Stars and scintillations  [slides]

Abstract

Our understanding of radio-wave propagation through interstellar space is evolving rapidly in response to new observational results. It now appears that radio-wave scattering is caused primarily by dense plasma organised in radial filaments around hot stars. The resulting picture of the circumstellar plasma environment looks much like the Helix Nebula, where ionised filaments arise as the cometary tails of tiny molecular clouds. I'll describe the observational developments and their interpretation, and I'll sketch some broad astrophysical implications.