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Refractive effects in pulsar scintillation

Romani, Roger W. and Narayan, Ramesh and Blandford, Roger (1986) Refractive effects in pulsar scintillation. Monthly Notices of the Royal Astronomical Society, 220 (1). pp. 19-49. ISSN 0035-8711. doi:10.1093/mnras/220.1.19.

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Recent studies have focused attention on the refractive effects of long-wavelength (≲ 10^(14) cm) electron density fluctuations in the interstellar medium upon radio observations of pulsars and compact extragalactic radio sources. In earlier work, a simple scattering model was introduced which allowed us to compute fluctuations in mean intensity, image size, pulse width and pulse arrival time, along with their cross-correlations and fluctuation time-scales, when there is a power-law spectrum of density perturbations in a thin ‘equivalent screen’ of scattering material. In this work, we extend the analysis to include refraction-induced fluctuations in intrinsically diffractive quantities such as the scintillation time-scale, t_s, and the decorrelation bandwidth, ν_(dc). We then use the theory to study the drifting bands in dynamic scintillation spectra caused by the dispersive steering of the diffraction pattern. We also estimate the fluctuations in the position of the image on the sky, rates of variation of intensity and position, and the root mean square elongation of the scatter-broadened image. We make two further extensions of the theory. First we show that, despite certain formal divergences, the theory can be extended to accommodate steeper density fluctuation spectra (power-law indices β > 4) than the conventionally assumed Kolmogorov spectrum (β = 11/3). Secondly, we test the validity of the thin-screen approximation, developing a formalism to treat scattering in an extended medium. We find that the thin-screen theory sometimes underestimates the refractive fluctuations by a factor ∼2. The auto- and cross-correlations of the various observables are calculated and comparison is made with the known scintillation properties of pulsars to select those effects most suited to observational verification. The predicted cross-correlation between decorrelation bandwidth and flux fluctuations seems particularly suitable for this purpose. These measurements should, in turn, provide insights into the density fluctuation spectrum and the distribution of the scattering along the line-of-sight.

Item Type:Article
Related URLs:
URLURL TypeDescription
Romani, Roger W.0000-0001-6711-3286
Narayan, Ramesh0000-0002-1919-2730
Blandford, Roger0000-0002-1854-5506
Additional Information:© 1986 Royal Astronomical Society. Provided by the NASA Astrophysics Data System. Accepted 1985 October 24. Received 1985 October 14; in original form 1985 May 13. We thank J. Goodman for numerous discussions and D. Backer for advice on observations of the galactic centre. Support for this work was provided by the National Science Foundation under grant AST 84-15355. RWR is grateful to the Fannie and John Hertz Foundation for fellowship support.
Funding AgencyGrant Number
NSFAST 84-15355
Fannie and John Hertz FoundationUNSPECIFIED
Issue or Number:1
Record Number:CaltechAUTHORS:20190523-125439587
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Official Citation:Roger W. Romani, Ramesh Narayan, Roger Blandford, Refractive effects in pulsar scintillation, Monthly Notices of the Royal Astronomical Society, Volume 220, Issue 1, 1 May 1986, Pages 19–49,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95757
Deposited By: George Porter
Deposited On:23 May 2019 21:59
Last Modified:16 Nov 2021 17:15

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