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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:
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
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
QuickTime™ and aPhoto decompressor
are needed to see this picture.
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