According to recent classifications of averaged pulsar profiles, most pulsar radio observations show "conal" or "coral" radio emissions. Several plasma instabilities are able to provide sufficient coherence to explain the high observed luminosities. In order to come close to reality, we model the pulsar radio emission zone by considering a relativistic beam (or plasma), that flows along curved open field lines, has finite extent perpendicularly to its flow and is bounded by interior and exterior plasma. Analysis of the plasma instabilities that may develop in this system show that besides the radiative and two-stream instabilities, well known in the context of pulsar physics, a "finite beam" instability may arise, that closely depends on the presence of external plasmas. While the two-stream and radiative instabilities appear to be important at some distance of the surface of the star, estimates for the growth rate and polarization of unstable waves resulting from this "new" instability, show that they can play a dominant role near the surface of the neutron star. Thus, as originally proposed by J.M.Rankin (1990), two different emission mechanisms can be simultaneously considered and explain "conal" or "coral" radio emissions.
Joint European and National Astronomical Meeting
- Pub Date: