Revisiting the structure function of PSR B0950+08 scintillations

The observational structure function of the scintillations of the radio pulsar PSR B0950+08, was fitted, a decade ago, with a power law with index $1 \pm 0.01$. This was interpreted as an {\em appreciable deviation} from the, commonly observed index of $5/3$, expected for Kolmogorov turbulence. In this paper it is suggested that the observations are consistent with a Kolmogorov turbulence and that the {\em apparent} deviation is due to a turbulent region with an effective depth which is {\em comparable} to the observed lateral scales on the plane of the sky, spanned by the pulsar beam. Alternatively, the fitted index of $1$ is consistent with an underlying compressive turbulence and an even {\it smaller} depth. In the first interpretation the depth is $(5.5 \pm 1.8) \times 10^8 cm$. In the second one, the depth is $\lesssim 4\times 10^7 cm$. These estimates lend support for the existence of extremely thin, ionized scattering screens in the local interstellar cloud, that have been proposed a decade ago.