Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998arep...42..766s&link_type=abstract
Astronomy Reports, Volume 42, Issue 6, November 1998, pp.766-778
Astronomy and Astrophysics
Astronomy
19
Scientific paper
A theory for refractive scintillations of pulsars is developed for two types of spectra for electron-density fluctuations in the interstellar medium: power-law and piecewise power-law with a break. Expressions for the refractive-scintillation parameters are obtained for the cases of a uniform distribution of inhomogeneities along the line of sight, a phase screen, and a medium localized near the source or the observer. Comparison of the theory and five-year observations of flux variations for 21 pulsars at 610 MHz shows that the interstellar medium is highly nonuniform at dispersion measures DM > 30 pc/ cm3. Variations of scintillation parameters are determined mainly by electron-density variations, rather than the distance to the source. We present a way to estimate the location and thickness of the effective layer of turbulent medium that gives rise to the observed scintillations. Scintillation parameters are estimated for the observed pulsars. Two types of spectra are realized in the interstellar medium: pure power-law and piecewise power-law with a break. The spectral break corresponds to the characteristic scale l ~= 3 x 10^10 cm. Pure power-law spectra are realized when there is a diffuse medium filling nearly uniformly all of space along the line of sight, while spectra with a break are typical when there is a medium with compact features localized near the source.
Shishov V. I.
Smirnova Tatiana V.
Stinebring Daniel R.
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