The Effect of Interplanetary Scintillation on Epoch of Reionisation
  Power Spectra
  Interplanetary Scintillation (IPS) induces intensity fluctuations in small
angular size astronomical radio sources via the distortive effects of spatially
and temporally varying electron density associated with outflows from the Sun.
These radio sources are a potential foreground contaminant signal for
redshifted HI emission from the Epoch of Reionisation (EoR) because they yield
time-dependent flux density variations in bright extragalactic point sources.
Contamination from foreground continuum sources complicates efforts to
discriminate the cosmological signal from other sources in the sky. In IPS, at
large angles from the Sun applicable to EoR observations, weak scattering
induces spatially and temporally correlated fluctuations in the measured flux
density of sources in the field, potentially affecting the detectability of the
EoR signal by inducing non-static variations in the signal strength. In this
work, we explore the impact of interplanetary weak scintillation on EoR power
spectrum measurements, accounting for the instrumental spatial and temporal
sampling. We use published power spectra of electron density fluctuations and
parameters of EoR experiments to derive the IPS power spectrum in the
wavenumber phase space of EoR power spectrum measurements. The contrast of IPS
power to expected cosmological power is used as a metric to assess the impact
of IPS. We show that IPS has a different spectral structure to power from
foregrounds alone, but the additional leakage into the EoR observation
parameter space is negligible under typical IPS conditions, unless data are
used from deep within the foreground contamination region.
