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Session 46 - Interstellar Scattering and Scintillation as Tools in Radio Astronomy.
Topical, Oral session, Tuesday, June 09

[46.06] Interstellar Medium from Refractive Scintillation of Pulsars

T. V. Smirnova, V. I. Shishov (Astro Space Center, Lebedev Physics Inst., Moscow, Russia)

We developed the theory of refractive scintillations for pulsar emission for two types of spectra of electronic density fluctuations in the interstellar medium: a power spectrum, and a piece-power spectrum. We have obtained expressions for the parameters of the refractive scintillations for the cases of a uniform distribution of electron density irregularities along the line of sight, for a phase screen, for the medium irregularities being located close to the pulsar, and to the observer. Based on the data from 5 years of observations of the variation of the flux of 21 pulsars at the frequency of 610MHz we show that the interstellar medium for DM > 30 pc/cm^3 is very inhomogenous, and variations of the scintillation parameters are mainly due to variations of the electron density, and are not due to the distance to the source. We show how we can estimate the location of the effective layer of the turbulent medium responsible for the scintillations, as well as the thickness of the layer. These parameters were computed for the observed pulsars. We show also that in the interstellar medium there are two type of spectra: a power spectrum, and a piece-power spectrum. The characteristic scale at which the break happens in the spectrum is l\sim=3*10^10cm. We also show that a pure power spectrum happens in a diffuse medium which is filled approximately uniformly along the line of sight, and the spectrum with a break happens in the medium where there are compact regions with an increased electron density.

Program listing for Tuesday