Acceleration of particles by shocks in high Beta plasmas

The plasma shock drift process is discussed; it is shown that for hyperkinetic particles this effect is already included in diffusive shock acceleration. Reaction effects are mentioned. Particles experience small energy changes on interaction with shock fronts, the exception being at quasiperpendicular shocks where slow energetic particles can be reflected with large energy gains. However if particles can interact many times through diffusive scattering the final effect is large and leads to powerlaw tails in the distribution function and ultimately to major dynamical effects on the shock structure.