Dr Hayley Bignall
(Joint Institute for VLBI in Europe, Dwingeloo, The Netherlands)
Observations over the last two decades have shown that a significant
fraction of all flat-spectrum, extragalactic radio sources vary in
intensity on timescales of a day or less at observed frequencies of
several GHz. It has been demonstrated that such rapid variations are
predominantly interstellar scintillation (ISS). A few sources show
extremely rapid, intra-hour variations, evidently due to scattering in
very local Galactic turbulence. Observations of ISS can be used to
probe very compact, microarcsecond-scale structure in the inner
jets of radio-loud AGN, as well as turbulence in the ionized
interstellar medium (ISM) of our Galaxy. I will briefly review
methods of extracting microarcsecond-scale "maps" from ISS
observations, and present some new results for the scintillating
quasar PKS 1257-326. I also plan to give a brief summary of some of the
latest developments in this field, based on talks and discussions at a
small workshop being held in the Netherlands in early April.
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