Quasilinear theory of Cherenkov-drift instability.

We examine linear and quasiliner stages of Cherenkov-drift instability developed in the relativistic magnetized electron-positron plasma penetrated by ultrarelativistic beam of electrons (or positrons). The plasma flow is streaming along the slightly curved magnetic field lines. In this case, the curvature drift of beam particles plays a decisive role in the development of the instability. A quasilinear relaxation of Cherenkov-drift instability leads to diffusion of resonant particles in momenta space. The expressions for diffusion coefficients of Cherenkov-drift instability are obtained. The numerical estimations are carried out for the parameters of relativistic magnetized plasma of pulsar magnetospheres providing a test of validity of the approximations used in our approach.