The Optics of Refractive Substructure

Understand

Newly recognized effects of refractive scattering in the ionized interstellar medium have broad implications for very long baseline interferometry (VLBI) at extreme angular resolutions.

• Building upon work by Blandford & Narayan (1985), we present a simplified, geometrical optics framework, which enables rapid, semi-analytic estimates of refractive scattering effects.
• We show that these estimates exactly reproduce previous results based on a more rigorous statistical formulation.
• We then derive new expressions for the scattering-induced fluctuations of VLBI observables such as closure phase, and we demonstrate how to calculate the fluctuations for arbitrary quantities of interest using a Monte Carlo technique.