Revisiting the structure function of PSR B0950+08 scintillations

TL;DR

This paper reinterprets the structure function of PSR B0950+08 scintillations, suggesting the observed deviations are consistent with Kolmogorov turbulence or compressive turbulence, implying the presence of thin ionized scattering screens.

Contribution

It offers a new interpretation of scintillation data, proposing that the apparent deviation from Kolmogorov turbulence is due to the finite depth of the turbulent region.

Findings

The observations are consistent with Kolmogorov turbulence when considering the turbulence region depth.

The fitted index of 1 can also indicate compressive turbulence with a smaller depth.

Estimates support the existence of thin ionized scattering screens in the local interstellar cloud.

Abstract

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.