13-16 February 2012
CERN
Europe/Zurich timezone

Transition from Galactic to Extragalactic Cosmic Rays and cosmic ray anisotropy

15 Feb 2012, 12:30
20m
500/1-001 - Main Auditorium (CERN)

500/1-001 - Main Auditorium

CERN

CERN, Geneva
400
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Speaker

Dmitri Semikoz (A)

Description

We constrain the energy at which the transition from Galactic to extragalactic cosmic rays occurs by computing the anisotropy at Earth of cosmic rays emitted by Galactic sources. Since the diffusion approximation starts to loose its validity for E/Z >10^(16-17) eV, we propagate individual cosmic rays using Galactic magnetic field models and taking into account both their regular and turbulent components. The turbulent field is generated on a nested grid which allows spatial resolution down to fractions of a parsec. If the primary composition is mostly light or intermediate around E ~ 10^18 eV, the transition at the ankle is ruled out, except in the unlikely case of an extreme Galactic magnetic field with strength >~ 10 {\mu}G. Therefore, the fast rising proton contribution suggested by KASCADE-Grande data between 10^17 eV and 10^18 eV should be of extragalactic origin. In case heavy nuclei dominate the flux at E >~ 10^18 eV, the transition energy can be close to the ankle, if Galactic cosmic rays are produced by sufficiently frequent transients as e.g. magnetars.

Primary author

Co-authors

Prof. Guenter Sigl (University of Hamburg) Dr Gwenael Giacinti (NTNU Norway) Prof. Michael Kachelriess (NTNU Norway)

Presentation Materials