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Published August 1, 2015 | Published + Submitted
Journal Article Open

Pulsar Observations of Extreme Scattering Events

Abstract

Extreme scattering events (ESEs) in the interstellar medium (ISM) were first observed in regular flux measurements of compact extragalactic sources. They are characterized by a flux variation over a period of weeks, suggesting the passage of a "diverging plasma lens" across the line of sight (LOS). Modeling the refraction of such a lens indicates that the structure size must be of the order of AU and the electron density of the order of 10s of cm^(−3). Similar structures have been observed in measurements of pulsar intensity scintillation and group delay. Here we report observations of two ESEs, showing increases in both intensity scintillation and dispersion made with the Parkes Pulsar Timing Array. These allow us to make more complete models of the ESE, including an estimate of the "outer-scale" of the turbulence in the plasma lens. These observations clearly show that the ESE structure is fully turbulent on an AU scale. They provide some support for the idea that the structures are extended along the LOS, such as would be the case for a scattering shell. The dispersion measurements also show a variety of AU scale structures that would not be called ESEs, yet involve electron density variations typical of ESEs and likely have the same origin.

Additional Information

© 2015 American Astronomical Society. Received 2015 May 18; accepted 2015 June 20; published 2015 July 27. The Parkes radio telescope is part of the Australia Telescope, which is funded by the Commonwealth Government for operation as a National Facility managed by CSIRO. S.O. is supported by the Alexander von Humboldt Foundation.

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Published - Coles_2016p113.pdf

Submitted - 1506.07948v1.pdf

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August 22, 2023
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