On the nature of pulsar radio emission

A theory of pulsar radio emission generation, in which the observed waves a re produced directly by maser-type plasma instabilities operating at the an omalous cyclotron-Cherenkov resonance omega - k(parallel to)v(parallel to) + omega(B)/gamma(res) = 0 and the Cherenkov drift resonance omega - k(paral lel to)v(parallel to) - k(perpendicular to)u(d) = 0, is capable of explaini ng the main observational characteristics of pulsar radio emission. The ins tabilities are due to the interaction of the fast particles from the primar y beam and the tail of the distribution with the normal modes of a strongly magnetized one-dimensional electron-positron plasma. The waves emitted at these resonances are vacuum-like, electromagnetic waves that may leave the magnetosphere directly, In this model, the cyclotron-Cherenkov instability is responsible for the core-emission pattern and the Cherenkov drift instab ility produces conal emission. The conditions for the development of the cy clotron-Cherenkov instability are satisfied for both typical and millisecon d pulsars provided that the streaming energy of the bulk plasma is not very high gamma(p) approximate to 10, In a typical pulsar the cyclotron-Cherenk ov and Cherenkov drift resonances occur in the outer parts of the magnetosp here at r(res) approximate to 10(9) cm, This theory can account for various aspects of pulsar phenomenology, including the morphology of the pulses, t heir polarization properties and their spectral behaviour. We propose sever al observational tests for the theory. The most prominent prediction is the high altitudes of the emission region and the linear polarization of conal emission in the plane orthogonal to the local osculating plane of the magn etic field.