IDV from Interstellar Subimaging

C.R. Gwinn

I suggest that IDV results from interference of scattered subimages.
Stinebring and collaborators suggest that such subimages, separated in
angle from the primary scattering disk, provide a simple explanation
for the substructure seen in scintillation spectra of scattered
pulsars. PSR J0437-4715, at an angular separation of only 10 deg from
the the celebrated IDV source PKS 0405-385, usually shows such
substructure.  The fundamental scattering seen for this pulsar is far
too weak to contribute to IDV of the extragalactic source. However,
the observed subimaging could produce IDV. The pulsar lies at a
distance of 140 pc, beyond the infered IDV screen. Simple theoretical
arguments suggest that subimaging can produce the observed
nearly-sinusoidal intensity variations, and that source size can
easily select for subimaging within tens of pc of the observer. I
discuss observational tests of this hypothesis, and theoretical models
for turbulence that predict common subimaging in a natural way.