Speaker
Jörg Paul Rachen
(IMAPP / Radboud University Nijmegen)
Description
It seems to be a striking coincidence that all putative cosmic ray
sources which are dynamically able to fill the universe with the observed
extragalactic cosmic ray density can produce the same maximum confinement
energy, eBR ~ 10^20 eV, while being spread in scale R over 10 orders of
magnitude - the most impressive representation of this coincidence is the famous
Hillas plot, in which all "interesting" sources of extragalactic cosmic rays
fall on one line. We present here a potential explanation for this, by assuming
that cosmic ray production is a byproduct of the generation of turbulence during
the gravitational contraction of the Universe, i.e. structure formation. The
model naturally explains why the maximum confinement energy is scale invariant,
while reproducing BOTH the value of the maximum energy (~10^20 eV) and the
overall extragalactic production rate, ~10^47 erg / Mpc^3 / year for a
production spectral index of E^-2.3, from known cosmological parameters plus ONE
free parameter, which is the fraction of gravitational energy transformed into
turbulence and found to be close to its canonical expectation value. While the
generic approach presented here can certainly not compete with detailed modeling
of specific cosmic ray sources, it predicts the fractional energetic
contribution of sources acting at different scales, and can thus serve as a
theoretical prior for extragalactic cosmic ray production in Bayesian modeling
of the large scale Galactic Magnetic Field from UHECR arrival directions.
Primary author
Jörg Paul Rachen
(IMAPP / Radboud University Nijmegen)
