Distribution of plasma turbulence in our Galaxy derived from radio scintillation maps

Abstract

THE scattering of radio waves by plasma turbulence in the Galaxy is analogous to the scintillation of starlight due to the Earth's atmosphere, and similarly leads to a broadening of the apparent angular sizes of extragalactic radio sources1–3, as well as the smearing out of pulsar pulse profiles. Previous investigations of the galactic plasma turbulence using these effects have suggested a monotonic increase in plasma turbulence towards the galactic plane4–6 and towards the centre7,8. Here I present a new map of galactic plasma turbulence derived from the results of a recent interplanetary scintillation radio survey9, using a method of analysis based on the angular size distribution of radio sources. The map reveals that structure persists to high galactic latitudes, and that it agrees with the morphology of the soft X-ray background. These results suggest that the solar neighbourhood is encapsulated in an envelope of plasma turbulence, most probably the relic of the supernova explosion of a nearby massive star.