Slow pulsar scintillation and the spectrum of interstellar electron density fluctuations1

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Abstract
Intensity fluctuations in pulsars are commonly ascribed to scintillations produced by electron density inhomogeneities in the interstellar medium. The power spectrum of the inhomogeneities is believed to be a power law, q−β with β = 11/3 (Kolmogorov spectrum). The spectrum of intensity fluctuations produced by a thin phase-changing screen has already been worked out for the case 2<ββ4 than for β4, the intensity fluctuations are essentially independent of the strength of the phase fluctuations on the screen and thus independent of the wavelength of observation λ or the distance D of the pulsar. In contrast, for β4. Several arguments have been presented in the past, based on the observed wavelength dependence of decorrelation bandwidth, image size, scintillation time-scale, etc. to support the Kolmogorov value β = 11/3. We show that these observations are equally consistent with β>4. If β>4, the observations require the power-law spectrum to extend over only a small range of scales ∼1012–1015 cm compared to ∼109–1015 cm required in the case of a Kolmogorov spectrum.

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