On hand of 3D PIC simulations we show that in a strongly
magnetized plasma a relativistic electron beam can be forced
to emit highly coherent radio emission by self-induced nonlinear
density fluctuations. Such slowly moving nonlinear structures
oscillate with the local plasma frequency at which the relativistic
electrons are scattered. Beam electrons dissipate a significant
amount of their kinetic energy by inverse Compton radiation
at a frequency of about γ2ωpe. Since
the beam is sliced into pancake structures which experience
the same electric field the inverse Compton scattering is coherent.
Such a process is a very promising candidate for the coherent
radio emission of pulsars.