Refractive Interstellar Scintillation for Flux Density Variations of Two Pulsars

The flux density structure functions of PSRs B0525+21 and B2111+46 are calculated with the refractive interstellar scintillation (RISS) theory. The theoretical curves are in good agreement with observations Astrophys. J. 539 (2000) 300 (hereafter S2000). The spectra of the electron density fluctuations both are of Kolmogorov spectra. We suggest that the flux density variations observed for these two pulsars are attributed to refractive interstellar scintillation, not to intrinsic variability.