Scattering and diffraction in magnetospheres of fast pulsars

We apply a theory of wave propagation through a turbulent medium to the sca ttering of radio waves in pulsar magnetospheres. We find that under conditi ons of strong density modulation the effects of magnetospheric scintillatio ns in diffractive and refractive regimes may be observable. The most distin ctive feature of the magnetospheric scintillations is their independence of frequency. Results based on diffractive scattering due to small-scale inho mogeneities give a scattering angle that may be as large as 0.1 rad and a t ypical decorrelation time of 10(-8) s. Refractive scattering due to large-s cale inhomogeneities is also possible, with a typical angle of 10(-3) rad a nd a correlation time of the order of 10(-4) s. Temporal variation in the p lasma density may also result in a delay time of the order of 10(-4) s. The different scaling of the above quantifies with frequency may allow one to distinguish the effects of propagation through a pulsar magnetosphere from the interstellar medium. In particular, we expect that the magnetospheric s cintillations are relatively more important for nearby pulsars when observe d at high frequencies. If confirmed, these results would provide a direct t esting of the plasma inside the light cylinder.