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A possible mechanism for the explanation of pulsar subpulse drift is suggested. In the region of the open magnetic field lines the existence of an electron-positron plasma penetrated by a primary particle beam is assumed. There is a possibility of excitation of large-scale drift waves propagating transversely to the magnetic field lines. These waves can affect the fulfilment of the radio-wave generation conditions. If the pulsar angular velocity is near to the frequency of the drift waves one should observe regular drift phenomena.

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The generation of radio waves in the plasma of the pulsar magnetosphere is considered taking into account the inhomogeneity of the dipole magnetic field. It is shown that the growth rate of the instability of the electromagnetic waves calculated in the non-resonance case turns out to be of the order of 1/ TO (where TO is the time of plasma escape from the light cylinder). However, the generation of electromagnetic waves from a new type Cherenkov resonance is possible, occurring when the particles have transverse velocities caused by the drift due to the inhomogeneity of the magnetic field. Estimates show that the development of this type of instability is possible only for pulsars with ages which exceed 104 yr. We make an attempt to explain some peculiarities of 'typical' pulsar emission on the basis of the model developed.

At present there exist several well-grounded models of pulsar radiation which do not exactly coincide with each other [e.g. Ruderman and Sutherland (1975), Cheng and Ruderman (1980), Arons and Sharlemann (1979), Arons (1981)]. The creation of a dense, relativistic, electron-positron plasma in the polar regions of rotating neutron star magnetospheres is the point of similarity between these models. Surely the pulsar radiation should be generated in such a plasma. The plasma density near the stellar surface is np ≃ 1016 e to 1017cm–3, and the average Lorentz-factor of the particles is γp = 3 to 10. The plasma is penetrated by the beam of “primary” electrons, extracted from the stellar surface and accelerated by the electric field. The beam parameters are as follows: nb = 7 x 10–2B0P–1, where P is the pulsar period and B0 magnetic field at the stellar surface and γb = 3 x 106 to 107.