The development of instabilities leading to the formation of internal shocks is expected in the relativistic outflows of both gamma–ray bursts and blazars .
The shocks heat the expanding ejecta , generate a tangled magnetic field and accelerate leptons to relativistic energies .
While this scenario has been largely considered for the origin of the spectrum and the fast variability in gamma–ray bursts , here we consider it in the contest of relativistic jets of blazars .
We calculate the expected spectra , light curves and time correlations between emission at different wavelengths .
The dynamical evolution of the wind explains the minimum distance for dissipation ( \sim 10 ^ { 17 } cm ) to avoid \gamma – \gamma collisions and the low radiative efficiency required to transport most of the kinetic energy to the extended radio structures .
The internal shock model allows to follow the evolution of changes , both dynamical and radiative , along the entire jet , from the inner part , where the jet becomes radiative and emits at high energies ( \gamma –jet ) , to the parsec scale , where the emission is mostly in the radio band ( radio–jet ) .