# Acceleration and Interaction of Ultra High Energy Cosmic Rays

**Authors:** R. J. Protheroe  
**arXiv:** [astro-ph/9812055](https://arxiv.org/abs/astro-ph/9812055)  
**Date:** 1998-12-03  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/astro-ph--9812055v1/

## Key points

- Shock acceleration is explored in depth for ultra high energy cosmic rays
- Maximum energies achievable and spectrum characteristics near cut-off are discussed
- Interactions of high-energy cosmic rays with background radiation and resulting electron-photon cascade are examined
- Potential sources of highest energy cosmic rays include active galaxies, gamma ray bursts, and topological defects
- Protheroe argues against the necessity of exotic models like emission by topological defects to explain existing data
- Shock acceleration at Fanaroff-Riley Class II radio galaxies may offer a plausible explanation for observed phenomena
- Further research is essential to confirm the origins of ultra high energy particles in nature
- New cosmic ray data and improved estimates of extragalactic radiation fields and magnetic fields are crucial for a comprehensive understanding

## Summary

In this chapter by R. J. Protheroe, the author provides an in-depth exploration of shock acceleration and its implications for ultra high energy cosmic rays. The discussion delves into the maximum energies achievable through this process and examines the characteristics of the spectrum near cut-off. The interactions of high energy cosmic rays with background radiation are also examined, along with their propagation and resulting electron-photon cascade. The author considers potential sources of the highest energy cosmic rays, including active galaxies, gamma ray bursts, and topological defects. While the origin of these particles remains uncertain, Protheroe argues against the necessity of invoking exotic models such as emission by topological defects to explain existing data. Instead, he suggests that shock acceleration at Fanaroff-Riley Class II radio galaxies may offer a plausible explanation for observed phenomena. However, Protheroe emphasizes that further research is essential to confirm the origins of these ultra high energy particles in nature. New cosmic ray data and improved estimates of extragalactic radiation fields and magnetic fields will be crucial in providing a comprehensive understanding of this intriguing aspect of astrophysics. This chapter serves as a valuable contribution to the field of cosmic-ray astrophysics and highlights the ongoing quest to unravel the mysteries surrounding ultra high energy cosmic rays.