Refractive effects in pulsar scintillation

Recent studies have focused attention on the refractive effects of long-wavelength (<or approx. 1014cm) electron density fluctuations in the interstellar medium upon radio observations of pulsars and compact extragalactic radio sources. In earlier work, a simple scattering model was introduced which allowed the computation of fluctuations in mean intensity, image size, pulse width and pulse arrival time, along with their cross-correlations and fluctuation time-scales, when there is a power-law spectrum of density perturbations in a thin 'equivalent screen' of scattering material. In this work, the analysis is extended to include refraction-induced fluctuations in intrinsically diffractive quantities such as the scintillation time-scale and the decorrelation bandwidth. The theory is then used to study the drifting bands in dynamic scintillation spectra caused by the dispersive steering of the diffraction pattern. (author)