!!!! Bat A, salle de réunion 601 du 6ième étage !!!!
COSMIC RAYS BEYOND THE KNEE
Peter L. BIERMANN
MPI Bonn
Résumé :
Standard shock acceleration in the Interstellar Medium leads to energies
far below the feature in the cosmic ray spectrum usually referred to as
the knee, at $3 \, 10^{15}$ eV, where the spectrum bends down by about
1/3. There is one proposal published that links this feature to the
explosion of very massive stars, red supergiants and Wolf Rayet stars.
In this proposal the knee is predicted to be at near $Z \; 10^{15}$ eV
approximnately, and the ankle, where the spectrum is in transition to
the extragalactic component, at $Z \; 3 \; 10^{17}$ eV, where $Z$ is the
charge of the nucleus. The spectrum is predicted to be $E^{-2.67}$ below
the knee, and $E^{-3.07}$ above the knee, with some expected error
range.
The observed features, at knee and ankle are so well defined that the
critical $E/Z$ ratio must be very well defined in Nature, and be common
to all sites contributing to our cosmic ray population. This then leads
back to the argument by Kardashev (1964} that supernovae are powered by
potential energy, and that the energy is transmitted from rotation via
magnetic fields to the outside; this argument can be made quantitative.
Considering then the abundances of cosmic rays this proposal requires
that very massive stars explode with $10^{52}$ ergs, rather more than
usually assumed. This is easily explained in Kardashev's picture, as
angular momentum loss during the star's evolution leads to a higher
explosion energy naturally. This then leads to a final concept that
directly connects Gamma Ray Bursts with supernovae. Tests will be the
abundances of the various chemical elements in cosmic rays, the fraction
of anti-protons, and the precise spectrum at knee and ankle.
