# The Physics of UHECRs: Spectra, Composition and the Transition Galactic-Extragalactic

## TL;DR

This paper reviews experimental evidence on ultra high energy cosmic rays, focusing on their flux, composition, and the transition from galactic to extragalactic origins, linking observations with theoretical models.

## Contribution

It provides a comprehensive overview of current experimental data and discusses the transition between galactic and extragalactic cosmic rays in detail.

## Key findings

- Evidence supports a transition from galactic to extragalactic cosmic rays.
- Composition measurements suggest a change in particle types at high energies.
- Spectral features align with theoretical models of cosmic ray sources.

## Abstract

We review the experimental evidences about flux and mass composition of ultra high energy cosmic rays in connection with theoretical scenarios concerning astrophysical sources. In this context, we also address the discussion about the expected transition between cosmic rays produced inside the Galaxy and those coming from the intergalactic space.