Cherenkov-drift emission mechanism

Emission of a charged particle propagating in a medium with a curved magnetic field is reconsidered stressing the analogy between this emission mechanism and collective Cherenkov-type plasma emission. It is explained how this mechanism differs from conventional Cherenkov, cyclotron or curvature emission and how it includes, to some extent, the features of each of these mechanisms. Presence of a medium supporting subluminous waves is essential for the possibility of wave amplification by particles streaming along the curved magnetic field with a finite curvature drift. We suggest an analogy between the curvature drift emission and the anomalous cyclotron-Cherenkov emission. Treating the emission in cylindrical coordinates in the plane-wave-like approximation allows one to compute the single particle emissivity and growth rate of the Cherenkov-drift instability. We compare the growth rates calculated using the single particle emissivity and using the dielectric tensor of one dimensional plasma streaming along the curved field. In calculating the single particle emissivity it is essential to know the normal modes of the medium and their polarization which can be found from the dielectric tensor of the medium. This emission mechanism may be important for the problem of pulsar radio emission generation

Nature of microstructure in pulsar radio emission

We present a model for microstructure in pulsar radio emission. We propose that micropulses result from the alteration of the radio wave generation region by nearly transverse drift waves propagating across the pulsar magnetic field and encircling the bundle of the open magnetic field lines. It is demonstrated that such waves can modify significantly curvature of these dipolar field lines. This in turn affects strongly fulfillment of the resonance conditions necessary for the excitation of radio waves. The time-scale of micropulses is therefore determined by the wavelength of drift waves. Main features of the microstructure are naturally explained in the frame of this model.Comment: 4 pages, submitted to MNRAS Letter