger magnetic fields mean....

but also...

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...)

Conclusions

The problem of the origin of cosmic rays will be solved by more work

and less talk!Rutherford, ca 1940