- Abstract Relativistic shocks are present in a number of objects where violent processes are accompanied by relativistic outflows of plasma. The magnetization parameter σ= B 2/4π nmc 2 of the ambient medium varies in wide range. Shocks with low σ are expected to substantially enhance the magnetic fields in the shock front. In non-relativistic shocks the magnetic compression is limited by nonlinear effects related to the deceleration of flow. Two- fluid analysis of perpendicular relativistic shocks shows that the nonlinearities are suppressed for σ≪ 1 and the magnetic field reaches nearly equipartition values when the magnetic energy density is of the order of the ion energy density, B eq 2~ 4π nm ic 2 γ. A large cross-shock potential eφ/mic 2 γ 0~ B 2/B eq 2 develops across the electron–ion shock front. This potential is responsible for electron energization.