  Although the solar wind flows primarily outward from the Sun to
interplanetary space, there are times when small-scale plasma inflows are
observed. Inward-propagating density fluctuations in polar coronal holes were
detected by the COR2 coronagraph on board the STEREO-A spacecraft at
heliocentric distances of 7 to 12 solar radii, and these fluctuations appear to
undergo substantial deceleration as they move closer to the Sun. Models of
linear magnetohydrodynamic waves have not been able to explain these
deceleration patterns, so they have been interpreted more recently as jets from
coronal sites of magnetic reconnection. In this paper, we develop a range of
dynamical models of discrete plasma parcels with the goal of better
understanding the observed deceleration trend. We found that parcels with a
constant mass do not behave like the observed flows, and neither do parcels
undergoing ablative mass loss. However, parcels that accrete mass in a
snowplow-like fashion can become decelerated as observed. We also extrapolated
OMNI in situ data down to the so-called Alfven surface and found that the
initial launch-point for the observed parcels may often be above this critical
radius. In other words, in order for the parcels to flow back down to the Sun,
their initial speeds are probably somewhat nonlinear (i.e., supra-Alfvenic) and
thus the parcels may be associated with structures such as shocks, jets, or
shear instabilities.
