Flux Density Variation Of Pulsars And Interstellar Scintillation Models

The research on pulsar interstellar scintillation is very active, thanks to the sub-stantive meaning for pulsar research. The integrated pulse profile gives information on the radiation process in the magnetosphere of neutron star, and the variation of the long term flux density demonstrates the property of interstellar medium, e.g the spectrum of the electron density fluctuations and the scattering strength.In chap-ter one, we briefly introduce some background knowledge of the pulsar. Then we outline the theory models and latest progress on pulsar interstellar scintillation in chapter two. We detailed present the two-component interstellar scintillation model in chapter three.The properties of the variation of the long term at the radio flux density have deserved the attentions of the astronomers. They previously considered the variation as pulsar intrinsic inner fluctuation. Recently, they tendency the scintillation phe-nomenon by the interstellar medium refraction. In this paper, we mainly discuss a rigorous treatment of the refractive scintillation caused by a two-component inter-stellar scattering medium at a Kolmogorov form of density spectrum.It is assumed that the scattering of the thin screen is concentrated in a thin layer presented by aδfunction distribution and that the scattering density of the extended irregular medium satisfies the Gaussian distribution. We investigate and develop equations for the flux density structure function corresponding to this two-component interstellar scattering medium geometry in the scattering density distribution and compare our result with the observation. we conclude that the refractive scintillation caused by this two-component interstellar medium scattering gives a more satisfactory expla-nation for the observed flux density variation than does the single extended medium model.The level of refractive scintillation is strongly sensitive to this screen location and is relatively insensitive to the scattering strength of the thin screen medium.This paper uses the two-component interstellar medium scattering model to calcu-late the flux density of the pulsars PSR B2111+46 and PSR B0136+57,and compares the results with the observations. It suggests that the medium consists of a discon-tinuous distribution of plasma turbulence embedded in the interstellar medium. We apply the two-component interstellar medium scattering model to fit, and find that the distribution of density irregularities along the line of sight to the pulsars PSR B2111+46 and PSR B0136+57 fulfills a Kolmogorov form of power spectra, which is well consistent with the conclusions of S2000.