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

[46.02] The Galactic Distribution of Electron-density Microturbulence, the Pulsar Distance Scale, and Scintillations of Hypervelocity Neutron Stars

J. M. Cordes (Cornell U.)

I will summarize briefly the radio diagnostic observations that probe density microstructure on scales of 100 km to 100 AU in the interstellar medium. Constraints on the wavenumber spectrum and turbulent velocities will be given. The galactic distribution of free electrons and their fluctuations will be described. I will then focus on how to improve the galactic distribution model and the pulsar distance scale. In particular, I will discuss the galactic center and anticenter and the use of ISS to diagnose the presence of and localize regions of enhanced density along the line of sight (e.g. HII regions, supernova shells and spiral arms). I will then discuss a new hybrid method that combines ISS and VLBI observations of pulsars to measure the space velocities and distances of the fastest neutron stars, particularly those that are more than one density scale height (about 1 kpc) from the galactic plane. Such pulsars are too far to infer a dispersion-measure distance or to measure a VLBI or timing parallax. These fast pulsars are extremely interesting for testing core-collapse mechanisms that probably underlie the fast space velocities. Finally, I will comment briefly on the scintillations to be expected for gamma-ray burst radio afterglows, using the galactic pulsar population to calibrate the scattering from the Galaxy's ISM and from the ISM of intervening galaxies.

Program listing for Tuesday