Cosmic ray acceleration at relativistic shocks, shear layers, .

Understand

A review of theoretical results on cosmic ray first-order Fermi acceleration at relativistic shock waves is presented, with recent results substantially changing the existing knowledge on these processes.

• In particular one can not expect such shocks to form particle distributions extending to very high energies.
• Instead, distributions with the shock compressed injected component followed by a more or less extended high energy tail are usually created.
• Increasing the shock Lorentz factor leads to steepening of the energetic tail.