Nature of microstructure in pulsar radio emission

We present a model for microstructure in pulsar radio emission. We propose that micropulses result from alteration of the radio wave generation region by nearly transverse drift waves propagating across the pulsar magnetic fi eld and encircling the bundle of the open magnetic field lines. It is demon strated that such waves can modify the curvature of the field lines signifi cantly. This, in turn, affects strongly fulfilment of the resonance conditi ons necessary for the excitation of radio waves. The time-scale of micropul ses is therefore determined by the wavelength of the drift waves. The main features of the microstructure are naturally explained within the framework of this model.