3-11 July 2007
Merida, Mexico
Mexico/General timezone
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Contribution Oral

Merida, Mexico - Gran Salon Yucatan (Fiesta Americana)

Transition from galactic to extragalactic cosmic rays

Speakers

  • Dr. Veniamin BEREZINSKY

Primary authors

Abstract content

Despite the radical change of origin, the transition from galactic to extragalactic cosmic rays (CR) is not well established and not well understood. In principle three important characteristics of CR, spectrum, chemical composition and anisotropy, must change at energy of transition. The spectrum is naturally changing from steep to flat component. The end of galactic CR is characterised by steep spectrum with exponent \gamma ~ 3.1. If transition is natural, the extragalactic spectrum must be flatter. For rigidity-acceleration or rigidity-propagation models the end of galactic CR must be presented
by the heaviest nuclei, most probably by iron. The transition should be characterised by changing the mass composition from heaviest to the light nuclei, like proton and helium. In the end of galactic CR spectrum the anisotropy should be noticeable, while for extragalactic CR isotropic distribution is more natural. There are two features in the observed spectrum, where the transition may occur: the ankle, the flattening of the spectrum at energy ~10 EeV, and the
second knee at energy 0.4 - 08~EeV. Two classes of models describing transition at these two energies will be reviewed.